Pyro, P-47D Performance Not Matching Charts

[funked]

Frenchy didn't pick a real good title for his thread:  http://bbs.hitechcreations.com/smf/Smileys/default/Forum9/HTML/000849.html

Looks like this disease is spreading to many AH planes!

[SFRT - Frenchy]

watching and learning from Funked.  

[Fishu]

I knew there was something wrong with P-47  

[Pyro]

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

[SFRT - Frenchy]

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?

[Vermillion]

Yes Frenchy, its quite common to gain around 5mph with WEP for the majority of aircraft.

------------------
Vermillion
**MOL**, Men of Leisure

[-duma-]

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)

[SFRT - Frenchy]

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.
====
at 5k
HTC Chart 346 (Wep Off) -- 360 (Wep on)
flight 345 (Wep off) -- 350 (Wep on)
===

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   (and when HTC will give me the late war 56th marking, I will die even happier  ).


[This message has been edited by SFRT - Frenchy (edited 10-04-2000).]

[F4UDOA]

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

[funked]

The extra 350 hp probably helps the Jug too.  

[wells]

Exactly Funk,

The P-47 should gain more than 5 mph with 600 more horses, right?

[Fishu]

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.

[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.

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

[Karnak]

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

[F4UDOA]

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