Draining E in turns

[gripen]

Originally posted by Badboy
Even though it is a function of aspect ratio, sweepback angle, taper ratio and twist, the largest influence on the wing of a WWII fighter with very little sweep or twist comes from aspect ratio and taper ratio and so there are approximate formulae for estimating e that only include aspect and taper ratio, and even more approximate methods that only include aspect ratio. The important thing you must appreciate is that they are only approximate. But better than just assuming a constant value for every aircraft.

Hope that helps...

Badboy

Edit:

Just checked my own teaching notes, and should add that the Oswald efficiency factor is also a function of wing camber and Mach number. In any case, calculating the Oswald efficiency factor from wing geometry is problematic. The values obtained are generally only valid for low AoA work because the calculations require that the flow remains fully attached, whereas in practice that is rarely the case. Generally such methods produce optimistic results.

Zigrat's spread sheet gives e factors:

Spitfire: 0,878
Fw 190: 0,865

If compared to the Lednicer's chart, the difference seems to be quite low, the Spitfire being much closer elliptical lift distribution than the Fw 190. Maybe adding taper ratio to the calculation would give better estimate. Anyway, e factor itself is not directly related to the aspect ratio, maybe adding taper ratio to the calculation would help.

Originally posted by Crumpp
Your correct and I changed it.  Raises the speed to 310mph were the FW-190 gains advantage over the Spitfire in drag.

Hm... Well the JF275 at 4500 ft has advantage in drag over the Fw 190A-8 at all speeds. And in the turning performance even the JL165 has advantage at all speeds.

Originally posted by Crumpp
No way around it, even with your values the FW-190 produced less parasitic drag than the spitfire.

Well, the flat plate areas for Cd0 are:

Fw 190A-8: 4,82
JL165: 5,18
JF275: 4,77

So according to my numbers the JF 275 has lower parasitic drag than the Fw 190 (filled and polished).

Originally posted by Crumpp
Seems to me that the FW-190 has the same amount of braking forces applied to a lot more inertia.

Well, I have allready calculated forward acceleration above with the mass of the planes.

Originally posted by Crumpp
3.  1770PS is at full throttle height and the FW-190 is not at full throttle height but rather just below it.  
I will check the chart again but 13000 feet is 3.96 Km and not 5 Km which is roughly the full throttle height of the BMW-801D2 RAM at 1.42ata @ 2700U/min.

I can't read the chart more accurate, 1770 ps seem to be quite exact value for the 4500 ft.
 

Originally posted by Crumpp
Yes, actually that was a quite common practice for both Axis and Allied.  There is one story of a 109 pilot who crashed twice in one week.  His crew chief refused to polish anymore planes for him to he could prove he would not crash them.

Well, if we want comparable results, the Spitfires should have been filled and polished too.

Originally posted by Crumpp
I have at least 3 flight graphs for the FW-190A8.  All of them are within a few miles per hour, one is faster, the other two are the same.  This graph is about average.

Well, the Navy Fw 190 performed quite close to your numbers near sea level given the polishing and filling. Still I don't see evidence that your numbers are flight tested.

Originally posted by Crumpp
However, since I have already done the Merlin 61 vs FW-190A5, I am pretty sure the results will be pretty close.

Well, you are producing enermous amount of numbers and I have no time to check them all (it could be a good idea to limit values to the only relevant part), but couple things should be noted:

Why should the Fw 190A-5 be so much faster than the Navy 190 and the Fw 190A-8 with same power settings?

Are the Fw 190A-5 values really flight tested?

The wartime documentation gives 1520 hp at 1st FTH and 1300 hp at 2nd FTH for the Merlin 61.

gripen

[Charge]

"Fw 190 (filled and polished)"

What?

-C+

[Crumpp]

"Fw 190 (filled and polished)"

They waxed it.

Crumpp

[Crumpp]

Why should the Fw 190A-5 be so much faster than the Navy 190 and the Fw 190A-8 with same power settings?

I don't think it is, Gripen.  The best climb speeds line up perfrectly.  Not so sure on the level speed I will have to check it out again.  Probably not since the Navy was having so much trouble out of the BMW using US AVGAS.

