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General Forums => Aircraft and Vehicles => Topic started by: Stoney74 on August 17, 2007, 09:18:01 AM

Title: P-51 Airfoil and Turn Performance
Post by: Stoney74 on August 17, 2007, 09:18:01 AM
I know the Pony was supposed to have a "laminar flow" wing, but I don't know what airfoil it had exactly.  What I do know is that some of the uncambered 6-series NACA airfoils at low thickness/chord ratios have some relatively poor Clmax numbers.  I'm assuming that someone knows the airfoil used on the Pony, and also the t/c ratio for the wing.  

If my above thoughts are true, can it be safe to assume that the airfoil shape/type may have one of the reasons that the Pony's slow speed turn performance in the game is comparitively poor?  

From a general aviation perspective, I know Mooney's and Grumman's with 6-series airfoils have some quirky/poor slow-speed handling and stall characteristics, even though they use 15% t/c with design lift coefficients of .4.  If the Pony used a thinner airfoil with less camber, seems like it may suffer drag penalties at slower speeds or high AoA maneuvers.

(I've been geeking out on airfoil books lately)...
Title: P-51 Airfoil and Turn Performance
Post by: gripen on August 17, 2007, 01:21:07 PM
Some sources (like NACA papers) claim the profiles of the P-51 as "North American-NACA compromise" sections while some others claim sections as NACA 45-100. AIAA-91-3288 by Lednicer&Gilchrist gives t/c 16,55% at root (without leading edge extension) and 11,44% at tip.

Theoretically the first laminar profiles had a lower Clmax values than the earlier profiles but in practice the P-51 reached quite similar Clmax values at low mach numbers as other WWII fighters  ie around 1,3. At higher mach numbers the P-51 did relatively well.

But read your self:

http://hdl.handle.net/2060/19930092575

http://hdl.handle.net/2060/19930093805

http://hdl.handle.net/2060/19930084610

And there is a bit more but I'm too lazy to dig them out...
Title: P-51 Airfoil and Turn Performance
Post by: AquaShrimp on August 17, 2007, 01:32:37 PM
Translate this into laymans terms please.  What is clMax?
Title: P-51 Airfoil and Turn Performance
Post by: gripen on August 17, 2007, 01:36:57 PM
eeh...

Cl = lift coefficient
Clmax = maximum lift coefficient

clMax = second cousin of the Mad Max  :)
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 17, 2007, 01:49:35 PM
I lean toward the Lednicer/Gilchrist airfoil quotations that Gripen notes.  

In their modern CFD eval of the P-51 as they tried to identify the airfoil they eventually ended up spending time with Ed Horker (sp??) who was a NAA designer for the Mustang and provided them the definitive answer on the Mustang airfoil along with the engineering drawings.  The airfoil was an NAA airfoil modified from a NACA spec.

----------
On the turn performance complaint I'm not sure the issue is the Mustang's turn performance clean, but sustained turn with flaps deployed.  Widewing will have to clarify.  

With all due respect to Widewing, I'm not ready to agree there is a problem in this regard.  I think HiTech has stated that it's an issue of which data source to use in this particular case.

The funny thing is that there are other things I've mulled over (for a long long time now!) from a turn performance standpoint for the Mustang that gripen is aware of but alas I've not reached any definitive conclusion on it!

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 02:46:13 PM
Quote
Originally posted by dtango

On the turn performance complaint I'm not sure the issue is the Mustang's turn performance clean, but sustained turn with flaps deployed.  Widewing will have to clarify.  

With all due respect to Widewing, I'm not ready to agree there is a problem in this regard.  I think HiTech has stated that it's an issue of which data source to use in this particular case.

The funny thing is that there are other things I've mulled over (for a long long time now!) from a turn performance standpoint for the Mustang that gripen is aware of but alas I've not reached any definitive conclusion on it!

Tango, XO
412th FS Braunco Mustangs


Have a look at this graphic and tell me if you think that a 13,457 lb P-47D-25 should out-turn a fuel light, 8,604 lb P-51B.

That's 44.9 lb per sq/ft wing loading fighter turning smaller circles than a 36.9 lb per sq/ft wing loading fighter.

(http://home.att.net/~c.c.jordan/Relative-Turn-Rate-and-Radius.jpg)

I can't find a single test reference that supports what we see here. Something is clearly incorrect.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: evenhaim on August 17, 2007, 02:52:19 PM
Would this have to do with last year's FM update?

cheers
-freezman
Title: P-51 Airfoil and Turn Performance
Post by: Benny Moore on August 17, 2007, 02:54:11 PM
Quote
Originally posted by Widewing
That's 44.9 lb per sq/ft wing loading fighter turning smaller circles than a 36.9 lb per sq/ft wing loading fighter.


While such things can easily be explained by differences in flaps, power, wing shape, and other factors, you're quite right; all of the tests I've seen say that the P-51 should definitely out-turn a P-47 and should turn almost as well as a Spitfire, though not as tight as a P-38 (provided that the P-38 is using the maneuver setting for its Fowler flaps).
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 03:02:51 PM
Quote
Originally posted by evenhaim
Would this have to do with last year's FM update?

cheers
-freezman


Several updates have contributed... The last one around June of 2006 was the capper.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: SteveBailey on August 17, 2007, 03:11:00 PM
Quote
Originally posted by Widewing
Several updates have contributed... The last one around June of 2006 was the capper.

My regards,

Widewing



I'd like to know why HT ignores this... any answers?
Title: P-51 Airfoil and Turn Performance
Post by: Kweassa on August 17, 2007, 03:15:37 PM
Quote
I'd like to know why HT ignores this... any answers?


 They need definate proof, Steve.
Title: P-51 Airfoil and Turn Performance
Post by: bozon on August 17, 2007, 03:32:42 PM
WW are these circles with full flaps? Is this how the P51 turns or is it just effect of the flaps?

My gut feeling is that our flap drag penalty is too low for the extreme settings. Perhaps too much stability near stall and easy recovery too. I hate the flap-o-rama that dogfighting has become. In a way, I'd wish that all planes would get the old 109 instability and the Mosquito's tail slide stall. That would put an end to the silly hanging on the prop with full flaps till you fall backwards, and the full flaps 80 mph turning circles while eating a sandwich.
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 03:39:25 PM
Quote
Originally posted by SteveBailey
I'd like to know why HT ignores this... any answers?


Well, here's the same test done in AH1 (1.11 patch 4) added to the graphic. Yes, I still AH1 on my machine. ;)

Note the smaller circle and faster turn rate (overlap of the trail). Note that the issue is magnified by the P-51s getting worse, and many of the other fighters getting better.

(http://home.att.net/~c.c.jordan/Relative-Turn-Rate-and-RadiusAH1.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 03:49:09 PM
Quote
Originally posted by bozon
WW are these circles with full flaps? Is this how the P51 turns or is it just effect of the flaps?
 


These tests were done at about 50 feet ASL, and with flaps fully deployed. At least 6 full circles were flown to stabilize the aircraft at their limits.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: gripen on August 17, 2007, 04:03:15 PM
BTW here (http://hdl.handle.net/2060/19930092728) is something tested on the P-47 as well.
Title: P-51 Airfoil and Turn Performance
Post by: Krusty on August 17, 2007, 04:17:16 PM
Quote
Originally posted by gripen
BTW here (http://hdl.handle.net/2060/19930092728) is something tested on the P-47 as well.


The P-47C compared to the P-47D11 is probably as different as the P47D11 is to the P-47D40.

The XP-51 is probably as different from the P-51B as the P-51B is from the P-51D. Keep in mind the early mustangs had different wing roots and other changes in their airframe.


It's nice, but I don't think it applies. Those versions are too early to compare to the later models.

EDIT: Maybe the 47 is pretty close, on second thought. The 51 wing changed between early models and later ones, though.
Title: P-51 Airfoil and Turn Performance
Post by: gripen on August 17, 2007, 04:21:54 PM
If you care to read the docs posted, you will find out that there is data on P-51B as well as on P-51D.
Title: P-51 Airfoil and Turn Performance
Post by: Krusty on August 17, 2007, 04:29:13 PM
Still reading it. Seems to mention XP-51, SB2C-1, and P-41C-1. Mentions an XF2 in passing, but no P-51Bs or Ds in the text
Title: P-51 Airfoil and Turn Performance
Post by: gripen on August 17, 2007, 04:31:31 PM
Take the second of the first three docs I posted.
Title: P-51 Airfoil and Turn Performance
Post by: Krusty on August 17, 2007, 04:35:49 PM
Ah, you misunderstand. I was referring only to the one I quoted.
Quote
Originally posted by gripen
BTW here (http://hdl.handle.net/2060/19930092728) is something tested on the P-47 as well.

That one.
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 05:04:03 PM
Here's the same chart with the P-47D-25 and P-51D tested without flaps for reference.

(http://home.att.net/~c.c.jordan/Relative-Turn-Rate-and-RadiusAH1-AH2.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Viking on August 17, 2007, 05:24:12 PM
Quote
Originally posted by Benny Moore
While such things can easily be explained by differences in flaps, power, wing shape, and other factors, you're quite right; all of the tests I've seen say that the P-51 should definitely out-turn a P-47 and should turn almost as well as a Spitfire, though not as tight as a P-38 (provided that the P-38 is using the maneuver setting for its Fowler flaps).


BS! :lol
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 06:22:37 PM
I tested the Bf 109K-4 with no flaps and full flaps. I have compared the results to the P-51D.

You will note that the turn radius clean is virtually identical, as is the turn rate. However, when flaps are deployed, the 109K-4 gains a large advantage in radius and turn rate. Inasmuch as these aircraft used a similar flap layout, I find it troubling that the Mustang is so badly hampered by what appears to be a unique issue with drag rise.

(http://home.att.net/~c.c.jordan/P-51v109G-4-Turn.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 17, 2007, 08:10:11 PM
A correction on my part, HT talking about different sources of data was on an entirely different topic and not this one.

---------------------

Widewing:

I absolutely agree with you regarding the differences in wingloading if we were discussing instantaneous turn performance between the P-51 and P-47 for the weights you quoted.

We're talking about sustained turn performance however.  Here's the turn radius equation in terms of L/D, T/W, and V:

(http://brauncomustangs.org/images/turn_radius.jpg)

You can see that in a sustained turn Cl (and thus wingloading) is only part of the equation when considering radii for sustained turns.  Drag (Cd) and thrust factor into it as well, not just wingloading.

Pure speculation on my part but with flaps popped maybe the reason the P-47 has a smaller sustained turn radius compared to the Mustang is because of the better cl/cd ratio of the Jug because of it's slotted flaps vs. the Mustang's plain flaps and the 2300hp of the Jug vs. the 1720hp of the Pony.

The only turn radius data for the Mustang I've seen posted was the figure you have that shows the Mustang turn radius compared to the Meteor, etc.  Unfortunately I've never seen any other key details of that report (e.g. config of the aircraft, alt tested, weights, engine power output etc.) that tell me what they were doing that resulted in the data for the turn radii.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 08:51:54 PM
Quote
Originally posted by dtango
A correction on my part, HT talking about different sources of data was on an entirely different topic and not this one.

---------------------

Widewing:

I absolutely agree with you regarding the differences in wingloading if we were discussing instantaneous turn performance between the P-51 and P-47 for the weights you quoted.

We're talking about sustained turn performance however.  Here's the turn radius equation in terms of L/D, T/W, and V:

(http://brauncomustangs.org/images/turn_radius.jpg)

You can see that in a sustained turn Cl (and thus wingloading) is only part of the equation when considering radii for sustained turns.  Drag (Cd) and thrust factor into it as well, not just wingloading.

Pure speculation on my part but with flaps popped maybe the reason the P-47 has a smaller sustained turn radius compared to the Mustang is because of the better cl/cd ratio of the Jug because of it's slotted flaps vs. the Mustang's plain flaps and the 2300hp of the Jug vs. the 1720hp of the Pony.

The only turn radius data for the Mustang I've seen posted was the figure you have that shows the Mustang turn radius compared to the Meteor, etc.  Unfortunately I've never seen any other key details of that report (e.g. config of the aircraft, alt tested, weights, engine power output etc.) that tell me what they were doing that resulted in the data for the turn radii.

Tango, XO
412th FS Braunco Mustangs


Well, we can look at thrust. Typically, the P-51D generated about 30% less thrust than the P-47D-25. However, in clean condition, the P-51D has nearly half the drag of the P-47D. Weight as tested in the game was about 8,500 lb for the Mustang and 13,500 lb for the P-47. So, the P-47 is 37% heavier. I do not see anything in the flap drag that can offset the drag and weight advantages to such a huge effect to produce the results I have shown.

Moreover, the Bf 109 also employs a plain flap, but with only a fraction of the drag shown by the P-51s. Something is rotten in the drag modeling of the Mustangs. Test data shows it getting progressively worse with each tweak of the overall drag model.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Stoney74 on August 17, 2007, 09:26:23 PM
Perhaps its not Clmax that's the issue, but the coefficient of drag.  The P-47 airfoil is basically a NACA 23012, which has a rather flat "laminar bucket", which results in a much lower Cd at a higher Cl than those associated with a 6 series, i.e. a NACA 64415 (what I thought would be a close approximation to the P-51 root shape shown in Gripen's sources).  Those airfoils have much higher Cd's than the 23XXX family at the same Cl.  So, theoretically, as the Pony turns tighter, it's Cd increases much faster than the P-47's Cd.  For example, at a Cl of 1.2, the 23012 section Cd is .012 (at Re of 3X10^6).  The 64415 has a Cd of almost .020 at the same reynolds number and Cl.  Is this significant?
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 17, 2007, 09:48:14 PM
Widewing:

Keep in mind that it's not only Cd increase but also Cl increase as well.  We know that Cl increase has the effect of reducing maneuvering velocity.  The reduction in velocity also means an increase in thrust as well.  We can see from the equation that the combination of increase in Cl, increase in thrust, and reduction of velocity all equate to smaller turn radius.

In the case of the 109, it also has leading edge slats so we can't quite compare apples to apples with the P-51 plain flaps.  Again, the case may be the differential in the change of cl/cd due to slotted flaps (P-47) and LE slats + plain flaps (109) vs. plain flaps (P-51), the resulting change in differentials in maneuvering velocities, and changing differentials in thrust give us these results for turn radius.

I readily acknowledge this is just speculation by looking at the equation vs. having data to actually crunch through the equation to check it.  Unfortunately I have no ready reference for cl/cd polars for the aircraft in question with and without flaps.

I also wholeheartedly acknowledge the degradation of turn performance of the P-51 compared to the other AH planes as you have eloquently pointed out.  However the physics suggests that it's imminently possible for the results that we have.  Thus, I can't conclude that the P-51 performance is out of line.  This is a certainly a possibility but without any other specific aircraft data to look I can't come to this conclusion.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 17, 2007, 10:12:28 PM
Stoney:

(http://brauncomustangs.org/images/turn_radius.jpg)

Yep, it would effect turn radius.  Cl/Cd is in the denominator.  The key is that turn radius is a function of all the variables above and not just cl/cd.  2ndly all those variables (except for gravity and in our case, weight) quite frankly vary!  I suppose that's why they call it aero-DYNAMICS.  We can't assume a linear relationship because of this.

