Pyro, P-47D Performance Not Matching Charts

[wells]

F4u,

The F4u-4 in that Navy test was using 115 grade fuel and was putting out more than 2400 hp, probably 2800 as most later R-2800's did.

[F4UDOA]

Wells,

Interesting point. But the test was done with the R2800-18W max rated 2400HP with BHP listed as 2100HP. The later R2800-42W may have put out more but I don't think the -18 did.

Do you think 115 Octane is too high? I have heard some of these Spit XIV tested at 125 and the same for the FW-190's using some high octane mixture. The NIK2 also benifited from high octane fuel in testing as well as the KI-84 also testing with120+ octane fuel.
115 seems almost moderate.

Why do you think the P-47 gains so much in climb and so little in speed? And the reverse for the F4U-1? I gave my theory, what's yours?

F4UDOA

[juzz]

 

The P-47 by contrast increased it's performance at the D25 model with the change of prop. It had the same engine power as the D22 but climbed nearly 1000FPM better at the same rated HP of 2300HP with just a prop change.

~1000fpm? Care to source that? Because the D-25 climb is listed as 2780fpm initial here, which means an pre D-22 model would climb at under 1800fpm? Hmmm... That site claims a 400fpm improvement btw.

[wells]

DOA,

115 grade is a very significant increase.  It allows higher boost pressures and therefore more power to be produced.  It's also called a 'performance number' when it's above 100.  Take that 2400 hp WEP figure and multiply it by 1.15

[funked]

FYI the 190's in AH conform with test data for 100 octane fuel.

[F4UDOA]

Wells and Funked,

That still doesn't explain the dramatic increase in climb between the F4U-1D and
F4U-4. Taking your theory Wells and reducing the climb rate of the F4U-4 by 15% brings it down from 4800FPM to 4080FPM at 2400HP. The F4U-1D put out 2250HP 150HP less than the
-4 or 6.25% less. So in theory it should climb roughly 6.25% less than the -4 right?
Which is 3825FPM (Wells that number is exactly what your climb calculation put the F4U at BTW). So we know the F4U-1D didn't climb that well. So my question is why the great disparity in climb with only a 150HP difference?

Juzz, Wells, Funked,

My original question is why the difference in performance between the P-47D-20 and D25 when both have Water and 2300HP. Juzz, I exagerated the numbers because I wasn't looking at my book at the time.
The P-47D20 climbed at combat power at 2750FPM. The same rated engine in the
P-47D22 climbed at approx 3350FPM a difference of 650FPM. Not 1K but still rather significant. Even at 400FPM the prop change would have caused a significant improvement.

I think the two A/C benifited from the same improvement. The problem I have is that I can't find any record of the change in flight characteristics change for the F4U. Again this is not an AH related topic but an interesting point to ponder.

Thanks F4UDOA

[This message has been edited by F4UDOA (edited 10-05-2000).]

[SFRT - Frenchy]

-----------------
From pyro:
Frenchy, I think you misunderstood me. I'm saying that it is doing what is graphed on the webpage. I only offered some explanations as to why your test did not match.
-----------------

Dear Pyro, I'm sorry to intrude again, but I did the tests like you advised me to do. I hope I'm not missunderstanding you again.

I took a P47-D30, 25% of fuel, full amo, 2 DT. I climbed to 5K, shot all the amo to have 0 amo left, droped the DT's and accelerated to max lvl speed. Then I put the Wep on and recorded the top speed.

From this test, i got same results as when I did it with 100% fuel, full amo?!?!? I'm confused now...

5K, Wep Off (320 MIAS, 345 MTAS)
    Wep On  (330 MIAS, 352 MTAS)

I'm still 10 MPH short of your chart and Wep gives me a additional speed of 7 MPH only, not the 14 MPH stated by HTC chart.

You did the test yourself and it matched your datas, do you think I have a problem with my PC? Does anyone else would be kind enought to perform the test above and to let me know what data he found?

Pyro, do you wish me to send you a video of this tets?

Thank you to take the time to clear this up with me, it's very kind of you.

Be safe all  

[wells]

Pyro, I think Frenchy is right.  The D-30 isn't putting out 2600 hp for combat, so it seems.  Climb and speed is indicative of only 2300 hp, even though the gauge would lead one to think that you were getting 2600 hp.  Speed increase with WEP at 3000' was 10 mph (322 to 332 mph).