Crumpp

[Crumpp]

Here are the results with Gripens changes.
Gripen Can I please get a copy of the Merlin 66 Horsepower chart you are looking at.

Both Horsepower figures are RAM in order to line up the numbers for comparision.

FW-190A8
1.42ata @ 2700U/min
Step A - Enter Aircraft dimension Data
Wing area S (sq. feet) - 196.96
Airplane weight, lbs (as tested) - 9418
Wing span, ft - 34.45
   
Step B - performance #s at a known altitude
    
    
Altitude (feet) - 4500
Maximum speed (at test alt.- mph) - 356
Engine Horsepower (bhp at test alt) - 1730
Stall speed (mph, at test alt) - 110


speed (mph TAS)
300

speed (fps)
440

CL
0.237567

D(p)
926.7646

D(i)
136.9862

CL^2
0.056438

CD(tot)
0.026833

Drag (tot)
1063.7508

thrust (lb)
1617.469

excess power (bhp)
621.1324

P.E.
0.779137

Spitfire Mk IX Merlin 66 (+25)


Step A - Enter Aircraft dimension Data
Wing area S (sq. feet) - 242
Airplane weight, lbs (as tested) - 7400
Wing span, ft - 36.1
   
Step B - performance #s at a known altitude
    
    
Altitude (feet) - 4500
Maximum speed (at test alt.- mph) - 366
Engine Horsepower (bhp at test alt) - 2050
Stall speed (mph, at test alt) - 90



speed (mph TAS)
300

speed (fps)
440

CL
0.151922

D(p)
1051.797

D(i)
75.20623

CL^2
0.02308

CD(tot)
0.023137

Drag (tot)
1127.0037

thrust (lb)
1996.538

excess power (bhp)
869.5343
P.E.
0.779137

[Charge]

Waxing is not filling. Waxing = polishing.

Polishing was even done in operational units but AFAIK filling was only done on some experimental and speed record a/c.

-C+

[Crumpp]

Polishing was even done in operational units but AFAIK filling was only done on some experimental and speed record a/c.

I am afraid there is plenty of anecdotal evidence showing otherwise.  

Both filling and polishing are simple task's that any crew chief on both sides not only could but did do often.

One of the USAAF P47 Aces was famous for flying a filled and polished Jug.  His crew chief skill at it was the envy of the other pilots in the squadron.

You can see the above thread for the 109 pilot anecdote.

I fail to understand the double standard being applied here. We want to use only the best available data for the Spitfire but when the results don't turn out how we expect then that data is not good enough.

1.  Folks want me to apply data from experimental a/c for the Spitfire because the data listed as the actual Merlin 66 (+25) performance is not good enough.

2.  Folks want to complain at the same time over a wax job on the LW A/C.

3.  I am using the best available data I have and applying the same standard to both A/C.  Playing favourites is totally contrary to what I want to accomplish.

Both Horsepower figures are RAM in order to line up the numbers for comparision.

Darn it.  Gripen I posted the wrong one.  I did the calculations with your Horsepower figures for both Aircraft.

It brought the total drag of the Aircraft within 1 pound of each other, in the FW's favour, at 300mph.  By 315mph the drag had moved almost 100lbs in the FW-190's favour.

I will post the new results when I get back from work.

Crumpp

[Angus]

From Crumpp
"With the 190's lower parasitic drag and greater inertia it's easy to see why there is so much anecdotal evidence that Merlin Power Spits never took on 190A's in the vertical. "

You are referring to E-to-zoom at high speeds I presume.

I'll post a nice anecdotal evidence of what happened if the 190 had a knife fight with a Spitty and let it's speed go to far down.
(1 Spit IX vs a gaggle of 190's)
I'll try to find out from other sources which IX, and given the date and location your sources might be able to find out about the 190's

It will be an hour or two. Hope I got y0u all drooling

[gripen]

Originally posted by Crumpp
Not so sure on the level speed I will have to check it out again.