That's why it could be perfectly feasible that in the case of the P-47D-25 vs. the P-51 that even though without flaps the P-47 has a worse turn radius compared to P-51 (even if the P-47's cl/cd is better as you suggest), the P-47 actually has a better turn radius with flaps popped vs. the P-51 because the differential in cl/cd between the 47 and 51 grows even larger which changes the result in turn radius.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 17, 2007, 11:37:17 PM
A quick correction:  The chief aerodynamicist for the Mustang was Ed Horkey (not Horker) that Lednicer and Gilchrist received the information from on the Mustang airfoil.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 17, 2007, 11:53:25 PM
Quote
Originally posted by dtango


In the case of the 109, it also has leading edge slats so we can't quite compare apples to apples with the P-51 plain flaps.  Again, the case may be the differential in the change of cl/cd due to slotted flaps (P-47) and LE slats + plain flaps (109) vs. plain flaps (P-51), the resulting change in differentials in maneuvering velocities, and changing differentials in thrust give us these results for turn radius.


This doesn't stand up to the fact that the slats are out when tested with flaps up. The 109 doesn't turn better than the P-51D under those circumstances. Only when flaps are lowered does the 109 gain a huge edge. Again, that makes absolutely no sense.

According to the RAF, the Mustang III out-turned a 109G with relative ease.

By the way, did you read the P-51 test reports in Gripen's links? There is no reason to assume that the P-51's drag coefficient goes up excessively approaching CLmax. It doesn't.

What I find very confusing is that in level flight, the P-51s have less drag than the 109s, even with full flaps. I test this by cutting power and timing speed loss. the 109K-4 slows much faster that the P-51D. Yet, when turning, drag rises rapidly in the P-51s and lift degrades, but not in the 109s..

You gents are trying to use formulas to confirm the flight characteristics of code... Don't waste your time. You cannot assume that the dynamics match the real aircraft as you have no idea what data is used in the model. HTC isn't talking or telling us what their parameters are. Thus, you are guessing at best.

What we do know is obtained from flight testing. I have 3 different versions of Aces High installed and all three present different test results. In each case, the P-51s have deteriorated to the current mess.

Perhaps Pyro can offer us some insight.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 18, 2007, 01:04:03 AM
Fair point about the 109 slats when flaps aren't deployed.  But it really depends on cl/cd and other values HTC has used with respect to flaps vs. not.  

On this point you've hit the nail on the head about guessing at performance.  It applies to both of us though.  Neither of us know what values HTC has used.  I'm just saying without some more definitive data to show otherwise it is just as likely that the flight model is "right" vs. "wrong" based on the math.

You mention the RAF report (reports?) on the Mustang III.  I take you absolutely seriously.  However the issue for me is without more data about how the tests were done there isn't enough information to know the relevance from these reports.  For instance, was the Mustang III running on 150 octane fuel?  Were the tests done above 20k?  Were they with flaps or no flaps?  Etc. etc.  We both know all of these could have dramatic impact on how we would intepret the reports.

If we had some wind tunnel or flight tested cl/cd polars representing flaps down conditions for the respective aircraft in question, then I think we would have something more solid to work with to do some mathematical sanity checks.

On the topic of trying to confirm the FM through the math, this is actually a soap box issue for me so please allow me to rant for sec on the topic :D!  So I don't have any notion that I can actually confirm the flight characteristics vs. the HTC flight model.  If I go down this path, in the end it becomes nothing more than a comparison of how I've chosen to model something vs. how HTC has chosen to model something.  Like you've said, a complete waste of time!  The best I can hope for is to do some overall physics sanity checks vs. some nitty gritty confirmation that the FM is 99.5% correct.

BTW, I also agree with your P-51 comment on Cd rise with Cl, but the bottom line there is that I don't think any of those drag polars are with flaps deployed.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: Stoney74 on August 18, 2007, 01:09:38 AM
Quote
Originally posted by Widewing
You gents are trying to use formulas to confirm the flight characteristics of code... Don't waste your time. You cannot assume that the dynamics match the real aircraft as you have no idea what data is used in the model. HTC isn't talking or telling us what their parameters are. Thus, you are guessing at best.


Guess I was thinking that perhaps the code HTC made samples some of these same equations to create the vectors used to move the planes around.  After that one thread where he posted pictures showing the lift vectors during the stall, I think we can safely assume that many aerodynamic characteristics of the planes are modelled using some type of math.  Otherwise the flight model wouldn't behave so realistically.  Continuing, if they keep updating the code with better equations to simulate those effects, while the data on the individual planes remain static, it could create some of the effects that degrade the P-51 performance.  I don't think they're purposely "porking" the plane.  I could be totally wrong, obviously, but regardless, its an interesting academic exercise.
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 18, 2007, 01:17:57 AM
Quote
What I find very confusing is that in level flight, the P-51s have less drag than the 109s, even with full flaps. I test this by cutting power and timing speed loss. the 109K-4 slows much faster that the P-51D. Yet, when turning, drag rises rapidly in the P-51s and lift degrades, but not in the 109s..


Sorry Wide, I missed this statement.  I hear ya.  Two things to consider:  (1) prop drag.  (2) variation of Cd with Cl (either as changing oswald efficiency or a delta_profile_drag increment with increasing Cl).

I know I know, you already have issues with the AH prop drag :D!  I'll spare us diving into the mathematical details!

I am very confident they model #2.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: bozon on August 18, 2007, 06:42:43 AM
Quote
Originally posted by Widewing
What I find very confusing is that in level flight, the P-51s have less drag than the 109s, even with full flaps. I test this by cutting power and timing speed loss. the 109K-4 slows much faster that the P-51D. Yet, when turning, drag rises rapidly in the P-51s and lift degrades, but not in the 109s..
 

This tests mostly viscous drag and windmilling prop, per mass. Induced drag is the more important at high AoA and low speeds, I think.

Quote
Something is rotten in the drag modeling of the Mustangs.

Or perhaps it is the only corrent one...
We are arguing something that I have never seen a direct test of. In no performance tests was turning ability considered with full flaps - the "maneuver" setting at best. I still seriously doubt that full flaps was that effective in any plane. The no-flaps AH FM seen about right.
Title: P-51 Airfoil and Turn Performance
Post by: Viking on August 18, 2007, 06:51:45 AM
A few anecdotes:



"BF109 was very good, very high scale fighter plane. If was superior to our Yaks in speed and vertical combat. It wasn`t 100% superiority, but still. Very dynamic plane. I`ll be honest with you, it was my dream during my war years, to have a plane like this. Fast and superior on vertical, but that didn`t happen.
Messer had one extremely positive thing, it was able to be successful fight Yak`s at 2000m and Aircobras at 6000m. This is truly unique ability and valuable. Of course, here Yak and P-39 were inferior. As far as combat on different altitudes, BF109 was universal, like La-5.
Me109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be Messer! Speedy, maneuverable,(especially in vertical) and extremely dynamic. I can`t tell about all other things, but taking under consideration what i said above, Messerschmitt was ideal for dogfight. But for some reason majority of german pilots didn`t like turn fight, till this day i don`t know why.
I don`t know what was stopping them, but it`s definitely not the plane. I know that for a fact. I remember battle of Kursk where german aces were starting "roller-coaster" rides where our heads were about to come off from rotation. No, seriously... Is it true it`s a common thing now that Messer wasn`t maneuverable?
Interviewer: Yes.
Heh.. Why would people come up with something like this... It was maneuverable...by god it was."
- Major Kozhemyako, Soviet fighter ace.


"My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away.
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."
- Robert C.Curtis, American P-51 pilot.


"Thomas L. Hayes, Jr. recalled diving after a fleeing Me-109G until both aircraft neared the sound barrier and their controls locked. Both pilots took measures to slow down, but to Hayes' astonishment, the Me-109 was the first to pull out of its dive. As he belatedly regained control of his Mustang, Hayes was grateful that the German pilot chose to quit while he was ahead and fly home instead of taking advantage of Hayes' momentary helplessness. Hayes also stated that while he saw several Fw-190s stall and even crash during dogfights, he never saw an Me-109 go out of control."
- Thomas L. Hayes, Jr., American P-51 ace, 357th Fighter Group, 8 1/2 victories


The most delightful features of the Messerschmitt were, first, in spite of its remarkably sensitive reaction to the controls, the ship showed no disposition to wander or "yaw" as we call it; neither was there any tendency to "hunt". It was a ship where the touch of a pianist would be right in keeping with the fineness of the response. And, likewise, I am sure that any ham-handed pilot who handled the controls in brutal fashion would soon be made to feel ashamed of himself.
Seldom do we find a single-seater that does not stiffen up on the controls as the ship is pushed to and beyond its top speed.
In about cruising speed, a movement of the control stick brought just exactly the reaction to be expected. And at high speed, wide open, the control sensitivity checked most satisfactorily.
Then I wanted one more check and that was at the bottom of the dive where the speed would be in excess of that ship's straightaway performance. So down we went about 2,000 feet with the air speed indicator amusing itself by adding a lot of big numbers - to a little over 400 mph. A gentle draw back on the control effected recovery from the dive; then up the other side of the hill.
- US Marine Corps major Al Williams.


"Indeed many fresh young pilots thought they were pulling very tight turns even when the slats were still closed against the wing. For us, the more experienced pilots, real maneuvering only started when the slats were out. For this reason it is possible to find pilots from that period (1940) who will tell you that the Spitfire turned better than the Bf 109. That is not true. I myself had many dogfights with Spitfires and I could always out-turn them.
One had to enter the turn correctly, then open up the engine. It was a matter of feel. When one noticed the speed becoming critical - the aircraft vibrated - one had to ease up a bit, then pull back again, so that in plan the best turn would have looked like an egg or a horizontal ellipse rather than a circle. In this way one could out-turn the Spitfire - and I shot down six of them doing it."
- Erwin Leykauf, German fighter pilot, 33 victories.


“- How did the slats behave in such a situation, did they go in and out?
 It depended on speed, if you pulled more they came out, then back in
- The slats came out completely, never half-way?
 I never came to watch them so intensely. You just knew they had come out, you could see them and feel that the lift increased pretty much."
- Antti Tani, Finnish fighter ace. 21,5 victories.


"Inexperienced pilots hesitated to turn tight, because the plane shook violently when the slats deployed. I realized, though, that because of the slats the plane's stalling characteristics were much better than in comparable Allied planes that I got to fly. Even though you may doubt it, I knew it [Bf109] could maneuver better in turnfight than LaGG, Yak or even Spitfire."
- Walter Wolfrum, German fighter ace. 137 victories.


Two P-51 shootdowns with three-cannon Messerschmitt 109 G-6/R6:
"I got both in a turning battle, out-turning them. We did several times 360 degrees until he became nervous, then pulled a little too much. His plane "warned", the pilot had to give way a little and I was able to get deflection. When I got to shoot at the other one, the entire left side was ripped off.
- So you did several full circles, you must have flown near stalling speed. Did you fly with "the seat of your pants" or kept eye on the dials? What was the optimum speed in such a situation, it was level flight?
It was level flight and flying by "the seat of your pants". What should I say, I should say I was doing 250kmh and the Mustang must have more than 300kmh. That is why I was able to hang on but did not get the deflection.
- And you was flying a three cannon plane?
Yes, but I did fly another one as mine was under maintenance. It was the experience that counted. Experience helped to decide when you had tried different things.
- In which altitude did these Mustang dogfights take place?
It must have been about 2000m."
- Kyösti Karhila, Finnish fighter ace. 32 victories.


"I cast a quick glance at the machine and then climbed up after the other enemy aircraft. Damn, he could turn! Finally I was sitting behind him. I turned so tightly that condensation trails formed behind both wingtips and my Me shuddered on the verge of a stall more than once. Fortunately, the 109 turned extremely well.
The whole air battle took place at a very low altitude. I sat behind the Russian like a shadow, and now and then I succeeded in hitting him.......
He (Russian pilot) turned sharply, leaving a heavy vapor trail, and dove away towards the northeast.......... I cut him off and closed in at high speed. My airspeed indicator was showing more than 750 km/h.
I opened fire rather too soon, but he didn't change direction, instead he put his nose down briefly so that I was suddenly a level higher than he was. I put my nose down as well, but as I was about to fire he pulled up again, and this time I ended up below him."
- Helmut Lipfert, German fighter ace. 203 victories.


The 109 should out-turn and out-fight the P-51 with ease ... because it did.
Title: P-51 Airfoil and Turn Performance
Post by: Benny Moore on August 18, 2007, 07:04:12 AM
See Rule #4, #5
Title: P-51 Airfoil and Turn Performance
Post by: Viking on August 18, 2007, 07:28:59 AM
See Rule #4
Title: P-51 Airfoil and Turn Performance
Post by: Benny Moore on August 18, 2007, 07:39:39 AM
See Rule #4, #5
Title: P-51 Airfoil and Turn Performance
Post by: Viking on August 18, 2007, 11:04:21 AM
See Rule #5
Title: P-51 Airfoil and Turn Performance
Post by: Stoney74 on August 18, 2007, 11:16:49 AM
Quote
Originally posted by Viking
The 109 should out-turn and out-fight the P-51 with ease ... because it did.


Don't know if you read the rest of this thread, but we're not even talking about P-51 versus 109 turn performance.  We're talking about the flight model of the P-51 and you're more than welcome to participate, if you have anything relevant.
Title: P-51 Airfoil and Turn Performance
Post by: Viking on August 18, 2007, 11:33:35 AM
Quote
Originally posted by Stoney74
Don't know if you read the rest of this thread, but we're not even talking about P-51 versus 109 turn performance.


Widewing's posts seem to contradict that. He constantly compares the turning circle of the P-51 with that of the 109K, and comments that it is somehow wrong. I just chimed in to say my bit on behalf of the 109. Is the flaps on the P-51 porked? I don't know; they very well might be.
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 18, 2007, 12:50:39 PM
Quote
Originally posted by Viking
Widewing's posts seem to contradict that. He constantly compares the turning circle of the P-51 with that of the 109K, and comments that it is somehow wrong. I just chimed in to say my bit on behalf of the 109. Is the flaps on the P-51 porked? I don't know; they very well might be.


I have no issues with the 109s, as many aircraft saw a boost in flaps-out turn performance with the drag update last summer. What bugs me is that the P-51s apparently don't get a proportional increase in CLmax when they use flaps, and the type of flap is very similar to that of the 109s. I used the 109K-4 as a typical example of a fighter that benefited from the drag update.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: PanzerIV on August 18, 2007, 05:43:11 PM
Although the P51s wing loading wasn't high, the wing lifting was low, thus increasing turn radius, put flaps down 1 or 2 notches and it can turn nicely.
Title: P-51 Airfoil and Turn Performance
Post by: 1K3 on August 18, 2007, 06:06:39 PM
In turning radius, I'd put P-51s in the same class as the Fw 190.  Both P-51 and Fw 190 have very good controls, but at slow speed they're pigs.
Title: P-51 Airfoil and Turn Performance
Post by: Badboy on August 18, 2007, 07:35:38 PM
Quote
Originally posted by Widewing
Have a look at this graphic and tell me if you think that a 13,457 lb P-47D-25 should out-turn a fuel light, 8,604 lb P-51B.


Here is an EM diagram for the P51D and P47D25 both with full flaps. It shows that the P51 has a better sustained turn rate, but a slightly wider radius.

(http://www.badz.pwp.blueyonder.co.uk/images/AH2 P51DvP47D25SLFLAPS.jpg)

You can see the relationship between the sustained turn radius and rate better in this diagram, which also includes the P51B.

(http://www.badz.pwp.blueyonder.co.uk/images/Various.jpg)

You can see from this that both the P51D and the P51B have higher sustained turn rates and can therefore out turn the P47D25 at full flaps when they both have 25% fuel. The P-51B has a better sustained turn rate and a smaller radius, which doesn't agree with your original graphic.