[wells]

DOA,

I don't know why the discrepency exists.  All I can say is we need to see the official Navy document on the test.  It might reveal that the engine simply wasn't putting out, much like the F6f-5 test revealed (combat power was only 30 hp more than rated MIL in that test).  

My calcs give the P-47D a MIL climb rate of 2800 fpm @ 14500 lbs and 3300 fpm with 2300 hp, which match AHT data pretty closely.  The same calcs for the F4u-1 (12000 lbs) give me 3400 fpm MIL and 4100 fpm (2250 hp).  For the F4u-4 at 12500 lbs, I get 4300 fpm (2450 hp), 3600 fpm MIL (2100 hp) and 4900 fpm with 2800 hp.  My calcs will probably overestimate climb rate a little bit as I am not accounting for any drag rise at lower speeds (other than induced), which I have no method to accurately predict, but in the cases of the P-47D and F4u-4, the overestimation is only about 100-200 fpm compared to flight test data.  I find it hard to believe that the propeller was that much less than optimal on the F4u-1/early P-47's, but perhaps it was, seeing as how new propellers were fitted!  After all, they never had to deal with power/props that size before!

[juzz]

If the D-30 is slower at 5k, at 30k things get worse.

P-47D-30; 8 guns(267rpg) and 100% fuel.

MIL - Chart: 418mph, AH: 410mph
WEP - Chart: 430mph, AH: 420mph

But the big difference is in the climbrate.

The chart:
 

In AH - with only 6 guns(267rpg) and 100% fuel, the P-47D-30 climbs at 3000fpm on WEP.

[niklas]

is it possible that those official charts are still from V1.03?
I remember myself that the 190 lost also a bit climb performance with V1.04 compared to V1.03

btw, when someone does a speed test: Donīt read the number from the the gauge. Set your climbspeed to a value what you think your speed is, than activate auto climb. when you begin a dive your climbspeed was too low, hit auto level again and decrease cs. If you begin a climb increase it. Try so long until you stay level in autoclimb than you got your indicated airspeed. this is imo the best way to measure my max. speed.
BTW, a 50MPH intervall (i.e 300 to 350mph) is interrupted by 3 little notches in the speed indicator, that means one notch = 12.5 MPH and not 10MPH right?

niklas

[juzz]

Ahh, but the Fw 190A-5 climb change was documented in the readme file...

Another sign that something is wrong is that the D-25 performs exactly the same with WEP as the D-30 - which is supposed to have several hundred more HP in WEP.

Thanks for the speed tip, I would never have thought of doing it that way!  

[Citabria]

P-47D30 climb 100% fuel 267 rds 8 guns no external ordnance.

AH 01k 3000fpm wep, 2400fpm (chart 3225fpm wep, 2440fpm)
AH 05k 2900fpm wep, 2400fpm (chart 3200fpm wep, 2450mph)
AH 10k 2750fpm wep, 2350fpm (chart 3150fpm wep, 2440fpm)
AH 15k 2600fpm wep, 2250fpm (chart 3000fpm wep, 2400fpm)
AH 20k 2450fpm wep, 2050fpm (chart 2800fpm wep, 2200fpm)
AH 25k 2050fpm wep, 1750fpm (chart 2400fpm wep, 1800fpm)
AH 30k 1500fpm wep, 1250fpm (chart 1700fpm wep, 1450fpm)


top speeds from a dive +50mph beyond max speed wep on then deceleration noted

450mph+ TAS dive decelerated to:
 
30k: 420mph wep, 410mph (chart 430mph wep, 417 mph)
26k: 420mph wep, 400mph (chart 430mph wep, 410mph)
20k: 398mph wep, 385mph (chart 412mph wep, 393mph)
15k: 385mph wep, 370mph (chart 388mph wep, 377mph)
10k: 370mph wep, 360mph (chart 377mph wep, 367mph)
05k: 350mph wep, 340mph (chart 360mph wep, 346mph)
01k: 346mph wep, 327mph (chart 346mph wep, 327mph)


[This message has been edited by Citabria (edited 10-09-2000).]