Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: funked on October 03, 2000, 07:02:00 PM
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Frenchy didn't pick a real good title for his thread: http://bbs.hitechcreations.com/smf/Smileys/default/Forum9/HTML/000849.html (http://bbs.hitechcreations.com/smf/Smileys/default/Forum9/HTML/000849.html)
Looks like this disease is spreading to many AH planes!
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watching and learning from Funked. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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I knew there was something wrong with P-47 (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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Took a look at it and didn't find anything out of whack. A couple things though, it takes forever to get a P-47 up to its max speed in level acceleration. 15000 lbs of inertia is a lot for that last hundred pounds of thrust to act on. Second thing is I notice is the gauge isn't exactly perfect, but it's better than the Spits. We are planning on redoing gauges sometime in the future- not the short term future, using a new method that will make more accurate gauges. Also the charts correspond to a normal gross weight with an ammo load of 267 rpg, so if you're in the overload condition, performance will suffer some.
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Doug "Pyro" Balmos
HiTech Creations
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Thank you for your efforts pyro, much appreciated. A take for granted that a 5 MPH increase when i turn Wep on is normal compared to other aircrafts?
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Yes Frenchy, its quite common to gain around 5mph with WEP for the majority of aircraft.
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Vermillion
**MOL**, Men of Leisure
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As a similar example, Tiffy gains 10mph heavy and 15mph clean with WEP, which is what you'd expect really. The main difference is acceleration. (20s difference accelerating from 160 - 360)
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Thanx you Vermillon,
I was just intrigued because HTC charts states an acceleration of 14 MPH while I was getting 5 MPH only. It's HTC charts who are wrong then.
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at 5k
HTC Chart 346 (Wep Off) -- 360 (Wep on)
flight 345 (Wep off) -- 350 (Wep on)
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Duma, thank you also for your feed back, turn, climb and acceleration is not my concern, I know it's an heavy bird.
I just thought the speed gain in level flight from "Max speed wep off" to "max speed wep on till it exausts" would be more than 5 MPH (at least like HTC charts 14 MPH).
Pyro said he checked it so I trust him. Maybe HTC will correct the charts for the P47-D30 to reflect the 5 MPH speed increase.
I will fly the Corsair now hehehe 20+ MPH increase at 5K when wep goes on Wohooo! humm... nope, I will stay and die in my P47 (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) (and when HTC will give me the late war 56th marking, I will die even happier (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)).
[This message has been edited by SFRT - Frenchy (edited 10-04-2000).]
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SFRT-Frenchy,
Hey, youn brought up an interesting subject about the difference in performance with WEP between the F4U-1 and P-47D30. You noted that the F4U gains almost 20MPH using WEP and the P-47 only gains 5MPH. Seems out of balance right? Look again at the climb stats for the two with WEP and you will see that the P-47 gains almost 800FPM in climb as opposed to the F4U which gains only 300FPM.
Seems like the speed and climb should go together right?
It seems odd to me that an A/C that is so much faster(F4U) at low alt climbs slower than the heavier A/C(P-47). I have a theory on why this is. I believe it is related to propeller performance. But unforntunately for me there is very little comparitive data available for the F4U.
Later
F4UDOA
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The extra 350 hp probably helps the Jug too. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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Exactly Funk,
The P-47 should gain more than 5 mph with 600 more horses, right?
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Many planes has this same problem that they gain perhaps 5mph from 100% to WEP.
Spit Mk.V is one and P-47 seems to be another.
There is more also.
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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.
F4U- That would be true if propeller efficiency was uniform between all speeds. Exhaust thrust is also a major difference between the two planes.
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Doug "Pyro" Balmos
HiTech Creations
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I remember reading a British report that estimated the power gain from exhaust thrust and about 20hp per stack. Gave the Spitfire MkXIV 120hp more power, according to the Brits.
Sisu
-Karnak
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Pyro,
Glad you tuned in. I am not disputing the AH FM in this one. But I do have a question or two for you on this topic.
The F4U has 350HP less than the P-47D30 at sea level. F4U-1D=2250HP P-47D-30=2600HP but the F4U is nearly 20MPH faster at sea level both using WEP. Must be drag and weight right? Don't the same factors apply to the Climb? Look again at the military power stats of both and the F4U is faster and climbs better. Only with WEP does the P-47 begin to climb nearly 800FPM better than Mil settings.
My theory is this. The propeller of the
P-47D-25 and later increased climb significantly and is documented quite well. The F4U-1D also had a propeller change mid production to a different blade design that also increased performance but is not documented anywhere as to what that increase was. But it is noted clearly to increase perfromance in the F4U pilots manual,
the P-51B vs F4U-1A test and the FW-190A5 vs F4U-1D test. But no mention of this change is in any performance chart I have ever seen unlike the P-47. It would also help explain the enormous increase in climb performance of the F4U-4 to 4800FPM at sea level with only 2400HP. The -4 used the same blade as the updated -1D except in a 4 blade design. The -4 weighed 500lbs more as well.
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. Unless the exhaust configuration also changed during this time I doubt this was responsable for the increase. Unless that version came equiped with the
Roger Ramjet turbo fun pack.
Later
F4UDOA
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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.
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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
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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 (http://home.att.net/~jbaugher1/p47_4.html), which means an pre D-22 model would climb at under 1800fpm? Hmmm... That site claims a 400fpm improvement btw.
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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
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FYI the 190's in AH conform with test data for 100 octane fuel.
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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).]
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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.
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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 (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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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).
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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!
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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:
(http://www.hitechcreations.com/images/charts/p47d30climb.gif)
In AH - with only 6 guns(267rpg) and 100% fuel, the P-47D-30 climbs at 3000fpm on WEP.
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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
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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! (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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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).]