In general, a similar type of flap design can have a very different effect on wings of varying profile and planform. Their relative position, size and integration with the main wing can yield significantly different results.

Badboy
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 18, 2007, 11:51:08 PM
Quote
Originally posted by Badboy
Here is an EM diagram for the P51D and P47D25 both with full flaps. It shows that the P51 has a better sustained turn rate, but a slightly wider radius.

(http://www.badz.pwp.blueyonder.co.uk/images/AH2 P51DvP47D25SLFLAPS.jpg)

You can see the relationship between the sustained turn radius and rate better in this diagram, which also includes the P51B.

(http://www.badz.pwp.blueyonder.co.uk/images/Various.jpg)

You can see from this that both the P51D and the P51B have higher sustained turn rates and can therefore out turn the P47D25 at full flaps when they both have 25% fuel. The P-51B has a better sustained turn rate and a smaller radius, which doesn't agree with your original graphic.

In general, a similar type of flap design can have a very different effect on wings of varying profile and planform. Their relative position, size and integration with the main wing can yield significantly different results.

Badboy


Well, your diagrams are completely dependent upon the data used to plot them. I get substantially different turn radius figures for many of the aircraft on the diagrams. You have the F6F-5 at nearly a 500 foot radius. Depending upon how hard I push it, I get between 457 and 462 feet (the latter can be sustained forever without a twitch). Meanwhile, the F6F is turning at nearly 2 degrees per second faster than the F4U-1D (21.2 deg/sec vs 19.4 deg/sec).
Likewise, I can get 593.8 feet for the P-51D (compared to Mosq's 632.9 ft) at 18.12 deg/sec (compared to Mosq's 16.3 deg/sec).

My diagrams come directly from film.. They show the best turn radius I could generate. If it differs with your data, then I would retest the aircraft and verify that the data is the best available.

Finding the smallest turn radius often means not flying the fighter TOO deep into the stall buffet. To do so increases the diameter of the circle and increases the time required to complete a circle. It takes several attempts to find the required balance. Sometimes, more than several.

Now here's where the P-51s get strange. I tested the D model at all flaps settings and the rate of turn varies very little, but the radius does tighten.

Here's the data, by flap position, time, mph and degrees/second to complete 3 turns.

No flaps: 60.12 seconds @ 174 mph 17.96 deg/sec
1/5: 59.78 seconds @ 171 mph 18.066 deg/sec
2/5: 59.76 seconds @ 155 mph 18.072 deg/sec
3/5: 59.81 seconds @ 146 mph 18.057 deg/sec
4/5: 59.94 seconds @ 137 mph 18.02 deg/sec
Full Flaps: 59.59 seconds @ 128 mph 18.12 deg/sec

Essentially, regardless of speed or flap position, the rate of turn is stagnant. That is, to my eye, is rather unusual. I'd sure like to see an explanation of the P-51's flight modeling, because I don't understand why it has deteriorated, nor do I understand the constant turn rate regardless of flap position.

Also, here's the diagrams of the F6F-5 and F4U-1D.

(http://home.att.net/~c.c.jordan/F6F-F4U-1D-Turn-Radius.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: TequilaChaser on August 19, 2007, 06:35:52 AM
Widewing,
look at the 2nd diagram, he states it is from AH2 version 2.08 patch 3 thru AH2 version 2.10 patch 2..

that is probably why you both have differences....

Badboy uses his own test results I thought?   the planes were done in all different version/patches  is what I would assume he meant by posting that on his diagram...and with the tweaking done to the drag model or whatever some claim ( trying to stay non biased ;)  ) then thaere would be the difference.....you testing this week, his test results are over a span of version updates....

how it reads anyhow......


I really like your new idea of showing from the film, Widewing, it also shows how far in the turn one can roll the lift vector( angle of wings ) and can compare them as well...... with the red line ladder trails being very close ( thin ) or far apart ( wide ).......

~S~
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 19, 2007, 11:02:13 AM
Here's the diagrams for both P-51s. I managed a 589.0 foot radius for the P-51B, but similar to the P-51D, it required 7 separate tests to get the best number. Turn rate is inferior to the more powerful P-51D. Moreover, like the P-51D, the turn rate with no flaps (16.58 deg/sec) is very close to full flap turn rate (16.65 deg/sec). In comparison, the F6F-5 generates a turn rate of 19.39 deg/sec with no flaps and 21.02 deg/sec with full flaps.

As I said before, it appears that the P-51s see no increase in turn rate using full flaps vs no flaps. The net gain in turn rate is just 0.07 degrees per second (well within any margin of test error), whereas the F6F-5 sees an increase of 1.63 degrees per second.

Unless someone can show me some actual test data that establishes that the real P-51s didn't get an increase in turn rate with flap use, I tend to believe the P-51 flight model is incorrect.

(http://home.att.net/~c.c.jordan/P-51s-Turn.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Badboy on August 19, 2007, 01:05:26 PM
Quote
Originally posted by Widewing
Well, your diagrams are completely dependent upon the data used to plot them. I get substantially different turn radius figures for many of the aircraft on the diagrams.

That's true, and I think I can explain that if we back up a bit to something you said earlier:

Quote
Have a look at this graphic and tell me if you think that a 13,457 lb P-47D-25 should out-turn a fuel light, 8,604 lb P-51B.

I looked at the diagram you posted with that text, and it is difficult to draw conclusions from it, other than the overhead shot of the P-51D and the P47D25 film flight path trails look very similar, with perhaps a slightly better turn rate for the P51D.

Your point about variations in data is a good one, and I can also get both the P51D and the P47D25, along with most of the other aircraft to fly a slightly tighter turn radius, but that isn't necessarily the right thing to do. Take a look at this diagram.

(http://www.badz.pwp.blueyonder.co.uk/images/Various2.jpg)

It shows that both aircraft can be flown slightly deeper into the stall, resulting in a slightly lower speed, a slightly smaller turn radius and in both cases a slightly lower sustained turn rate, which is an indication of below maximum performance. The curves shown in the diagram above are for the current version, and they show that the P51D does indeed out turn the P-47D25, which I think would agree with your expectation.

The only caveat being this, the P47D25 has a couple of advantages, if you take another look at this EM diagram:

(http://www.badz.pwp.blueyonder.co.uk/images/AH2 P51DvP47D25SLFLAPS.jpg)

You notice that the P47D25 has a higher instantaneous turn rate and bleeds speed more quickly, which means the P47D25 pilot is almost always going to be able to tighten his turn more, and more quickly than the P51D pilot which will mean that the P51D pilot will find it very difficult to avoid conceding the first shot. The P51D's advantage is an endgame advantage that would suit energy fighters better, which is good because in this match up the P51D should clearly be flown as the energy fighter, despite having the better maximum sustained turn rate.  

Quote

Now here's where the P-51s get strange. I tested the D model at all flaps settings and the rate of turn varies very little, but the radius does tighten.

Here's the data, by flap position, time, mph and degrees/second to complete 3 turns.

No flaps: 60.12 seconds @ 174 mph 17.96 deg/sec
1/5: 59.78 seconds @ 171 mph 18.066 deg/sec
2/5: 59.76 seconds @ 155 mph 18.072 deg/sec
3/5: 59.81 seconds @ 146 mph 18.057 deg/sec
4/5: 59.94 seconds @ 137 mph 18.02 deg/sec
Full Flaps: 59.59 seconds @ 128 mph 18.12 deg/sec

Essentially, regardless of speed or flap position, the rate of turn is stagnant.


Ok, I've used your data to plot the radius and rate curves shown below:

(http://www.badz.pwp.blueyonder.co.uk/images/WWP51DFlaps.jpg)

It shows that for the P51D the turn radius decreases as you lower the flaps, while the sustained turn rate remains fairly constant. It means that the optimal situation is with full flaps because that's where it has the best radius and rate, so once you start dropping flaps on the P51D, you start to fall into a trap, you need to keep lowering more flaps to max perform the aircraft, which is contrary to the way the P51D should really be flown.

But it doesn't work that way for every aircraft. Here is a similar example for the F4U1D:

(http://www.badz.pwp.blueyonder.co.uk/images/BBF4U1DFlaps.jpg)  

It shows that for this aircraft the optimum situation occurs when 2 notches of flaps have been lowered. Lowering more than two notches will reduce the turn radius, but it will also degrade the sustained turn rate, which is not good. A player who uses full flaps on the F4U1D against one who only uses 2 notches will make early gains, and may even tighten his turn enough for a snap shot, but if he doesn't make the shot, he will soon be wallowing with low E, possibly trying to pull his nose over for additional shots with high yo-yos while the guy at 2 notches will either be able to keep his nose high and out turn him or when he has sufficient altitude advantage, just use the turning room provided by the vertical separation to turn under for the kill. The point being that trying to use only 2 notches of flaps when ever possible in the F4U1D, and thus optimising sustained turn rate, is good.

Quote
That is, to my eye, is rather unusual. I'd sure like to see an explanation of the P-51's flight modeling, because I don't understand why it has deteriorated, nor do I understand the constant turn rate regardless of flap position.


Ok, those are two good points, one regarding the sustained turn rates, the other the changes in the flight model.

Firstly, issues around sustained turn rates and radii are always very perplexing, because the cause and effect relationships are not always intuitive and the mathematics required to resolve such questions is fairly complex with an enormous number of factors interacting with each other. I have the advantage of a flight model that I can tweak in order to see the effect of almost any change. The results can be surprising, but changes resulting from different wing and flaps configurations can reproduce everything we see in Aces High... Which leads me to your second point.

We have seen a lot of changes in the game over the years, some more dramatic than others, and during that time there have always been players who either dislike or disagree with the direction of that change. Those issues almost always arise because of comparisons with real life. But as we have so often seen, with the sparse and varied sources available we can't pin down the real aircraft behaviour with any degree of certainty. Trying to keep the errors as small as possible is as good as it gets, and everything I've seen points to the fact that HTC are constantly striving in that direction. How close they come to getting it right will always be a matter for speculation on these boards, but if you are a player trying to do well in the game, that is only a distraction.

Of course, a lot of folk enjoy that sort of discussion, but I don't have any real interest in how close the aircraft might be to the real thing, other than to help clarify when there is some doubt about the way the flight model is behaving. At the moment, I don't see anything that should cause any concern.    If you want to excel in Aces High, it doesn't matter how the P-51D has changed between patches, all that really matters is how it compares to the other aircraft right now! My only motivation is to provide information to help players do better in the game.

Badboy
Title: P-51 Airfoil and Turn Performance
Post by: Charge on August 20, 2007, 03:24:35 PM
I'd say that what ever you calculate might give you any kind of different results but for as long as none of those formulas can take into account the wing profile's effect on turning you are bound to get only very general idea of turning performance. More specifically I mean that in slow speed the performance of near symmetric profile is different from, say, NACA 2300 series and if the symmetric profile is optimized for laminar flow with the camber being quite rear in the profile the slow speed performance will suffer.

-C+
Title: P-51 Airfoil and Turn Performance
Post by: SteveBailey on August 22, 2007, 04:30:57 AM
Quote
the P-51D has changed between patches, all that really matters is how it compares to the other aircraft right now!


Copmared to other lw rides,.  it's a pig
Title: P-51 Airfoil and Turn Performance
Post by: Wmaker on August 25, 2007, 08:05:17 AM
Quote
Originally posted by Widewing
According to the RAF, the Mustang III out-turned a 109G with relative ease.


The 109G tested against Mustang was a nightfighter with wing cannons installed.
Title: P-51 Airfoil and Turn Performance
Post by: Badboy on August 29, 2007, 06:22:19 PM
Quote
Originally posted by Widewing
Now here's where the P-51s get strange. I tested the D model at all flaps settings and the rate of turn varies very little, but the radius does tighten.

Missed this point earlier, and should add that this isn't strange at all.

If you only consider two variables influenced by the flaps, the increase in coefficient of lift, and the increase in drag, that outcome is predictable.

It works like this, increasing the coefficient of lift results in the tighter turn radius you are seeing. However, the turn rate can be affected in a variety of ways depending on the drag resulting from the use of flaps. For example, a fairly small increase in drag may result in an increase in sustained turn rate, but a higher drag penalty will result in a lower sustained turn rate, so a medium drag increase will result in the sustained turn rate staying about the same. That is what you are seeing, and in different aircraft we see all three outcomes.

If you take simple equations for sustained turn rate and radius, and plug in typical values for the P51, it is possible to see exactly that.

If you would like to see the math let me know.

Badboy
Title: P-51 Airfoil and Turn Performance
Post by: Tilt on August 30, 2007, 07:16:22 AM
Quote
Originally posted by Widewing

No flaps: 60.12 seconds @ 174 mph 17.96 deg/sec
1/5: 59.78 seconds @ 171 mph 18.066 deg/sec
2/5: 59.76 seconds @ 155 mph 18.072 deg/sec
3/5: 59.81 seconds @ 146 mph 18.057 deg/sec
4/5: 59.94 seconds @ 137 mph 18.02 deg/sec
Full Flaps: 59.59 seconds @ 128 mph 18.12 deg/sec

Essentially, regardless of speed or flap position, the rate of turn is stagnant.  


If the proposal here is to challenge the P51 drag modeling with flaps at various settings would it not also show up (i.e see symptoms of the same) when looking at rate of climb figures?

If you set auto speed (IAS) to the figures above what roc at what TAS is returned at the various flap settings? How does it compare with the 109 and P47 also tested for comparison?

Seems that roc can be tested with far less potential error and used to corroburate the turn data you find without having to discount variations in bank angle, rudder input, and nose attitude that may be exprienced across flap settings and across ac types under test.
Title: P-51 Airfoil and Turn Performance
Post by: dtango on August 30, 2007, 10:13:46 PM
Quote
Originally posted by Tilt
If the proposal here is to challenge the P51 drag modeling with flaps at various settings would it not also show up (i.e see symptoms of the same) when looking at rate of climb figures?


No it wouldn't Tilt.  Climbs and turns --- apples and oranges.  There was a thread in the near past that went on for over 10 pages  where I tried to explain why.  I really hope we don't have to go through that again :)!

The simplest I can put it is that excess power depends on load-factor (squared), airspeed, altitude, and e (oswald efficiency). Ignoring altitude, the values of these variables are not the same between a steady climb vs. a sustained turn.

Tango, XO
412th FS Braunco Mustangs
Title: P-51 Airfoil and Turn Performance
Post by: Tilt on August 31, 2007, 03:18:15 AM
:)  thanks for the reply............. I must admit ignorance on the matter but can see how much more complex turn is..............

It just seemed to me that there was a focus forming around drag modelling (of flaps and their effects in particular) and whilst the sum of combined effects are different between climb and turn, drag influences both . (more easily measurable in climb tests)

It seemed to me that if the roc model does not show any idiosyncrasies attributable to drag then another factor was being brought into play to produce idiosyncrasies under turn................ and if Widewings observations are correct, these other idiosyncrasies are particular to the P51 model.

How would HTC model a laminar (or more laminar like) flow wings  lift  responce to increased G and by how much would CL change when its split flaps are deployed under G and how would this differ to ac with more conventional wings?
Title: P-51 Airfoil and Turn Performance
Post by: Charge on August 31, 2007, 06:42:54 AM
i think P51 has plain flaps, not split and what I'm interested of is the Cl behavior of its wing with different R numbers. It may turn very well in high and moderate air speeds but when AoA increases and air speed drops the wing may suddenly lose a lot of its lift if the profile does not support the low pressure in front of wing. But when does this actually happen?

The P51 may indeed be one of the most troublesome a/c to model trying to get its flight characteristics right in relation to a/cs with more conventional wing designs.

