the not so studly Mustang

[Vermillion]

Well, I hadn't flown the Pony since the early days of the beta, so I took her out for quite a few spins over the weekend to see if I agreed that she was a broken down nag, or a fine quarterhorse filly.

And before anyone asks, I flew it in a very reserved classical BnZ style, with plenty of patience  

I pretty much only saw one place that I thought the Pony was deficient, and that was in Acceleration. The P-51 was extremely slow in getting up too speed, and I often had to dump much more alt than I would normally expect to get up a full head of steam. This allowed much slower planes to run me down occaisonally, primarily the Spitfire, and not the 109 that the people above had more trouble with.

I did quite a bit of reading on acceleration and drag, primarily in Americans Hundred Thousand. From the data presented there, I feel that the Pony in AH is not quite right, most likely in the acceleration/parasitic drag department.

FYI the P-51 was #3 in acceleration of all American Fighters, behind the P-63 KingCobra and the P-39 AirCobra. So if AH is correct (which is possible) the other American Iron is gonna be in a hell of alot of trouble.

One quote (taken from my memory) that interested me the most, was that in a purely vertical dive (90 degree's) it shouldn't take more than a few thousand feet for most american fighters to reach their posted dive speed limits (500 IAS for the P-51).  In some very unscientific testing I performed, I didn't see anywhere close to this kind of acceleration.

Right now I am looking at the data and trying to figure out some more scientific methods to confirm what I am getting at. More on this later.

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Vermillion
WB's: (verm--), **MOL**, Men of Leisure,

[Mark Luper]

I have done a lot of flying in the 51 since reading this thread. The times I had flown it before this thread I had been "caught" by primarily the 109 and to a much lesser degree the Spit and LA-5.

The post by Hristo (a terrific 109 pilot and a gentelman to boot) pointed out to me some of the things I was doing wrong. I was flying it like a WB runstang and it doesn't work that way here.

Since then I have been able to outrun every 109 that chased me except one and a barrel roll saved me on that one. I did manage to survive the encounter. He (don't know who it was) had gone into a a shallow dive to pick up some speed and I was just flying level with wep on. He managed to get close enough to start firing and my barrel roll managed to avoid the bullets. I still had good control at near 400 indicated and he didn't which gave me the opportunity to go into a shallow dive and pull away while he was recovering.

What I have done to insure my ability to leave the area when it got too hot is to start from a field at least 2 sectors from the action and climb to at least 20+k alt. Since I normaly fly for the Knights this is not hard to do :-).

Most of the time I climb to 25k or a bit higher. I will carry drop tanks and cruise an area I feel will give me an opportunity to drop in on an unsuspecting con. I have given myself a hard deck of 10k so that I can maintain enough alt to make a shallow dive when other non friendlies show up.

Flying this way takes a lot of patience and is time consuming and some may call me a bit of a coward when I don't engage more than one at a time, but I have been able to land most of my sorties this way and in time perhaps I can also increase my kill score too. I don't get many this way, normally a single and an assist, but I survive.

You also can't wait too long to start your getaway, if that 109 is within 1k your goose will probably be cooked in short order because he can outaccelerate you. I can get up to 500 indicated pretty quick, but not as quick as the 109 gets to its 400.

Straight and level, on autolevel with WEP on I can maintain what appears to be about 385 to 390 indicated after dropping down to the deck in a high speed shallow dive.

It's interesting when you start pretending you real life is in jepardy, makes for a much more satisfying game for me.


MarkAT

[funked]

Vermillion just remember three things:

1.  The AHT acceleration stuff is all calculated - not flight test data.

2.  It was calculated at a fairly high speed - 250 IAS.  A fast but heavy plane like the P-51 will do better here than at low speed.  The power to overcome drag scales with the cube of speed.  As you go to lower and lower speeds the ammount of power available to accelerate the plane becomes much larger.  So at 150 (for example) the importance of thrust:weight ratio is far higher than the importance of thrust:drag ratio.  If the calcs in AHT were done at 150mph instead of 250, the results would be much different.

3.  The U.S. fighters do not compare well at all to the Me 109 or the Spitfire in thrust:weight ratio.  So even though the P-51 is the 3rd best of the planes in AHT, including the foreign planes in the same analysis would put the P-51 well down the list.

[aircat]

 I'm sure theres info out there to acceleration rates to the differant speed... like 0 to take off speed then TO speed to 175 0-200 0-225 0-250 ect ect ect. if we can get the data then we can create a performance curve for available power/thrust to drag/wieght ratio.

[Vermillion]

Funked, Aircat:

Check in the different sections of AHT, the initial sections on acceleration & drag, and then the later chapters on the P-51 itself, and the last one on performance. Its in different tables, graphs, and bits and pieces, but I think the data is all there (at least for the P-51).

And according to the references AHT sites, its actual NACA flight test performance data, not calculated data.

Thrust is fairly easy to calculate as a function of horsepower and propellor efficency (AHT assume's 80% in example calculations, but Wells tells me that its a function of IAS).

Parasitic drag or zero-lift drag can be calculated with the the drag coefficent Cdo (constant listed in AHT and other sources), total wing area (constant), and the drag coefficent correction factor (function of %mach limit vs alt, which is given in AHT as a graph). FYI the only drag correction factor charts I have ever seen are for the P-51 and the P-38 in AHT, while drag coefficents themselves are somewhat easier to come by, but not easy.