The data set in your source page gives about 20-30 km/h faster speeds at low altitudes than the A-8 data set and the Navy data set.

Originally posted by Crumpp
Probably not since the Navy was having so much trouble out of the BMW using US AVGAS.

Well, if you have evidence on that, please post. Otherwise that is purely speculation. Besides performance numbers are quite close to Fw 190A-8 so the engine probably run fine.

Originally posted by Crumpp
I fail to understand the double standard being applied here. We want to use only the best available data for the Spitfire but when the results don't turn out how we expect then that data is not good enough.

Well, you truly fail to understand that the JF275 had lower drag at all conditions than the Fw 190A-8 despite the Fw was specially prepared (if the Fw was really tested).

Originally posted by Crumpp
1.  Folks want me to apply data from experimental a/c for the Spitfire because the data listed as the actual Merlin 66 (+25) performance is not good enough.

The JF275 was a standard Spitfire VIII while the Fw 190A-8 you use was not (if the Fw data is actually tested).

Originally posted by Crumpp
2.  Folks want to complain at the same time over a wax job on the LW A/C.

No one complains about wax job but if you want fair comparison between two aircraft, the surface finish should be similar. However, the JF275 did better even without special finish.

Originally posted by Crumpp
3.  I am using the best available data I have and applying the same standard to both A/C.  Playing favourites is totally contrary to what I want to accomplish.

Well, the evidence above speaks for something else.

Originally posted by Crumpp
It brought the total drag of the Aircraft within 1 pound of each other, in the FW's favour, at 300mph. By 315mph the drag had moved almost 100lbs in the FW-190's favour.

Well, the JF275 had lower flat plate area for Cd0 than your Fw 190A-8. In practice it means that the JF275 had lower drag at all speeds as well as at all reachable g loads.

gripen

[Crumpp]

The data set in your source page gives about 20-30 km/h faster speeds at low altitudes than the A-8 data set and the Navy data set.

No that performance graph EXACTLY matches the Focke-Wulf comparison flight test's conducted for the Ta-152 development program.  In fact, it is an English translation of the same test and a poor one at that.

The German text describing the condition of the planes reads, "Surface fixed and painted" on the FW-190A8.  It was  flown to establish performance improvements against 4 different prototypes over several months.  It says absolutely NOTHING about "filled and polished".  

It means just what it says.  Needed repairs were made and the plane was repainted.  Totally different from "filled and polished".

I would be glad to provide the graph page from the report so you can evaluate it yourself.  In fact I will email it to Hitech.

Well, if you have evidence on that, please post. Otherwise that is purely speculation. Besides performance numbers are quite close to FW 190A-8 so the engine probably run fine.

Unless you have different report, the US Navy test was an FW-190A5 NOT an FW-190A8.

It was the tactical trials of a crash-landed and repaired FW-190A5/U4.  The FW-190A5/U4 was later blanket redesignated the FW-190G1.  The aircraft needed extensive repairs to both the airframe and the engine before being flown against an F4U and Hellcat.

The engine quit on three attempts to reach service ceiling, which was never reached in the Navy test and at low rpms fouled the plugs consistently.  In other words it was not running right.  My guess is it did not like the US AVGAS that had a lower aromatic content than the German aviation fuels.  If you want to try an experiment with different fuels, just put some MOGAS in your car and see how it runs.  The information is listed on Page 4 of the report.  I can provide you with a copy of it if you like.

Besides performance numbers are quite close to FW 190A-8 so the engine probably run fine.

If your refering to the level speeds then NO they are not close at all.  If you are refering to the horsepower development chart on page 5 then you are correct.  Those numbers are a reprint taken from the FW-190A5 pilots manual as are the dive restrictions.

Crumpp

[Crumpp]

Well, the JF275

Please provide a link on the performance data for JF275 or an actual report.  I cannot any data on it nor is it listed on this site:

http://www.fourthfightergroup.com/eagles/spittest.html

Crumpp

[Nashwan]

JF 275 data is at http://www.fourthfightergroup.com/eagles/spit8.html

[Crumpp]

You sure you want this version?