-C+
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 31, 2007, 07:59:34 AM
Quote
Originally posted by Charge
i think P51 has plain flaps, not split and what I'm interested of is the Cl behavior of its wing with different R numbers. It may turn very well in high and moderate air speeds but when AoA increases and air speed drops the wing may suddenly lose a lot of its lift if the profile does not support the low pressure in front of wing. But when does this actually happen?

The P51 may indeed be one of the most troublesome a/c to model trying to get its flight characteristics right in relation to a/cs with more conventional wing designs.

-C+


According to NACA, the P-51 (in this case, a P-51B) has slotted flaps.. See image below.

(http://home.att.net/~c.c.jordan/NACA829.jpg)

Likewise, NACA Report 1044 and 829 show that there was nothing unusual about the way the P-51 wing performed at all airspeeds. It was among the very best in terms of CLmax, in service condition. It also demonstrated that its CLmax increased between Mach .45 and Mach .58, whereas conventional airfoils always suffered decreased CLmax as speed increased.

Both reports can be located via a Google search.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Charge on August 31, 2007, 10:33:47 AM
Thanks for doc numbers WW.

According to 829 the maximum Cl the P51B could achieve was 1.4. The Corsair with its 2300 series wing exceeded 1.6. Page 615 shows some comparison too between different wings although it is about different gun apertures and fairings.

Page 599 "the stall characteristics are probably good" Ok, probably...

I think the description says it quite well "compromise, low drag".

-C+
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on August 31, 2007, 02:26:16 PM
Quote
Originally posted by Charge
Thanks for doc numbers WW.

According to 829 the maximum Cl the P51B could achieve was 1.4. The Corsair with its 2300 series wing exceeded 1.6. Page 615 shows some comparison too between different wings although it is about different gun apertures and fairings.

Page 599 "the stall characteristics are probably good" Ok, probably...

I think the description says it quite well "compromise, low drag".

-C+


If we compare the data for the P-51B and F4U-1 in "service condition" (which means as it will be flown in combat units), the P-51B comes in with a CLmax of 1.40, whereas the F4U-1 can do no better than 1.17 without taping and fairing. These tests were done with the props removed, to measure the CLmax characteristics of the wings independent of being blown by the propellers. The F4U wing leaks air from underside to top side. However, the P-51 does not, being a much cleaner and smoother surface without wing fold joints and a cleaner transition from wing to fuselage.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Stoney74 on August 31, 2007, 07:05:32 PM
Quote
Originally posted by Widewing
...and a cleaner transition from wing to fuselage.


I always thought the gull-wing configuration lowered the interference drag created by the wing to fuselage joint, when compared to a conventional, low-wing aircraft...
Title: P-51 Airfoil and Turn Performance
Post by: Charge on September 01, 2007, 08:53:33 AM
BTW what was the effect of the forward joint extension in D model? IIRC it was deleted in later models.

"The F4U wing leaks air from underside to top side."

The effect of that is also measured in the same document and the effect seems to be quite minimal according to figure on page 610. The low Cl is puzzling. On page 606 the Cl figure is again different.

It must be noted though that the speeds where measurements were done were quite small as they were below 100mph (60mph). Their loaded performance in higher speed is probably somewhat different.

What ever the profile performance is that is only one variable in the equation although a significant one when trying to figure the performance at the edge of the flight envelope. It seems that although both P51 and FW190 had a twist i.e. washout in wing they both suffer from somewhat sudden loss of control and the twist does not seem to do what it is supposed to which is to provide delay and warn of stall -or maybe the stall actually is less abrupt than it would be without the twist. What 190 wing behaves like that is a mystery to me since it uses a more conventional airfoil.

I think this table gives some idea of the relative behavior of wing sections.
(http://www.lv36.org\kuvat\AD_pg106.jpg)

Source: Abbott&Doenhoff 1949 "Theory of Wing Sections"

-C+

PS. Bah, it doesn't show....
Title: P-51 Airfoil and Turn Performance
Post by: Neil Stirling on September 02, 2007, 05:07:10 AM
The 109G tested against Mustang was a nightfighter with wing cannons installed.

109 G-2 R N.228 used in the trials was not fitted with under wing cannon.  

http://www.wwiiaircraftperformance.org/mustang/mustang-tactical.html

http://www.acompletewasteofspace.com/modules.php?name=Forums&file=viewtopic&t=10048&start=30

Neil.
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on September 02, 2007, 08:44:25 AM
Quote
Originally posted by Neil Stirling
The 109G tested against Mustang was a nightfighter with wing cannons installed.

109 G-2 R N.228 used in the trials was not fitted with under wing cannon.  

http://www.wwiiaircraftperformance.org/mustang/mustang-tactical.html

http://www.acompletewasteofspace.com/modules.php?name=Forums&file=viewtopic&t=10048&start=30

Neil.


Here's the photo of the 109G in question, as shown in the second link...

(http://img.photobucket.com/albums/v11/brentce/RN228.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on September 02, 2007, 12:30:02 PM
I performed some additional turn tests, comparing several aircraft.

Tested were: P-51B, Bf 109G-2, Fw 190A-5, Tempest Mk.V, La-5FN and the Ki-61.

I have been advocating the the P-51's turn radius is larger than it should be and that its turn rate shows not increase when using flaps.

Likewise, I believe that Ki-61 suffered greatly from the last tweak to the drag model. Testing shows that the Ki-61 has a rather large turn radius compared to the others tested, while having the lowest wing loading (substantially) and just about the highest CLmax. When tested by TAIC in 1944, the Ki-61 proved to have a minimum turn radius equal to the FM-2 (source) (http://www.wwiiaircraftperformance.org/japan/Tony-I.pdf).

Thus, the Ki-61 should have the smallest turning circle by a significant margin.. It doesn't.

Here's a turning circle comparison taken directly from film, with each aircraft flown to its limit of controllability. Weights and wing loading data is provided as well a bar graph showing relative diameters of turn circles. Draw your own conclusions.

(http://home.att.net/~c.c.jordan/MinTurn.jpg)

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 02, 2007, 01:55:05 PM
Well Widewing, to me the P-51 and 109 looks relatively correct. They have about equal wing loading, but the P-51 has a wing profile that is inefficient at high AoA while the 109 got better power loading and has slats. The P-51 might even turn a bit too good compared to the 109G-2. As for the other aircraft I agree that the Ki seems to turn worse than it should, but in this game engine power/prop wash seems to have a great deal of effect on lift.
Title: P-51 Airfoil and Turn Performance
Post by: Anyone on September 03, 2007, 05:21:51 AM
i aint no good with numbers or figures like you guys and reading some of these well done graphs etc is great but.....

maybe the P51 of old was wrong and the current one is right?



the P51 wasnt the greatest low-med alt dogfighter, it was a high alt escort plane, it was designed for long runs to berlin and back, nothing more really.

P51's only really won dogfights because there was so many of em, plus better training on fighting tactics, something that was starting to lack in German pilots by the end.

but in game, everyone (err mostly) knows there planes inside out, so its good pilots getting the most out of there planes, hence the P51 in a 1on1 will not be that great. if it was a 3to5 on 1  (p51 vs 109) then the results would match real life?



i know this a rubbish point to put forward without figures etc but its just the way i see it.
Title: P-51 Airfoil and Turn Performance
Post by: TDeacon on September 03, 2007, 10:45:02 AM
"maybe the P51 of old was wrong and the current one is right?"

It is not ideal when the relative behavior of an Aces High aircraft changes significantly, apparently by accident.  Any such change implies an inadvertent programming or modeling error, which should be fixed.  Ideally, any significant changes should be intentional, and justified by presumably new data.  So, if the old P51 was "wrong", why has it changed, and where is the new data?
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on September 03, 2007, 01:40:49 PM
Quote
Originally posted by Viking
Well Widewing, to me the P-51 and 109 looks relatively correct. They have about equal wing loading, but the P-51 has a wing profile that is inefficient at high AoA while the 109 got better power loading and has slats.


NACA 829 demonstrates that the P-51's wing was not inefficient at high AoA.

See the chart below.

(http://home.att.net/~c.c.jordan/P-51-CLmax.jpg)

It sure looks like the P-51B wing is more efficient at high angles of attack than either the F4U-1 or the P-63A.

NACA 1044 shows that the P-51B's CLmax at Mach .25 was the same as the P-38.

Then we have the RAF tests of relative turning ability against the Bf 109G-2, that conclude, "The Mustang III is greatly superior." Even tested with a pair of full drop tanks against the 109G-2 and the Fw 190A, the RAF concluded: "The tanks do not make quite so much difference as one might expect. The Mustang III can at least turn as tightly as the FW.190 (BMW.801D) without stalling out and therefore definitely more tightly than the Me.109G."

Neil Sterling provides a link to the test report in his post a few above this one.

According to RAF tests of the Mustang III, it should out-turn the 109G-2 and the 190A (an A-3?). Both the P-51 and Fw 190 seem to suffer from excessively large turn radii in AH2. I don't know why, but this is at odds with the available test data.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 03, 2007, 03:02:26 PM
Quote
Originally posted by Widewing
NACA 829 demonstrates that the P-51's wing was not inefficient at high AoA.

See the chart below.

(http://home.att.net/~c.c.jordan/P-51-CLmax.jpg)

It sure looks like the P-51B wing is more efficient at high angles of attack than either the F4U-1 or the P-63A.





That is because you don’t consider drag in your comparison. A laminar flow wing produces less drag at low AoA than a more conventional WWII airfoil, but this comes at the cost of more drag for the same Cl at high AoA.




(http://www.dreesecode.com/primer/p5_f002.jpg)

(http://www.dreesecode.com/primer/p5_f003.jpg)



So compared to a plane with a typical WWII airfoil the P-51’s wing would produce similar lift at high AoA, but at a higher drag penalty. Given that the P-51 already suffers from a lower power to weight ratio than the 109G this clearly puts the P-51 at a disadvantage in stall turning. Especially given…



(http://history.nasa.gov/SP-367/fig63.jpg)



… the 109’s slats which effectively increases the maximum AoA of its wing, allowing it to produce more lift at low speeds without stalling.






Quote
Originally posted by Widewing
The Mustang III can at least turn as tightly as the FW.190 (BMW.801D) without stalling out and therefore definitely more tightly than the Me.109G.


Must have been a Kanonenboot 109 (gondola guns), because the 109G definitively has a tighter turning circle than the 190A. If not those comments simply does not make sense at all.
Title: P-51 Airfoil and Turn Performance
Post by: TUXC on September 03, 2007, 03:12:17 PM
Doesn't it seem a little fishy that the British tests indicate that the 190 turns better than the 109 when experienced 109 pilots and the Russians both recognized its abilities in a turn fight? There's a quote somewhere from a Russian ace saying the he was surprised the 109s wouldn't turnfight more often since they could turn very well.

http://www.wwiiaircraftperformance.org/mustang/mustang-tactical.html

Turning circle (Mustang III vs. Fw190A)
42.            Again there is not much to choose. The Mustang is slightly better. When evading an enemy aircraft with a steep turn, a pilot will always out-turn the attacking aircraft initially because of the difference in speeds. It is therefore still a worthwhile maneuver with the Mustang III when attacked.

Turning Circle (Mustang III vs. Bf 109G
49.            The Mustang III is greatly superior.



http://www.wwiiaircraftperformance.org/tempest/tempestafdu.html

Turning Circle
47. The Tempest is slightly better, the Me.109G being embarrassed by its slots opening near the stall.

Experienced German and Finnish 109 pilots said that the slats helped with turning, but could cause an inexperienced pilot to back off when they deployed.

This is a good collection of quotes by pilots who scored several kills in the 109:
http://www.virtualpilots.fi/feature/articles/109myths/

Specifically:
http://www.virtualpilots.fi/feature/articles/109myths/#whyhard
http://www.virtualpilots.fi/feature/articles/109myths/#slats
Title: P-51 Airfoil and Turn Performance
Post by: Badboy on September 03, 2007, 03:12:36 PM
Quote
Originally posted by Widewing
Testing shows that the Ki-61 has a rather large turn radius compared to the others tested, while having the lowest wing loading (substantially) and just about the highest CLmax.

Just a word of warning here for the unwary with regard to aircraft parametric data. It is true that a low wing loading and a high Clmax are generally good when it comes to turning, but you can't draw conclusions about sustained turns based on those factors alone as safely as you can for instantaneous turns.

The reason is that it is possible for one aircraft to have a lower wing loading and a higher Clmax than another, yet still have a larger sustained turn radius and lower sustained turn rate.

The reason is due to the other variables involved. I can explain it easier with an example

Consider two aircraft, the first we will call aircraft A has a wing loading of 34 lb/ft^2 and a Clmax of 1.7 while the other we will call aircraft B has a wing loading of 36lbs/ft^2 and a Clmax of 1.6, which one would you expect to have the tighter sustained turn radius?

Well, aircraft A has a lower wing loading and a higher Clmax so you might expect it to have the smaller sustained turn radius.

Do you agree?  If so, for this example, you would be wrong!!

In general it all depends on the variables that have not been considered.

In the example above you would probably be even more surprised if I told you that aircraft B was 1000lb heavier than aircraft A, with a lower Clmax and yet it still has a tighter sustained turn radius and a higher sustained turn rate.

Surprised?  Good, then I have your attention. So what have we left out that makes so much difference?

Well we haven't considered the power plant or prop. The combination of a more powerful engine and more efficient prop can result in a higher sustained turn speed, which will increase the sustainable g, thus reducing the sustained turn radius and increasing the sustained turn rate.

We also haven't really considered the the entire wing geometry, only the area. If we begin to introduce other factors, such as the aspect ratio of the wing we will see that a higher aspect ratio will have a tendency to reduce the induced drag, thus increasing the sustained turn speed, which in turn will increased the sustained g which will reduce the sustained turn radius.

In the example I quoted above, I gave aircraft B (remember it was heavier, and had a higher wing loading and lower Clmax) a more powerful engine, a higher aspect ratio wing and a more efficient prop and it not only had a smaller turn radius, it had a much higher sustained turn rate. Contrary to the conclusion that would most likely be jumped to.

The important thing to remember here is that while wing loading, Clmax and power loading alone can give some indication of relative performance, it can do so only if all other factors are considered equal, when you consider dissimilar aircraft, the other factors are rarely equal, and if they vary considerably conclusions reached on limited data, such as wing loading and Clmax alone can be unsafe, so it is always wise to exercise some caution.

If in doubt, it is always better to use as much data as possible, and carry out a more detailed analysis, rule of thumb estimates aren't a good basis for making predictions about dissimilar aircraft performance.

Hope that helps.

Badboy
Title: P-51 Airfoil and Turn Performance
Post by: Charge on September 04, 2007, 05:13:28 AM
"The Mustang is always out-turned by the Spitfire IX." Nothing new.

"Use of flaps on the Mustang does not appear to improve the turning circle." :huh I find it hard to believe that.

"There is adequate warning of the high-speed stall in the form of elevator buffeting, followed by tail buffeting." This is concluded in NACA report as well concerning the use of flaps in turns as the flap turbulence giving warning of the  stall before it actually happens.

As mentioned already according to the firs doc Neil posted the FW190 presumably out-turned the 109 and that was considered more or less normal. That is strange but depends on the speed. There is an anecdotal story in which a Spit driver is being out-turned by a 190 and I suspect that happened in relatively high speed. The high speed turn performance of 190 in AH is nothing phenomenal and it is certaainly worse than that of Spit or 109 and it is arguable if it should lose speed that rapidly, but that is another story.