However I haven't figured out how to calculate induced drag. AHT gives an example calculation of the relationship between parasitic drag/induced in relation to speed. BUT they don't give the equation used to calculate (or the variables, ie data, needed) the induced drag itself.

If someone can give me that equation, it would be quite simple to do a graph like aircat mentions in a spreadsheet, and then do controlled tests in the game to see if it is close.

Still looking for the induced drag calculations  

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Vermillion
WB's: (verm--), **MOL**, Men of Leisure,

[funked]

I'll check the AHT accel. table again, but as I recall it's all calculated.  And that prop efficiency is a pretty large question mark.

I agree that you can do some good calculations though.  I spent some time working up a spreadsheet to explain how a Yak-3 could easily stay with a P-51D for several miles after a dogfight.  I didn't take induced drag into account, but it won't matter much unless the planes have a drastically different wingloading or lift coefficients.  And I fudged the prop efficiency.

To do it right, you need the drag (both flavors) and lift coefficients.
And the variation in propeller efficiency with airspeed is not negligible.  I'm not sure how WB or AH treats this.

If you want to do a spreadsheet, contact Wells for help.  I know he has already worked out lift and drag for WB planes c. version 2.01.

Once you get it set up, run it at 250 IAS and you'll see the P-51D getting edged by most of the axis planes from the same period of the war.

But a real eye opener is to run it at 150 IAS.  At that speed the drag is not nearly as important as the weight, and the light planes really scoot away.  Often they can gain enough advantage between 150 and 250 IAS to stay ahead for quite a long while.

[This message has been edited by funked (edited 10-26-1999).]

[funked]

P.S.  Alternately you can kinda do what Aircat said.  Collect Speed vs. Time data for the AH planes and check for power/weight and power/drag ratios.  But again you have the unknown prop efficiency and two drag coefficients to deal with.  If you are serious about it, talk to Wells, he's the masta.  

[Pyro]

Verm:

Check the numbers themselves, not the rank.  Dean lists the acceleration under the stated criteria at 3.85 Ft/Sec/Sec.  Try that against the AH P-51 and I'm sure you'll find a similar result.  Keep in mind that as your velocity increases, your acceleration decreases due to thrust decreasing and drag increasing.  

BTW, if that figure was your car's acceleration rate at 0-60, it'd take you 23 seconds to get to 60mph.  It's not exactly the kind of acceleration that pins you back in your seat.



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Doug "Pyro" Balmos
HiTech Creations

[aircat]

.........

[This message has been edited by aircat (edited 10-26-1999).]

[Pyro]

Aircat:  Why are you posting this all over?  A single post would suffice, even better just a single link to Elevon.  Pasting huge amounts of text into a thread is not very nice to those who are reading it.  Doing it in multiple threads is downright rude.



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Doug "Pyro" Balmos
HiTech Creations

[aircat]

sorry didnt notice it was in multipul threads. I open up to 6 threads at once so one Im reading and the others are loading. and I minimzed one window after hitting submit and brought up a different one and thought I hit the close like I often do. so copied and pasted into wrong room. as for not just giving the link few ever go and read something at another sight.

(now why is I get yelled at for multipule threads when Ive seen other POST multiple threads and also there are others that write 10 times this much, not trying to start arguement but why yell at one and let others pass?)

[aircat]

scratch last post I'll just edit the posts.

[funked]

Aircat you're askin' for it...  

BTW the 4-gun P-51D loadout is mentioned in America's Hundred Thousand and some other sources as well.   Even if it wasn't "official" it was the kind of thing your crew chief could do for you.

[Vermillion]

Thanks for all the answers and help guys. I am just an engineer (who sometimes gets obsessed on a technical issue) that is trying to find out and learn all he can, sorry its in the blood  

Pyro: I appreciate the equations and info   I wasn't trying to imply you were wrong, merely looking for data that would support or disprove, my opinon and feelings on the FM's.  You always ask for hard data don't you  

Funked: In AHT, check out pages 112-113, specifically Graph 12 - "Drag Coefficent Correction with Mach Number for P-51D" and Table 6 "Fighter Drag Data". These are referenced to North American Report NA-46-130, 2/6/46.  See also page 377, under References, several listed are pertinent to drag coefficents and acceleration, and are NACA and North American reports. Also see pages 592-593, on Profile Drag Coefficent Summary and Drag Coefficent Rise with Mach Numbers (referenced at end of chapter). And lastly pages 603-604, concerning Comparison of Level Flight Acceleration Capability (and see end of chapter for references)

Now to just track down some of these reports on the NACA Technical Reports Server  http://naca.larc.nasa.gov/

Or maybe we could just convince Francis Dean to write the equivalent of AHT for the British, the Germans, the Japanese, the Russians, and if he has a little spare time the Italians and French  

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Vermillion
WB's: (verm--), **MOL**, Men of Leisure,

[Kraut]

Hehe!!! Many a newbie has come to grief, me included, by thinking the Pony was a super kite. In the hands of an experten it's deadly but in newbies', powder puff. My first, & still, flights/combats are "experiences" with grave outcomes for me mit this Allied Iron. It has a lot of good stuff but on AH or WBs, it doesn't have numerical superiorty & I "think" there in lies "some" of the mystery when comparing to actual real life data.
FWIW,
Good Hunting!