Manoeuvrability

5......... There was nothing to choose between either aircraft as regards turning circles at any height; whether on offensive or defensive manoeuvres neither could make any impression on the other. In rate of roll, however, the Spitfire IX was considerably better especially at low altitude. A number of full rolls through 360 degrees were timed by the same pilot flying each aircraft in turn and although quanitative tests are difficult to produce, it appeared that there was often more than 1.5 seconds superiority for the Mark IX over the Mark VIII. The Mark VIII feels fairly light on the ailerons but at high speeds it becomes very heavy, and so this new combination of extended wing and small aileron cannot be considered satisfactory.

Looks like it is outstanding at high altitudes but much worse at lower altitudes than even the Merlin 61.

 http://www.fourthfightergroup.com/eagles/jf934level.jpg

I will run the numbers but a quick glance leaves me skeptical on the performance improvement.

There is no chart either for JF275, only a table with no documents to back it up.  I will run both the tested data and the table data.

I need the wing area as it has an extended wing and a source.

Thanks!

Crumpp

[Crumpp]

FW-190A8 at 1.42ata@2700U/min

Gripen's Horsepower rating for the BMW-801D2 is only 10 hp away from the full throttle height horsepower rating at over a 600 ft. below full throttle height.  Using a straight edge on the chart IMO 1730 is more accurate.

Step A - Enter Aircraft dimension Data
Wing area S (sq. feet) - 196.96
Airplane weight, lbs (as tested) - 9418
Wing span, ft - 34.45
   
Step B - performance #s at a known altitude
    
    
Altitude (feet) - 4500
Maximum speed (at test alt.- mph) - 356
Engine Horsepower (bhp at test alt) - 1745
Stall speed (mph, at test alt) - 110

speed (mph TAS)
300

speed (fps)
440

CL
0.237567

D(p)
935.3667

D(i)
136.9862

CL^2
0.056438

CD(tot)
0.02705

Drag (tot)
1072.3529   @310mph - 1127.045  @315mph - 1155.4773

thrust (lb)
1699.492

excess power (bhp)
627.1391

P.E.
0.779137

Spitfire Mk IX Merlin 66 (+25)

Using the horsepower rating Gripen provided.  It would be nice to have full disclosure and receive a copy of this chart.

Step A - Enter Aircraft dimension Data
Wing area S (sq. feet) - 242
Airplane weight, lbs (as tested) - 7400
Wing span, ft - 36.1
   
Step B - performance #s at a known altitude
    
    
Altitude (feet) - 4500
Maximum speed (at test alt.- mph) - 366
Engine Horsepower (bhp at test alt) - 1945
Stall speed (mph, at test alt) - 90


speed (mph TAS)
300

speed (fps)
440

CL
0.151922

D(p)
996.2789

D(i)
75.20623

CL^2
0.02308

CD(tot)
0.021998

Drag (tot)
1071.4852  @ 310mph - 1134.2264  @ 315mph - 1166.5965

thrust (lb)
1894.276

excess power (bhp)
822.7911

P.E.
0.779137


The faster you go the more the total drag swings in the FW-190A's favor.  The parasitic drag always favors the FW-190.  

Also seems to me that the FW-190 also has less braking forces per mass acting on it.

So I would say David Lednicer's conclusions were correct.

Crumpp

[Crumpp]

My guess is JF275 was one of the Spitfire Mk VIII's with a standard wing.

http://www.fourthfightergroup.com/eagles/spit8.html

AND

Two interesting modifications were tried on individual Mk VIII's: the first was a six-bladed, contra-rotating propeller; the second was a teardrop canopy to improve the pilot's rearward view. Both these features were adopted as standard on later production variants.

http://www.btinternet.com/~lee_mail/spitfire2.html

Too bad:

In many ways the Mk VIII was the best of the Spitfires, but as it never saw service in Northern Europe, its capabilities largely went unrecognized.

I will run the numbers and see what is up with the MK VIII.  This is the version I think Guppy's friend flew.  I hope HTC decides to model it.  It would have it's place in ToD IMO.

Anybody have the wing area with the extensions on it?

Crumpp