It is interesting that 109 is considered as good in zoom climb as Mustang. I have always thought that Mustang should be better due to greater weight and thus greater inertia.

-C+
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 04, 2007, 07:51:49 AM
"Use of flaps on the Mustang does not appear to improve the turning circle..."

Shoot ... there goes Widewing's entire argument on Pony-flaps. Seems the P-51's flaps are modeled correctly after all.
Title: P-51 Airfoil and Turn Performance
Post by: Charge on September 04, 2007, 08:22:47 AM
Not really. I find it hard to believe in many of the observations in these documents. Many times they are just opinions and quite subjective observations. The flap deployment effect simply cannot be ineffective but at certain very narrow speed range near total stall -if even then. There are no results for completing 360deg turns or such even remotely "hard evidence" -merely opinions.

-C+
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 04, 2007, 09:58:20 AM
There are such "hard evidence" for other aircraft such as the Spitfire with regard to turning circle with and without flaps. Why not for the Pony?
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 04, 2007, 10:34:18 AM
Messerschmitt Bf 109 G-6/U2 (TP814 c/n 412951) RAF

(http://1000aircraftphotos.com/Contributions/Gladwin-Simms/3600L.jpg)

This Bf109G-6/U2 was used for tactical trials by the Air Fighter Development Squadron until crashing on take-off in November 1944. It is as you might have noticed a Kanonenboot, and its performance fits very nicely with the aforementioned P-51B vs. 109G test results:

http://www.wwiiaircraftperformance.org/mustang/mustang-tactical.html

Quote
Maximum Speed
45.            The Mustang III is faster at all heights. Its best heights, by comparison, are below 16,000ft (30mph faster approx) and above 25,000ft (30mph increasing to 50mph at 30,000ft).


Not surprisingly the Pony is faster than the G-6/U2 at all altitudes.


Quote
Maximum climb
46.            This is rather similar. The Mustang is very slightly better above 25,000ft but worse below 20,000ft.


The added weight of the extra guns and ammo reduces the 109G-6/U2’s climb rate to about parity with the Pony.


Quote
Zoom Climb
47.            Unfortunately the Me. 109G appears to have a very good high-speed climb, making the aircraft very similar in a zoom climb.


The added weight of the extra guns and ammo makes the G-6/U2 similar to the Pony in zoom climb.


Quote
Dive
48.            On the other hand in defense the Mustang can still increase the range in a prolonged dive.


The added drag of the extra guns increases the Pony’s high speed advantage in shallow dives.


Quote
Turning Circle
49.            The Mustang III is greatly superior.


The added weight of the extra guns and ammo gives the 109 a worse wing loading than the Pony.


Quote
Rate of Roll
50.            Not much to choose. In defense (in a tight spot) a rapid change of direction will throw the Me.109G’s sight off. This is because the 109G’s maximum roll is embarrassing (slots keep opening)


This was a bit surprising. :)  The Pony has always had a better roll rate than the 109 in AH.


This 109G-6/U2 also fits with the earlier comparison with the 109A. A heavy Kanonenboot 109 would turn worse than a light 190A.
Title: P-51 Airfoil and Turn Performance
Post by: Neil Stirling on September 04, 2007, 11:32:32 AM
Army Air Force Wright Field report on EB-102 Bf 109G-6/trop Wnr 16416.

http://www.wwiiaircraftperformance.org/me109/matcom109g.html

No underwing cannon on this one either. Visit LEMB for confirmation.

I wonder if the speed used when turning may explain some of the differences?

Neil.
Title: P-51 Airfoil and Turn Performance
Post by: MiloMorai on September 04, 2007, 12:08:10 PM
Quote
The added drag of the extra guns increases the Pony’s high speed advantage in shallow dives.

Kurfurst says the drag was negligable, something like ~10kph speed loss with the gondies. It should also be mentioned the drop tank mounts of the P-51 had more drag than the 109.

Check his site, for am sure the correct number is there.

This Messerschmitt Bf-109G-6/U2, W.nr.412951, White 16 of I/JG1, landed by mistake at Manston in the early hours of 21 July 1944. It was flown to the RAE and became TP814.

It is doubtful this is the a/c used in the P-51 trials since it is dated Dec 1943. Now in Neil's link, most likely.
Title: P-51 Airfoil and Turn Performance
Post by: Neil Stirling on September 04, 2007, 01:43:03 PM
It is doubtful this is the a/c used in the P-51 trials since it is dated Dec 1943. Now in Neil's link, most likely

Milo  is correct the above aircraft is TP 814 the serial number can be seen just fwd of the empenage. The aircraft used in the original test was R.N 228. Note the date of the stamp, 8th May 1944. And as Milo said,TP 814
did not arrive in the UK until the 21st of July 1944.
 


(http://hometown.aol.co.uk/JStirlingBomber/RN.228.jpg)


Neil.
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 04, 2007, 01:55:05 PM
Perhaps allied pilots just don't know how to fly a 109 then. ;)
Title: P-51 Airfoil and Turn Performance
Post by: MiloMorai on September 04, 2007, 02:00:00 PM
Quote
Originally posted by Viking
Perhaps allied pilots just don't know how to fly a 109 then. ;)

At that time how many LW pilots knew how to fly a 109? Allied pilots certainly had more flight time, especially those doing flight testing.
Title: P-51 Airfoil and Turn Performance
Post by: Viking on September 04, 2007, 02:06:50 PM
At that time? Only the few Experten still alive.
Title: P-51 Airfoil and Turn Performance
Post by: Widewing on September 04, 2007, 08:42:58 PM
Inasmuch as there is much disagreement among posters and somewhat controversial comments in test reports, I figured it was time to talk to probably the best source alive on the P-51 Mustang.

Dudley Henriques is a pal of mine, of sorts. We have known each other for about 11 years. Our discussions are always centered on aircraft. Dudley has about 4,000 hours of flight time in P-51s. He is a long-time air show performer flying aerobatic displays. Dudley is a past President of the International Fighter Pilots Fellowship. He has served as Eastern Region Director, and Director of Special Projects, for the Combat Pilots Association of the United States. He was an active member of the Professional Race Pilots Association, and the P-51 Mustang Pilots Association. For health reasons, Dudley quit competitive flying about 12 years ago. Dudley has flown just about every fighter in the inventory, from Mustangs through the F-14A and the YF-17.

Through Dudley, I was introduced to John Callahan. John flew the P-51B in the ETO and later the P-51K in the PTO. John was asked about flap use in combat.

First, here's what Dudley had to say....

"I always found the best Vc for the 51 was at about 270 indicated. This married to about +8g's gave me a maximum TR and was for me at least the best corner velocity for the Mustang.

Considering a Vc of 270mph with no flaps, and that up to 20 degrees of flap could be used in the bird up to 400 indicated, all other flap speeds are below corner up to 50 degrees at 165 indicated which is fine....BUT!!!! At 270 pulling about +8g on the pole is already giving you best rate.

My guess is that unless you are turning at max rate and radius and need less radius for a tracking solution, I would leave the flaps alone. Using them will decrease your turn radius but at a HUGE payout of bleeding Ps like a stuck pig. Any advantage I would imagine would be temporary at best and downright destructive to your energy state to say the least.

Just my 2 cents on all this from hassling around with Bearcats, Spits, and assorted other play toys for big boys :-)) .. "

John tosses in his thoughts:

"The two combat areas fought the bird differently. In Pacific the Jap birds could out turn us and had a higher perch so we kept the airspeed up and hit and ran, climbing back to a top position in a high speed climb (faster A/S than the Japs) to make another high energy diving attack.

In ETO the 109 and 190 had about the same altitude as the 51 but we had a
few mph on them. Again not bleeding off energy was the best combat tactic.
Some friends of mine told war stories about having a 109 on their tail and
to get away they made full throttle dives. The 109 had bigger troubles in max velocity dives so many German pilots would not follow a high speed dive.

On flaps. A small amount of flaps would reduce your turn radius and increase
your rate but the additional drag caused you to bleed off airspeed faster
than clean. With the loss of energy you could not fight the bird the best.
Also to put flaps down you had to put your head in cockpit and could lose
track of others in fur ball. Suffice to say, I never used flaps in a dog
fight."

So, here we have two guys with solid to world class credentials. Between them they have about 6,000 hours in Mustangs. Neither one has any definitive experience using flaps in combat or simulated combat. It was something they just didn't do...

I asked John if he knew of any P-51 jocks who had used flaps in combat. He will ask around, but tells me that the number of WWII Mustang pilots he knows is getting pretty small.

So, no concrete answers as of yet.... Will keep digging.

My regards,

Widewing
Title: P-51 Airfoil and Turn Performance
Post by: MiloMorai on September 05, 2007, 06:45:49 AM
Quote
Originally posted by Viking
There are such "hard evidence" for other aircraft such as the Spitfire with regard to turning circle with and without flaps. Why not for the Pony?
Did not the Spit not have 2 position flaps, 'up' and 'down', unlike the 109 and P-51 which had variable flaps?

'Down' is something like 80*, so would act like speed brakes would they not?
Title: P-51 Airfoil and Turn Performance
Post by: hitech on September 05, 2007, 10:30:31 AM
I know of 2 pilots who have done fighting in the p51, and both used 1 notch flaps when slow.

Pilots were Bob Shaw, and Me.


Dale
Title: P-51 Airfoil and Turn Performance
Post by: Tilt on September 05, 2007, 10:38:11 AM
Quote
Originally posted by Widewing

So, no concrete answers as of yet.... Will keep digging.

My regards,

Widewing


Thanks for that Widewing............ P38's and the odd Blooo bird apart it has always seemed to me that flaps were not a "tool of combat" as we use them in game.

I know of anecdotal 109 stories about flap use but these are each told as if the occurance was unusual or uncommon. It has always seems to me that the split/plain flap is primarily an aid to take off and landing (as stated in every pilots manual)........... not a combat turning aid...........and instinctively they just look like damn big air brakes to me.

but then we dont typically exercise our in game air combat as was done historically............

Maybe the drag model on all non fowler (like) flap systems in AH (except the P51) is too light.
Title: P-51 Airfoil and Turn Performance
Post by: Mike Williams on September 05, 2007, 11:40:01 AM
Use of flaps by P-51 pilots during combat?

Absolutely:

1st Lt. Louis H. Norley (http://www.wwiiaircraftperformance.org/mustang/combat-reports/4-norley-8april44.jpg)  "I dropped 20 degree flap and easily out turned him."
1st Lt. Paul S. Riley (http://www.wwiiaircraftperformance.org/mustang/combat-reports/4-riley-22april44.jpg) "Letting down 20° of flaps, I could get on the inside of the turn and pull deflection."
2nd Lt. Grover C. Siems (http://www.wwiiaircraftperformance.org/mustang/combat-reports/4-siems-12may44.jpg)  "Observing that I was overtaking too fast, I pulled up over the right e/a and dropped flaps."
2nd Lt. Frank E. Speer (http://www.wwiiaircraftperformance.org/mustang/combat-reports/4-speer-24may44.jpg)  "I had to put down 20° flaps to keep from overrunning him, indicating above 500 m.p.h."
1st Lt. Thomas D. Shank (http://www.wwiiaircraftperformance.org/mustang/combat-reports/55-shank-19sept44.jpg)  "I dropped full flaps and placed myself directly astern of the e/a on the extreme right of the formation."
1st Lt. Frank E. Oiler (http://www.wwiiaircraftperformance.org/mustang/combat-reports/78-oiler-14jan45.jpg) "I got into a Luftberry at 1100 feet with the FW 190, and with the use of flaps I got on his tail in two turns."
1st Lt. Chris J. Hanseman (http://www.wwiiaircraftperformance.org/mustang/combat-reports/339-hanseman-10june44.jpg)  "I cut my throttle and turned inside of him, dropping 20 degrees of flaps."
2nd Lt. Chris J. Hanseman  (http://www.wwiiaircraftperformance.org/mustang/combat-reports/339-hanseman-24may44.jpg) "…dropped 20 degree flaps…"
Harold W. Scruggs (http://www.wwiiaircraftperformance.org/mustang/combat-reports/339-scruggs-24may44.jpg)  "I lowered about 10 degrees flaps and made two 360 degree turns in which I gained rapidly on the E/A…"
Capt. Bradford V. Stevens (http://www.wwiiaircraftperformance.org/mustang/combat-reports/339-stevens-12sept44.jpg)  "…I was able to turn inside the Me 109 after dropping 20° flaps."
2nd Lt. Myer R. Winkelman (http://www.wwiiaircraftperformance.org/mustang/combat-reports/339-winkelman-6aug44.jpg)  "I put down 20° flaps and got on his tail."
2st Lt. S. K. Moats (http://www.wwiiaircraftperformance.org/mustang/combat-reports/352-moats-29july44.jpg)  "I dropped 20 degrees flaps and after 2 more turns I was closing on the tail of the E/A."
Lt. Glennon T. Moran (http://www.wwiiaircraftperformance.org/mustang/combat-reports/352-moran-27may44.jpg)  "We fought for about 20 minutes and it was necessary for me to put down combat flaps three times in order to turn with him."
Major George E. Preddy (http://www.wwiiaircraftperformance.org/mustang/combat-reports/352-preddy-21june44.jpg) "He turned into me and I dropped 20 degrees of flaps, out turning him."
1st Lt. Arthur C. Cundy (http://www.wwiiaircraftperformance.org/mustang/combat-reports/353-cundy-14jan45.jpg)  "With throttle pulled back and full flaps down, I overshot this 190."
1st Lt. William J. Cullerton (http://www.wwiiaircraftperformance.org/mustang/combat-reports/355-cullerton-2nov44.jpg)  "I started to overshoot so I dropped full flaps and gave him another long burst just as he was leveling off to land."
Capt. Walter V. Gresham (http://www.wwiiaircraftperformance.org/mustang/combat-reports/355-gresham-15aug44.jpg)  "I downed 40 degrees of flaps and got in another burst which hit him hard."
>Capt. Fred R. Haviland (http://www.wwiiaircraftperformance.org/mustang/combat-reports/355-haviland-21june44.jpg)  "At 1,000 feet, I dumped 20 degree flaps and made a turn inside him and started to get within firing range, when the E/A made an abrupt turn, snapped over and crashed into the ground, exploding as he hit the ground."
2nd Lt. Esward Moroney (http://www.wwiiaircraftperformance.org/mustang/combat-reports/355-moroney-2nov44.jpg) "...I put down full flaps and closed on the E/A."
1st Lt. Harold W. Spencer, (http://www.wwiiaircraftperformance.org/mustang/combat-reports/355-spencer-16aug44.jpg) "I dropped full flaps to keep from overrunning and fired from dead astern at about 100 yards and as I went over him, the Jerry popped his stick forward and crashed."
Capt. Clarence E. Anderson (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-anderson-30april44.jpg) "By using 20°  flaps and full throttle I pulled around on their tails in one turn and started firing…"
Capt. Leonard K. Carson (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-carson-2nov44.jpg)  "I chopped my throttle and dropped flaps."
1st Lt. Leonard K. Carson (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-carson-30may44.jpg) "I dropped flaps and turned back behind him."
Capt Robert W. Foy (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-foy-18nov44.jpg) "I lowered flaps and gave E/A a short burst."
Capt. Robert W. Foy (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-foy-25july44.jpg) "He suddenly pulled into a sharp right turn and I put down 20° flaps and followed giving several bursts with about two radii lead."
1st Lt. Gilbert M. O’Brien (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-obrien-27may44.jpg)  "I slid right up beside him with my flaps down.  He bailed out as I was alongside of him, at about 12,000 ft.  His chest was covered with blood and he hit the rudder."
Capt Richard A. Peterson (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-peterson-6oct44.jpg) "I realized I was over running him and lowered flaps as I pulled along side of him."
1st Lt. James R. Sloan (http://www.wwiiaircraftperformance.org/mustang/combat-reports/357-sloan-24dec44.jpg) "In the ensuing combat I was unable to turn inside the E/A until I dropped 10 degrees of flaps."
F/O Boyd N. Adkins (http://www.wwiiaircraftperformance.org/mustang/combat-reports/359-adkins-24oct44.jpg) "I dropped flaps and slid in trail with him at close range."
1st Lt. George F. Baker (http://www.wwiiaircraftperformance.org/mustang/combat-reports/359-baker-11sept44.jpg) "I dropped flaps to stay astern of E/A."
Capt. William C. Forehand (http://www.wwiiaircraftperformance.org/mustang/combat-reports/359-forehand-30may44.jpg) "I dropped twenty degrees of flaps and cut my throttle and closed in behind him firing from approximately 100 ft.”
1st Lt. Frank O. Lux (http://www.wwiiaircraftperformance.org/mustang/combat-reports/359-lux-16aug44.jpg) "I closed on him, dropped about 10 degrees of flap, and started to fire."
1st Lt. James L. McCubbin (http://www.wwiiaircraftperformance.org/mustang/combat-reports/364-mccubbin-2dec44.jpg) "The e/a then dropped his wheels and I dropped 20° flaps to stay behind."
Lt Elmer A. Taylor (http://www.wwiiaircraftperformance.org/mustang/combat-reports/364-taylor-24aug44.jpg)  "I dropped 20°  Flaps and outturned him."
Title: P-51 Airfoil and Turn Performance
Post by: Angus on September 05, 2007, 11:51:54 AM
T.E. Jonsson had to use flaps to turn inside a 190, which he promptly did, forcing the enemy pilot to bale.
He had damaged the 190 so a mechanical failiure made the 190 drop the UC on one side. The 190 took a turn into the drag and turned like the devil. So he needed one notch to turn the table.
With a 109 he said "not to worry, and you could outrun and outdive them anyway in a P51"
vs a Spitfire IX he made a grin, and said that in a knifefight the Spit was better. And a P51 could not expect to turn with it.

But these are anecdotes.......
Title: P-51 Airfoil and Turn Performance
Post by: Badboy on September 05, 2007, 03:48:39 PM
Quote
Originally posted by hitech
I know of 2 pilots who have done fighting in the p51, and both used 1 notch flaps when slow. Pilots were Bob Shaw, and Me.


Sounds like an interesting story, care to share?

Badboy
Title: P-51 Airfoil and Turn Performance
Post by: Ack-Ack on September 05, 2007, 04:57:49 PM
Quote
Originally posted by hitech
I know of 2 pilots who have done fighting in the p51, and both used 1 notch flaps when slow.

Pilots were Bob Shaw, and Me.


Dale


Who won?


ack-ack
Title: P-51 Airfoil and Turn Performance
Post by: Rebel on September 05, 2007, 05:24:06 PM
bah.  nevermind
Title: P-51 Airfoil and Turn Performance
Post by: Tilt on September 05, 2007, 05:52:53 PM
Quote
Originally posted by Mike Williams
Use of flaps by P-51 pilots during combat?

Absolutely:
 


............ seems pretty conclusive
Title: P-51 Airfoil and Turn Performance
Post by: Kweassa on September 06, 2007, 03:44:43 AM
Quote
............ seems pretty conclusive


 They're the guys that used flaps, and lived to tell about it. The really intersting thing would be what the dead people, rest their souls, have to say about it.

 I don't doubt people did use flaps for combat, and I don't doubt at some point a pilot with enough combat experience, will feel more or less confident enough to try and do something they've not done before - especially if some of their own squadron's veterans would actively teach, and advocate the use of more aggressive dog-fighting tactics, rather than just sticking to the "basics". I also don't doubt some squadrons, with some specific pilots of notable performance records, might have adopted the use of the flaps as a whole.


 ..

 What I do doubt, is how the stories of such "frequent use of flaps" fits in with the world of average pilots.

 Those sometimes with little combat experience, who stumble over their own controls inside the cockpits, and in other times would fiddle with the levers and buttons in the wrong way in midst of the confusion of combat, and would accidentally damage their own engines. Stories of very typical pilots like Lawrence Thompson, who during combat with a German Bf109G-14, engaged flaps at some point and actually forgot to retract them, thus causing a one in a million lucky stall that enabled him to escape from the 109.

 Or, the basic doctrine of keeping things as simple as possible inside the cockpit, where the more a pilot has to fiddle around, the more the danger of a misinput or a slip of concentration.


 None of the above, would fit into those pilots who can be called "skilled", of course. But then again, how many of those pilots are in a typical airforce? Those who would regularly step over the line drawn and set by the HQ, do some things that their superiors tell them not to do, and still emerge victorious, and live long and a happy life after the war?


 
 Just curious.
Title: P-51 Airfoil and Turn Performance
Post by: Charge on September 06, 2007, 07:22:38 AM
IMO the deployment of flaps and choice of dumping you E in aircombat is a rather big risk and is done in situations where you can afford to do it i.e. no other imminent threat around. I'm not sure what kind of opposition those P51s in those anecdotes were facing but the choices those pilots were making sound like bold ones. In some cases drop flaps and dump E and get one good shot in and live to tell about it...

-C+
Title: P-51 Airfoil and Turn Performance
Post by: Wmaker on September 13, 2007, 05:42:16 PM
Quote
Originally posted by Neil Stirling
109 G-2 R N.228 used in the trials was not fitted with under wing cannon.  

http://www.wwiiaircraftperformance.org/mustang/mustang-tactical.html

http://www.acompletewasteofspace.com/modules.php?name=Forums&file=viewtopic&t=10048&start=30


Sorry, missed the thread for a while...

Eric Brown describes Air Fighter Development Squadron's trials using TP814 against Spifire LF IX, Spitfire XIV and Mustang III yielding the exact results that are being talked about here. At least he makes it easy to misunderstand the identity of the G-6.

I was commenting to Widewings comment about the Mustand III. There isn't any comparisons with a Mustang III in the US testing report.

In Finnish testing with 109G-2 360 degree turn took 22 seconds with speed through the turn being 360km/h. I can't see a reason why G-6 would be significantly behind that time. I think it is very comparable with other fighter aircraft produced at the time.

EDIT/ Here is the test I was talking about:

http://www.wwiiaircraftperformance.org/me109/me109g6-tactical.html /EDIT
Title: P-51 Airfoil and Turn Performance
Post by: Knegel on September 13, 2007, 09:58:51 PM
Hi Wmaker,

d you know the condition of turn of the G2(altitude, power setting, slats in or out)?.
360km/h seems to be a rather soft sustained turn.

btw, iam somewhat suprised about the Tempest vs the G6-R6.

Greetings,

Knegel
Title: P-51 Airfoil and Turn Performance
Post by: Wmaker on September 14, 2007, 11:43:35 AM
Hi Knegel!

I understand it sounds soft because it is. :) He used constant 360km/h speed through the turn. That makes a pretty huge turning radius but because the speed is high the time is probably very similar (maybe a bit longer) compared to tightest possible turn with slats out.

So in the test:

- Slats shut
- Bank angle 70 degrees
- 1000m altitude
- 1.3 ata/ 2600rpm powersetting

Pekka Kokko states that in order to make a tighter turn you needed to throttle back below 350km/h and let the slats come out.

All my speculation, but I think here could be the problem that British test pilots ran into aswell. If they were turning with the Mustang throttle firewalled and weren't really accustomed to the heavy control forces of the 109 they were turning with a huge 350m radius. IF this was the case it could easily seem that the Mustang outturns 109G-2 easily. 109 wasn't the easiest fighter plane out there to fly to its strenghts, that's for sure.
Title: P-51 Airfoil and Turn Performance
Post by: Knegel on September 16, 2007, 12:54:52 PM
Hello again,

do you know why they did need to throttle back to turn more tight?? Shouldnt it be possible to pull the stick until the slats open, to turn with full power??
Afaik as faster a plane fly as less thrust a propeller plane have, and so i guess a full power flight with max CL(open slats) should be more tight and with a faster turn rate(with the more constant thrust of a jet engine thats different).
According to all sources i know, the elevator was absolutly not heavy at 350km/h, at 350mph it did start to stiff up.
The 109E4 did turn with just above 200km/h and i once did guess the G2 would do the job with around 260km/k, just like in AH. 100km/h more would add a huge amount of drag, reduce the efffective thrust much and the low AoA would increase the radius much.

Is it possible that the document include a mistake and it should be 260km/h?? Otherwise the best turn rate must be better.

btw. In EAW the 109G2 need almost exact 22sec for 360°, with 360km/h at 1000m, the min turnspeed in this hight, with max power, is 255km/h, the resulting time is 18sec.
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on September 29, 2014, 01:07:10 PM
BTW what was the effect of the forward joint extension in D model? IIRC it was deleted in later models.

"The F4U wing leaks air from underside to top side."

The effect of that is also measured in the same document and the effect seems to be quite minimal according to figure on page 610. The low Cl is puzzling. On page 606 the Cl figure is again different.

The left wing was modified with a wing fence to mitigate the early stall of the left wing at landing speeds

It must be noted though that the speeds where measurements were done were quite small as they were below 100mph (60mph). Their loaded performance in higher speed is probably somewhat different.

What ever the profile performance is that is only one variable in the equation although a significant one when trying to figure the performance at the edge of the flight envelope. It seems that although both P51 and FW190 had a twist i.e. washout in wing they both suffer from somewhat sudden loss of control and the twist does not seem to do what it is supposed to which is to provide delay and warn of stall -or maybe the stall actually is less abrupt than it would be without the twist. What 190 wing behaves like that is a mystery to me since it uses a more conventional airfoil.

The FW 190 had zero twist on the outboard 20% of the wing. IMO that contributed to the vicious high speed stall in high G turns. I have heard without proof so far that the wing was less stiff torsionally than say a 51

I think this table gives some idea of the relative behavior of wing sections.
(http://www.lv36.org\kuvat\AD_pg106.jpg)

Source: Abbott&Doenhoff 1949 "Theory of Wing Sections"

-C+

PS. Bah, it doesn't show....
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on September 29, 2014, 01:35:17 PM
i aint no good with numbers or figures like you guys and reading some of these well done graphs etc is great but.....

maybe the P51 of old was wrong and the current one is right?



the P51 wasnt the greatest low-med alt dogfighter, it was a high alt escort plane, it was designed for long runs to berlin and back, nothing more really.According to Rall it was the best of the Allied fighters based on his experience at Rechlin following his wound on May 12, 1944.  That impression was based on the combined maneuverability and range. He didn't state that it was as maneuverable as the Spitfire or better than the 109.

Additionally, it was designed as 'a better fighter than the P-40. It was the Brits, however that instantly realized that it was not only a delight to fly but its performance potential was potentially superb with the Merlin 60 series engine. While the Spit could out climb a turn the Mustang I, the Mustang was 30 mph faster at same power settings up until FTH of the Allison.


P51's only really won dogfights because there was so many of em, plus better training on fighting tactics, something that was starting to lack in German pilots by the end.

P-51s did Not outnumber the LW attacking forces until near the end of the war simply because the LW knew where they would attack and from zero to perhaps two Fighter groups covering say six bomb groups out of 35 and a 70 mile stretch would be available to engage 50 to 250 German day fighters into that small volume.  Read the history of the 8th FC on deep escorts from December 1943 through May, 1944 when the total long range escort force was one to eight Fighter Groups (including P-38s) taking 1000 to 1500 bombers in three BD to three to six separate targets scattered from Berlin to Posnan to Munich.

In other words the LW died because in many cases they didn't have the speed to disengage, and only marginal maneuverability advantage when flown by equal pliots.   If say a 190G6 A/S could outclimb a 51 by 500fpm that is moving away at 6mph/8.8 fps - that doesn't out run a 50 cal starting at 2800 fps.


but in game, everyone (err mostly) knows there planes inside out, so its good pilots getting the most out of there planes, hence the P51 in a 1on1 will not be that great. if it was a 3to5 on 1  (p51 vs 109) then the results would match real life?



i know this a rubbish point to put forward without figures etc but its just the way i see it.

Go find whatever figures make sense to you but consider this set.

During Big Week Feb 20-25 there were Nine P-47D (4, 56, 78, 353, 355, 356, 358, 359, 361) fighter groups, two P-38 (20, 55), and two P-51 (354 and 357).All flying escort, and all the targets were deep, out of range in general from the P-47s. Both 8th and all 9th AF fighter groups flew long range escort until the end of May which is why the effective operational numbers increased for the P-47 data below

Credits for e/a Destroyed 2/20 - 2/25
P-38  10
P-47  78
P-51  64

For 2/20-3/31
P-38 35   (3 P-38 FG's)
P-47 316 (11 P-47 FG's)
P-51 318 (4 P-51FG's)

Source USAF 85 Air Victory Credits WWII
Title: Re: P-51 Airfoil and Turn Performance
Post by: The Fugitive on September 29, 2014, 01:40:12 PM
I don't think anyone was waiting around for 7 years for those answers, but thanks.
Title: Re: P-51 Airfoil and Turn Performance
Post by: BnZs on September 29, 2014, 02:53:53 PM
A Pony that turned much better would be a liability to Aces High. Its popularity already almost demands perking, yet perking the ONE plane the average new subscribers is most likely to want to get in immediately would be deleterious to retaining new subscribers. Thus the turn performance of the Pony we currently have is what we will continue to have, out of what could reasonably be called necessity.
Title: Re: P-51 Airfoil and Turn Performance
Post by: Stoney74 on October 09, 2014, 11:14:08 PM
So, after a 5 year absence, imagine my surprise when I stumbled in here tonight to find this still on the 2nd page of the Aircraft and Vehicles forum...  Holy necro!
Title: Re: P-51 Airfoil and Turn Performance
Post by: Gaston on October 11, 2014, 01:27:42 AM
  
  Are you really sure want to know how the P-47D and the Merlin P-51 compared in real life?


  Quote, KG 200: (early captured Razorback without full power available, and with needle tip prop) "The P-47D out-turns our Bf-109G"

    Bf-109G vs P-51B: "The P-51 has a dangerous stall which killed two of our pilots"

  Source: On Special Missions: The Luftwaffe's Research and Experimental Squadrons 1923 - 1945 (Air War Classics)

  Sounds like they are not saying the Merlin P-51 out-turned the Me-109G... (Maybe that's why I heard of two 15 minutes continuous turning fights, all to one side without any gain (45 X 360° turns), and even of one that went on for half an hour! (90 X 360° turns)...

  P-47D vs the Me-109G is more like 3X 360° turns and bye bye Gustav, or rather, to mention one memorable Lufbery quote (at 20 000 ft): "They went around with us in a Lufbery for two turns, and then they quicky lost interest and rolled out"

  They lost interest you know...

  

  Let me opine here for a sec: Hanging on to 1940's test flights, a time when the in-flight procedures were not scrutinized correctly, will usually only produce what that particular vintage test was expected to produce...

   What do you know, the 1989 SETP test flight using modern test flights method produced results largely in agreement with the combat record:

======================================

  Quote, 1989 SETP test: "Heading Change Time (180 deg at METO, 220 KIAS at 10,000 ft.)
FG-1--8.5 sec P-47--9.7 sec F6F--9.9 sec P-51--10.0 sec"

====================================================

  So for the P-47D 9.7 sec for a 180° at moderate speed vs 10 seconds P-51D, no matter what the wingloading says...

  The P-47D's superiority would have probably been more evident at a lower speed (unless maybe the P-51 seriously downthrottled, coarsened the prop pitch, and dropped 20° of flaps at around 180 MPH IAS, but that's a whole other thread).


=======================================

  Quote 1989 SETP test: "AIR-TO-AIR TRACKING 210 KIAS at 10,000 ft. (straight & level into a 3g
turn to the left building to 4g followed by a hard reversal into a 4g
right turn.)
FG-1 best, followed by P-47, F6F and, trailing badly, the P-51."

==========================================

  I don't know what more needs to be said when you read a few combat reports, and you see most of what they did in the P-47D was turn, all the way down to the deck at 140 mph...

  One of the few Western European fighters that could more than hold its own in low speed sustained horizontal turns with the the P-47D was of course, you guessed it, the FW-190A! But rather than list all the instances of Spitfires getting out-turned by it at low speed (longuish), how about focussing on the ONE thing the FW-190A Absolutely HATED?

  
======================================

 A translated Russian article from "Red Fleet" describing Russian aerial tactics against the German FW-190, from Tactical and Technical Trends, No. 37, November 4, 1943.

  Quote:

  -Since the FW-190 is so heavy and does not have a high-altitude engine, pilots do not like to fight in vertical maneuvers.

  -Being very stable and having a large range of speeds, the FW-190 will inevitably offer turning battle at a minimum speed.

  -In fighting the FW-190 our La-5 should force the Germans to fight by using the vertical maneuver.

  -Throughout the whole engagement with a FW-190, it is necessary to maintain the highest speed possible. The Lavochkin-5 will then have, when necessary, a good vertical maneuver, and consequently, the possibility of getting away from an enemy attack or on the contrary, of attacking.

==============================================

  Man, I think the Fw-190 doesn't like vertical maneuver, y'know... But it's not done saying it...:

==============================================

   Osprey "Duel" #39 "La-5/7 vs FW-190", Eastern Front 1942-45:

P.69 "Enemy FW-190A pilots never fight on the vertical plane.---The Messerschmitt posessed a greater speed and better maneuverability in a vertical fight"

P.65 Vladimir Orekov: "An experienced Fw-190A pilot practically never fights in the vertical plane"

==========================================================

  Man! I think it is possible the Fw-190A doesn't like the vertical plane...

  But what the heck DOES it like?:

  ================================

  Red Fleet, No. 37, November 4, 1943.:

  -The speed of the FW-190 is slightly higher than that of the Messerschmitt; it also has more powerful armament and is more maneuverable in horizontal flight.

  -A fairly good horizontal maneuver permits the FW-190 to turn at low speed without falling into a tail spin.

 -Being very stable and having a large range of speeds, the FW-190 will inevitably offer turning battle at a minimum speed.

============================================================

  Weirner Steiz: "The 190 was a much better aircraft than the 109: You could curve it"

==============================================================

I could go on, but you know...


  And just in case you really wanted to know how the P-47D and the P-51 actually compared in turning ability (and I mean really!), read this, but just before, allow me a disclaimer: [warning, not for the faint of heart]


========================================

  Osprey, P-47 Thunderbolt units of the 12th Air Force.
 
  P.32: 15th May 1944, 87th Fighter squadron operational report (Paddle-blade propellers only started to be delivered to the group in late May 44, and only with new aircrafts, so all these are needle-tip props, which does explain in part their turning performance).
 
  That afternoon, the 87th FS took off (16 aircrafts) with 32 X 1000 lbs bombs underwing to add to the destruction in Acquapedente. Target Acquapedente bridges.
 
  "A flight of 15 Me-109s and 5 FW-190s was encountered. One section kept the fighters occupied while the remainder attacked the bridges. Three enemy fighters were destroyed for one of ours damaged.
 
  A gratifying result of this engagement was that a P-47, not considered a low-altitude aircraft, can maneuver advantageously with Me-109s almost on the deck, even though under the handicap of being on a bomb run." (2 X 1000 lbs of bombs underwing)

  =====================================================================

  Yes guys, he does mean the P-47D out-dogfighted the Me-109Gs on the deck with 2X 1000 lbs bombs underwing, because otherwise they would not be handicapped and on a bomb run, and dropping the bombs would mean the mission for all these bomb-dropping aircrafts would be a failure, and that's a success for the enemy and thus not gratifying...

  Feel free to hate my totally unreasonable interpretation, you know you want to...

  
 
   So how does the P-51 do against Me-109Gs (but without 2000 lbs of bombs hanging from it?, Chhh!):

======================================================================

   "The P-51 Mustangs of Major George Preddy" EC # 100, Eagles Editions limited.

   P.20: "Preddy spotted two 109s and got into a Lufbery with the first one. Neither was gaining much advantage when all of a sudden another 109 cut in front of him."

===================================================
 
     Osprey, RAF Mustang and Thunderbolt Aces, P.42:
 
   Sq. Lt. Hearner (No 19 Sq) commenting 11 April 1945 battle over Lister airfield (P-51 Mk IV vs late Me-109Gs or Ks):
 
  "The 109s we encountered were obviously an experienced bunch of boys. Their turning circle is decidedly better than ours at low speed. The lowering of 20 degrees of flaps may just enable us to hold them in the turn, although I feel they could outclimb us." (Note: RAF P-51s of this period typically used 80 inches of manifold pressure boost with 150 octane fuel, higher than the 72 inches US Mustangs used in Europe. Similar boost to RAF 80" boost was only used in Iwo Jima by the USAAF.)

=================================================

  

  And how about the Spitfire while we are at it?:

  In "Le Fana de l'Aviation" #496 p. 40: " Les premiers jours furent marqués par des échecs dus à une tactique de combat périmée dans le plan horizontal, alors que le Spitfire était particulièrement adapté au combat dans le plan vertical."

Translation: "The Spitfire failed in horizontal fighting, but was particularly adapted to vertical fighting"

  And of course Johnny Johnson's dogfight with a FW-190A: Quote: "Opposite sides of an ever diminishing circle... I asked the Spitfire for all she had... It was just a matter of time and he would have me in his sights..."

  But you don't think you were getting away from reviving this thread without my pal John Weir did you? :

  ""A Hurricane was built like a truck, it took a hell of a lot to knock it down. It was very manoeuvrable, much more manoeuvrable than a Spit, so you could, we could usually outturn a Messerschmitt. They'd, if they tried to turn with us they'd usually flip, go in, at least dive and they couldn't. A Spit was a higher wing loading..."
"The Hurricane was more manoeuvrable than the Spit and, and the Spit was probably, we (Hurricane pilots) could turn one way tighter than the Germans could on a, on a, on a Messerschmitt, but the Focke Wulf could turn the same as we could and, they kept on catching up, you know."

  Yeah, Y'know...

  Gaston

  

  

  
Title: Re: P-51 Airfoil and Turn Performance
Post by: Scherf on October 11, 2014, 04:54:42 AM
God, not Gaston again.

Fargin necro.
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on October 11, 2014, 01:03:05 PM
The use of flaps to improve turn performance was useful only briefly in order to gain a short lived tighter turn in order to get a better deflection shot.  The 51 Flap was a big beast compared to the maneuvering flap on say a 109 or even a P-38.

There are many 8th AF encounter reports of good pilots chasing 109s that deployed flaps for small temporary improvement accompanied with a decided loss of speed.  John C. Meyer had just such an encounter on May 12 in which the 352nd FG attacked a German force north of Frankfurt.  The encounter report is on Spitfireperformance.com website within the P-51 Merlin tab. scroll to the bottom for Encounter Reports and go to 352nd FG

http://www.spitfireperformance.com/mustang/combat-reports/352-meyer-12may44.jpg
Title: Re: P-51 Airfoil and Turn Performance
Post by: Gard06 on October 14, 2014, 01:20:35 PM
What we should be asking, "Why is the p51D under modeled in this game". 
Here are the true numbers for the pony....  HTC is way off and below these.

Flight Test Engineering Branch
Wright Field, Dayton, Ohio
15 June 1945

Flight Tests on the North American
P-51D Airplane, AAF No. 44-15342

Summary

       Fuel consumption and speed data listed in the flight operation instruction chart have been spot checked by duplicating in the test program some of the power settings shown in the T. O. By comparing the results obtained with the T. O. figures, a quick estimate of the validity of the T. O. may be made.

       High speed and climb performance have been obtained on this airplane at a take-off gross weight of 9760 pounds. Performance was obtained up to an altitude of 35,000 feet in increments of 5000 feet in a clean configuration. The clean configuration included one external bomb rack on each wing. Additional configurations were flown at 5000 and 15,000 feet including two 110 gallon tanks, two 500 pound bombs, and two 250 pound bombs. The principal results are as follows:

       A.  Clean Configuration (with bomb racks).

   1.   Maximum speed at critical altitudes   
       
      High Blower   
   
      War Emergency power (3000 RPM and 67") 26000'   442 MPH
      Military power (3000 RPM and 61") 28000'   439 MPH
      Normal Rated power (2700 RPM and 46") 29400'   420 MPH
   
      Low Blower   
   
      War Emergency power (3000 RPM and 67") 10000'   417 MPH
      Military power (3000 RPM and 61") 13200'   413 MPH
      Normal Rated power (2700 RPM and 46") 16200'   387 MPH
   
   2.   Maximum speed at sea level   
       
      War Emergency power (3000 RPM and 67")   375 MPH
      Military power (3000 RPM and 61")    364 MPH
      Normal Rated power (2700 RPM and 46")    323 MPH
       
   3.   Rate of climb at critical altitude.
       
      War Emergency power (3000 RPM and 67") high blower (19,000')   3200 ft/min.
      War Emergency power (3000 RPM and 67") low blower (4,800')   3600 ft/min.
       
   4.   Time to climb to service ceiling, war emergency power
3000 RPM and 67") (41600')   28 minutes.

       B.  True speed loss, MPH from clean configuration due to external load items (2700 RPM and 46").

2-110 Gal. Tanks   2-500 Lb. Bombs   2-250 Lb. Bombs
5000 ft. 45   36   25
25000 ft. 47   33   2



Notice in Aces High the spec's on the p-52d at sea level doesn't even go over 360mph....   Why is that HTC?   
Title: Re: P-51 Airfoil and Turn Performance
Post by: Widewing on October 21, 2014, 05:40:19 PM
In game, the P-51D can reach 367 mph at 50 ft ASL with 25% fuel.

Less than 375 mph, but speeds varied with the aircraft as not all aircraft are maintained the same. There was and always would be some normal variation from plane to plane....
Title: Re: P-51 Airfoil and Turn Performance
Post by: Skull-1 on October 25, 2014, 11:45:58 AM
The Mustang is undermodeled because if it weren't.....everyone would fly it.

It is a legendary and iconic airplane.  That's one of the main reasons people fly it.  Visibility is a factor.  The ability to disengage as well.

Still, as porked as it is, the real deal is overrated.   Pony pilots say they could turn with the Germans all day long.  German pilots say the opposite.

At the end of the day, my friend Chris Avery (CAF Hawg pilot) says the F4U can beat anything with the Sea Fury being the toughest opponent.   That's his opinion as I recall it.  I could be wrong.
Title: Re: P-51 Airfoil and Turn Performance
Post by: DaveBB on October 25, 2014, 03:48:52 PM
Pilot skill is such a huge variable, that the only way to compare two aircraft is to compare the test data.  Chuck Yeager flew against some USAF Colonel in mock dogfights when they captured a Mig-15.  Chuck beat him both in the Mig-15, and when they switched, he beat him again in the F-86.
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on October 28, 2014, 01:46:28 PM
The Mustang is undermodeled because if it weren't.....everyone would fly it.

It is a legendary and iconic airplane.  That's one of the main reasons people fly it.  Visibility is a factor.  The ability to disengage as well.

Still, as porked as it is, the real deal is overrated.   Pony pilots say they could turn with the Germans all day long.  German pilots say the opposite.

Turning with another fighter in a sky full of predators is over rated, but I have listened to two sides of a conversation between my father, Henry Brown (Who out turned five 109s in a Lufberry with no ammo to distract them from two of his 354FS buddies, forcing each one to bail as he closed on the next one) Gunther Rall and Steinhoff while 109 vs 51 attributes were discussed.  As you might expect, highly respectful and detailed shared experiences. To my knowledge Rall engaged with but never filed a claim for a 51.  The outcome of the discussion is that at low to medium speeds the 109 had an advantage in acceleration (slight and hard to measure), turn and climb (also hard to measure- but Marshall and Brown both agreed that if a good pilot was in the 109 he could make a steep rh climbing turn that the 51 couldn't match. The 51 was faster to much faster until the 109K, could roll and turn better at high speed/high G and outdive (slightly) the 109. 

Conclusion - best pilot with equal or better tactical position has advantage with agreement that the 51 could 'do it' everywhere in Europe from England and Italy while the 109 has to seriously disengage if possible after 90 minutes.


At the end of the day, my friend Chris Avery (CAF Hawg pilot) says the F4U can beat anything with the Sea Fury being the toughest opponent.   That's his opinion as I recall it.  I could be wrong.

At the Joint Fighter Conference - Oct 1944 at Patuxent, MD over 200 reps from AAF, USN, USMC, RAF and test pilots from all the manufacturers flew YP-59, P-51D, P-63, F4U-1, F4U-4, P-47D-30, F4F, F6F, P-40N, P-39Q, P-38L, Vampire, Mosquito, P-61, F7F, Spit XIV, A6M, XF8-F and included such folks as Lindbergh, Tom Lanphier, Boone Guyton.

The rankings for Best All Around Fighter above 25,000 feet were P-47D (45%), P-51D (39%), F4U-1 (7%), F6F and F4U-4 (3% each), Seafire (2%) and P-38 (1%) in that order.

The rankings for Best All Around Fighter below 25,000 feet were F8F (30%), P-51D (29%), F4U-1 (27%), F7F (7%), F6F (2%), F4U-4 and F2G (2% each).

Best Fighter Bomber
F4U-1 (32%), P-47D (19%), Mosquito (14%), F6F (12%), F7F (11%), P-51D (7%), P-38 (5%)

Having voted and tallied opinions from so many reps of both the contractors and different Services might not be perfect - but far better than one person's opinion.
Title: Re: P-51 Airfoil and Turn Performance
Post by: Gaston on November 11, 2014, 03:01:50 PM
The use of flaps to improve turn performance was useful only briefly in order to gain a short lived tighter turn in order to get a better deflection shot.  


  Not quite. This short-lived turn superiority was true for the P-51 aircraft as a whole (it resembled the Spitfire in that respect): It could gain lead on a Me-109G, but then shuddered and stalled if the flaps were up, this happening repeatedly over a single 360 (a condition which the Spitfire could tolerate better, since it was in a very stable speed-decaying "rumble", during which it could fire accurately "accross the circle", probably the only way the Spitfire could "out-turn" anything at all...)... For the P-51 this difficulty in gaining was likely because the turn rate was similar, but over a larger diameter at a slightly higher speed, which made leading difficult.

  To exploit the flaps, they had to stay down:

   Sq. Lt. Hearner (No 19 Sq) commenting 11 April 1945 battle over Lister airfield (P-51 Mk IV vs late Me-109Gs or Ks):
 
  "The 109s we encountered were obviously an experienced bunch of boys. Their turning circle is decidedly better than ours at low speed. The lowering of 20 degrees of flaps may just enable us to hold them in the turn, although I feel they could outclimb us."

  G.
Title: Re: P-51 Airfoil and Turn Performance
Post by: FLS on November 11, 2014, 03:58:36 PM
  Not quite. This short-lived turn superiority was true for the P-51 aircraft as a whole (it resembled the Spitfire in that respect): It could gain lead on a Me-109G, but then shuddered and stalled if the flaps were up, this happening repeatedly over a single 360 (a condition which the Spitfire could tolerate better, since it was in a very stable speed-decaying "rumble", during which it could fire accurately "accross the circle", probably the only way the Spitfire could "out-turn" anything at all...)... For the P-51 this difficulty in gaining was likely because the turn rate was similar, but over a larger diameter at a slightly higher speed, which made leading difficult.

  To exploit the flaps, they had to stay down:

   Sq. Lt. Hearner (No 19 Sq) commenting 11 April 1945 battle over Lister airfield (P-51 Mk IV vs late Me-109Gs or Ks):
 
  "The 109s we encountered were obviously an experienced bunch of boys. Their turning circle is decidedly better than ours at low speed. The lowering of 20 degrees of flaps may just enable us to hold them in the turn, although I feel they could outclimb us."

  G.

In other words, the 109 and Spitfire had a lower stall speed than the P-51, and flaps lower your stall speed.
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on December 02, 2014, 11:16:43 AM
As I re-read this thread I noticed several incorrect assumptions:
First the NACA/NAA 45-100 airfoil remained throughout the XP-51, 51A/B/C/D/K and A-36.
The Wing dropped about 3" from the A to the B/C/D/K but the leading edge plan view from ~WS 61 to Root Chord steepened with the D/K wing and also changed LE incidence in that region.  The outboard twist remained the same all the way to the tip chord. For the B the washout was -0.5degree at root, 0.75 at ~ WS 50, thence to -0.85 degree at tip. For the D the washout was +0.25 degree at Root, 0.6 degree at ~ WS 61, thence constant to -0.85 degree at tip.

The two D CLmax for the NACA/NAA 45-100 was about 1.6 but of course reduced as function of Aspect Ratio. The wind tunnel and flight tests demonstrated a CLmax at approximately 1.4+ for high Reynolds no and about 1.5 for wheels up level flight Stall (Clean - no flaps) While the CLmax with Flaps was close to 1.7 (2-D), the CD of NACA/NAA 45-100 was significantly higher at CLmax. (I don't have my notes in front).

I have not seen any publication of any test that suggest a change in Oswald efficiency for any of the P-51 series including the XP-51F/G/J and P-51H with straight leading edge NACA 66-(1.8) 15.5 (at root chord) and 12% at tip.

I've read all the informed opinions and have a few thoughts based on research, knowledge of Flight Dynamics factors related to conventional aircraft, and opinions based on the above.  First - I have no idea regarding the modeling but I agree just about everything I have read by Dtango and Widewing.

The primary distinctive unknown factor between the B and D is how does the difference in Inboard wing incidence as a result of the Leading edge difference in Incidence between the Root and the intersection with the common wing around WS 61?  The second question in my mind is what the difference in yaw behavior at low to medium speeds might be between turtledeck B and teardrop canopy D versions?

In real life high G turns at corner speeds the application of yaw correction, finite and undefinable, should result in delta trim drag (Ditto and even moreso for a 109 with slats deployed - the local wingtip CL for the high wing is greater than lower wing in greater proportion I would think than for a P-51 which in turn requires slightly more rudder input (and drag) to carve the turn)?

After those considerations, the model (IMO) requires derivation with respect to time the following:
Change of drag (dominated by pressure drag as function of lift/AoA) as function of CL as change to velocity and angle of attack occurs from the velocity entering the turn to steady state sustainable velocity in a constant altitude, constant speed turn.
Change to propeller efficiency as the aircraft reduces speed. Shouldn't be much but worth exploring along with trim drag contributions to the T=D equations.

As to some of the other stuff commented on here.  A Bf 109 (and FW 190) terminal dive speed was less than that of a 51 and a 47. Having said that, with a head start it might get away but the test docs state that 475mph at ~ .72M for 1G dive limit was about all the average 109 should attempt. In addition, the 51 did not suffer the lower speed (than .65 to .72M) compressibility issues that all conventional NACA 23xxx in same 12 to 15% T/C conventional airfoils suffered.  The laminar flow wing with T/C at ~ 39% made a huge difference in the drag rise regime.

The other complications when modeling dissimilar engines is the plug of HP as a function of altitude and gear stages when comparing say a P-51 and a Bf 109 or FW 190.. as well as stick forces for both roll and high G/high speed turns...It seems the gamers need to input a reasonable (and constant) stick force table for each separate combatant.
 
 
Title: Re: P-51 Airfoil and Turn Performance
Post by: save on December 05, 2014, 05:58:20 AM



As to some of the other stuff commented on here.  A Bf 109 (and FW 190) terminal dive speed was less than that of a 51 and a 47. Having said that, with a head start it might get away but the test docs state that 475mph at ~ .72M for 1G dive limit was about all the average 109 should attempt. In addition, the 51 did not suffer the lower speed (than .65 to .72M) compressibility issues that all conventional NACA 23xxx in same 12 to 15% T/C conventional airfoils suffered.  The laminar flow wing with T/C at ~ 39% made a huge difference in the drag rise regime.

The other complications when modeling dissimilar engines is the plug of HP as a function of altitude and gear stages when comparing say a P-51 and a Bf 109 or FW 190.. as well as stick forces for both roll and high G/high speed turns...It seems the gamers need to input a reasonable (and constant) stick force table for each separate combatant.
 
 

From P51 pilots accounts that  flew both the B and D model where in consensus that the D model had to break off when the B model P51 did not, catching 109G's in a high speed dive, due to instability.
If the 109g did not have a head start, they would die trying to dive into clouds below, experienced 109 pilots did not dive away knowing they would be easy meat.

Do you have any opinion of these accounts, Drgondog ?

 
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on December 06, 2014, 05:08:16 PM

From P51 pilots accounts that  flew both the B and D model where in consensus that the D model had to break off when the B model P51 did not, catching 109G's in a high speed dive, due to instability.
If the 109g did not have a head start, they would die trying to dive into clouds below, experienced 109 pilots did not dive away knowing they would be easy meat.

Do you have any opinion of these accounts, Drgondog ?

Yes - one anecdotal and one flight test observations.

The Mustang laminar flow wing with max T/C at ~39% had the most benign drag rise characteristics of any fighter I am aware of save the Spitfire with the thinner wing... it did Not have a pitching moment tuck similar to the 109/190/P-38 and even the P-47 with classic airfoils with max T/C at ~25%. The late model P-47D (-30?) installed a similar dive flap at about 30% C to the P-38 to lessen the impact of the forward pitching moment at Mcr. It was tested on the P-51B, found to be slightly beneficial but not enough at the 505mph TAS Vne to warrant production introduction.

The undesirable dive characteristics of the P-51B (and D) were related to Yaw and an element of porpoising near Vne. The porpoising was directly related to the fabric elevators on BOTH the P-51B and D, which was fixed when the P-51D-15 was produced and metal elevators were retrofitted (as well as dorsal fins for the P-51D-5 and all P-51B/C to improve yaw - somewhat).

There are too many combat Encounter reports in which the 'winner' (the Mustang since that pilot survived the Encounter) dove after a 109 or 190 and destroyed it in a dive.  If a Mustang broke up in a dive (somewhat rare) then there was no Encounter Report to cede the advantage to the Bf 109. The Test reports I have seen for the Bf 109 indicate Vne= 475mph, about the same as the F4U but greater than the P-38.

My father destroyed six Bf 109s plus a Ju 87 and the victory credits were (2) in a Lufberry on June 20, 1944 over Rugen Island with one each Bf 109s in turning combat - both blown up, (1) in a terminal dive chasing a Bf 109 on July 28 near Mulhausen in which the fleeing 109 was observed out of control and dove into the ground, (1) September 11 near Giessen in which he pursued and caught a  109 in a dive and blew it up, (1) September 11 in which he chased and caught a 109 on the deck and shot it down, one on August 6 Sw Hamburg in a maneuvering fight from altitude in which he caught a diving 109 then engaged in a maneuvering fight on the deck. The outcome was decided when the 109 pilot attempted a split S from 2000 feet, my father dropped partial flaps - followed itinto the Split Ess but the 109 crashed as he brought his guns to bear.

The June 6, June 20 combats were P-51C-10NT, the July 28/Aug 6/Sept 11 were P-51D-5NA.

Anecdotal combats documented and affirmed by wingman, involving turning, diving, random maneuvering and split Ess from common low altitude.

Title: Re: P-51 Airfoil and Turn Performance
Post by: Mike Williams on December 07, 2014, 07:07:53 AM
Good post Bill.
Title: Re: P-51 Airfoil and Turn Performance
Post by: save on December 07, 2014, 09:24:51 AM
Nice post, thanks
Title: Re: P-51 Airfoil and Turn Performance
Post by: Charge on December 07, 2014, 12:04:39 PM
Bf109 dive tests 1943:

max. Mach 0,805@7.0km
max. TAS 906km/h@5.8km
max. IAS 737km/h@4.5km

http://109lair.hobbyvista.com/techref/structures/tails/109.05e43_report/05e43-p2.htm

I cannot understand how yaw porpoising would be affected by fabric of metal elevators. AFAIK the porpoising of D was due to bubble canopy disturbing the flow around rudder assembly. The fillet cured the problem in level flight but not in dive.

-C+


Title: Re: P-51 Airfoil and Turn Performance
Post by: FLS on December 07, 2014, 12:21:10 PM

I cannot understand how yaw porpoising would be affected by fabric of metal elevators. -C+


Yaw and porpoising are different axis. Porpoising is pitch.
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on December 07, 2014, 03:21:12 PM
Bf109 dive tests 1943:

max. Mach 0,805@7.0km
max. TAS 906km/h@5.8km
max. IAS 737km/h@4.5km

http://109lair.hobbyvista.com/techref/structures/tails/109.05e43_report/05e43-p2.htm

I cannot understand how yaw porpoising would be affected by fabric of metal elevators. AFAIK the porpoising of D was due to bubble canopy disturbing the flow around rudder assembly. The fillet cured the problem in level flight but not in dive.

As noted by FLS 'porpoising' is an oscillation in pitch (visualize Dolphin/Porpoise). It was believed that the fabric airfoil surface 'ballooned' in high speed - in any case the metal elevators solved the problem.

The airflow as modeled by Lednicer demonstrated that the pressure distribution was better in the D than the B (or the Spitfire 9 or the Dora) - I posted it as #10 post on this thread http://www.ww2aircraft.net/forum/flight-test-data/51-performance-thread-12670.html

one of the reasons is that the slope of the windscreen is ~6 degrees more (closer to parallel with freestream velocity over the cowling) than either the P-51B and Spit IX. If you look at the modeled pressure distribution using the VSAERO CFD plus a sophisticated Navier Stokes variable mesh to look at pressure gradients in the boundary layer, you will note the differences graphically.

-C+



Title: Re: P-51 Airfoil and Turn Performance
Post by: Charge on December 08, 2014, 06:03:09 AM
According to this document the porpoising with fabrics could be encountered also at lower speeds at low altitude and the problem was remedied by metal covering up to 0.8 M. After that the plane still "wallows" in dive. There is no mention whether or not the porpoising phenomenon existed above 0.8M.

http://www.wwiiaircraftperformance.org/mustang/mustangIV-divetest.html

What I found out from P-51 D/K pilot manual that once you enter the compressibility there is not much you can do in a P-51 but to wait for the control to come back while you will lose at least 8000 feet of altitude before you have decelerated enough to begin to come out of compressibility. Mind you that P-51 does not have a flying tail where as 109 does, so it's pilot can control when he want's to come out of dive. It was quite common that these situations came as a surprise to 109 pilots and they did not always realize that all that was needed to come out of dive was a few rotations of elevator trim but rather tried to pull the stick with both hands. On one instance the indicated airspeed of a diving 109 was 850 kph so the absolute maximum dive speed was well exceeded. It was essential in the 109 that the trim was not used too much as the aircraft would tighten the pull out by itself when it decelerated, effectively ripping the elevators off the plane. I recall that at least one such incident is known.

Also from different data these aircraft seemed to share the tendency for the trim changes in different phases of the dive even if the wing profiles would suggest otherwise. It seems that the configuration of control surfaces affected this at least in P-51 which needed down trim in high speed due to fixed angle of its elevator plane (the effects of which were evident in the case of Galloping Ghost).

It actually seems that it was safer to dive faster than 0.8M in a P-51 than in a Bf109 but the problem was that in a P-51 you were a passenger during the deceleration phase where as in a 109 the aircraft could safely exceed the safety margins and you could control your exit from the dive better.

Anecdotal evidence is OK in many cases but it has to be kept in mind that in the heat of the battle the initial conditions are not known. So it somebody says that flying the X he caught the Y easily in a dive you have no way of knowing what was the initial speed of the Y to begin with. Anecdotes may give an idea of relative performance if there is no usable test data at hand.

-C+
Title: Re: P-51 Airfoil and Turn Performance
Post by: drgondog on December 08, 2014, 09:58:56 AM
The one comment - The Merlin Mustang was deemed 'controllable' at .83M (605mph TAS), while suffering structural damage. It was during the dive tests that the Vne was established at 505 mph. The tendency was for the P-51B/D to become increasingly nose heavy as the placard speed was reached - BUT it never had the change of CMac that both the P-38 and P-47 experienced - due to the laminar flow wing and the delayed onset of the compressibility shock wave.

The change of Tail plane incidence from 1 1/2 degree positive to 1/2 degree positive and replacing fabric with the metal elevator eliminated the problems  - but forced the pilot to apply more nose heavy trim prior to entering a dive.

Having said this, the 51 was controllable throughout the dive
Title: Re: P-51 Airfoil and Turn Performance
Post by: MiloMorai on December 08, 2014, 11:59:44 AM
According to my P-51D Handbook limiting max speeds:

All speeds are IAS.

40,000 ft. = 260 mph (418kph)
30,000 ft. = 300 mph (482kph)
20,000 ft. = 400 mph (643kph)
10,000 ft. = 480 mph (772kph)
5,000 ft. = 505 mph (812kph)
Title: Re: P-51 Airfoil and Turn Performance
Post by: save on December 08, 2014, 12:21:44 PM
Anyone have 190a/d series dive performance to compare with 109s and p51b/d ?
Title: Re: P-51 Airfoil and Turn Performance
Post by: Mike Williams on December 09, 2014, 10:43:09 AM
Anyone have 190a/d series dive performance to compare with 109s and p51b/d ?

Einfluss hoher Mach' Zahl auf Fw 190. (http://www.wwiiaircraftperformance.org/fw190/Fw_190_Dive.pdf)  Translation: Influence of high Mach number on Fw 190 (http://www.wwiiaircraftperformance.org/fw190/fw190-0022-dive.html)

Hochgeschwindigkeitsversuche mit Me 109 (Dive Test) (http://www.wwiiaircraftperformance.org/me109/Me_109_Dive_Test.pdf)

Compressibility Dive Tests Part I on North American P-51D Airplane (Mustang IV), AAF No. 44-14134 (http://www.wwiiaircraftperformance.org/mustang/p-51d-dive-27-feb-45.pdf)    P-51D Dive - Mach .85 (http://www.wwiiaircraftperformance.org/mustang/p-51-dive27.jpg)

Title: Re: P-51 Airfoil and Turn Performance
Post by: FLS on December 10, 2014, 02:59:51 PM
Thanks for translating and posting. Your site is a great resource.