F4UDOA, F4U-4 AH Testing info

[whels]

well while watching NFL today i decided  to test the F4U-4 for F4UDOA to compair to his Chart data.

interesting note, speed difference between 25% fuel and 100%
fuel is very small, which i think should be alot bigger diff, gain of maybe 1 to 2 mph at most. maybe fuel weight is not factored
in AH like it should, or atleast on F4U-4.

gained more speed between 100% ammo and 0% ammo,
on avg 5mph.

Testing was done offline mode, with 0 wind, minda map, fuel
burn set to 0, ammo and no ammo, wep and no wep, 25% fuel
and 100% fuel.   i would climb to test alt, drop speed below chart speed shown by 10 or so mph then engage 100% throttle and let
fly level till speed showed no more gain. wep test was done  with leaving wep on and taking speed just before Temp was hot enough to drop wep off.  same  routine was used for all 3 alts.


F4U-4

Fuel             25%               25%                  100%          100%
Alt                speed             speed               speed         speed
                 with ammo       no ammo           ammo         no ammo
------------------------------------------------------------------------------
500  
no wep           353               357                    352              353
wep                375               376                    375              375

20k
no wep           410                415                   405               410
wep                427                429                   426               426

26.2k
no wep            417                423                  412               417
wep                 430                435                  428               430

so compairing these speeds with ur charts F4U-4 is correct
on deck speeds but as alt goes up, the #s become slower then
chart shows, and fuel weight being light or heavy does not
seem to have very much affect on speed when i should.


Whels

[Badboy]

Originally posted by whels

interesting note, speed difference between 25% fuel and 100%
fuel is very small, which i think should be alot bigger diff, gain of maybe 1 to 2 mph at most. maybe fuel weight is not factored
in AH like it should, or atleast on F4U-4.

That difference is just about what you would expect. I just checked it out mathematically and for a difference in weight reflected by the difference between 25% and 100% internal fuel the difference in top speed was close to 3mph. The maximum difference I could get, by going from 1% fuel and no ammo, to 100% and a full ammo load, was only 5mph.

Hope that helps.

Badboy

[funkedup]

Weight should have very little effect on top speed.  The amount of extra lift needed to carry the fuel causes only a very small increase in induced drag at those speeds.

[Regurge]

At high speeds most of the drag is from profile drag, which doesnt depend on lift correct? If thats true I may have actually learned something useful from this BBS

[whels]

Originally posted by Badboy


That difference is just about what you would expect. I just checked it out mathematically and for a difference in weight reflected by the difference between 25% and 100% internal fuel the difference in top speed was close to 3mph. The maximum difference I could get, by going from 1% fuel and no ammo, to 100% and a full ammo load, was only 5mph.

Hope that helps.

Badboy

but why more speed gain from  ammo to no ammo, then
100% fuel to 25  fuel. does the 2400 rounds of 50cal weight
that much more then 250 gallons of fuel?

wish we had digital speed idicator to use off line, would make
taking speed changes more accurate.

id though that with so much less fuel, a much more speed gain would have came up with the much better HP/lbs  ratio.

whels

[Badboy]

Originally posted by whels


but why more speed gain from  ammo to no ammo, then
100% fuel to 25  fuel. does the 2400 rounds of 50cal weight
that much more then 250 gallons of fuel?

wish we had digital speed idicator to use off line, would make
taking speed changes more accurate.

id though that with so much less fuel, a much more speed gain would have came up with the much better HP/lbs  ratio.

whels

The amount of internal fuel you are talking about would be about six times heavier than the amount of ammo you mentioned, my guess is that you have some experimental errors creeping in.

Badboy

[whels]

Originally posted by Badboy


The amount of internal fuel you are talking about would be about six times heavier than the amount of ammo you mentioned, my guess is that you have some experimental errors creeping in.

Badboy

well speeds were taken from level flight at the alts listed. no
diving to gain speed. all speeds start below target speed. so what ever it gained was from level flight and what the plane
could do its self without help from dive or wind.

whels

[fats]

whels,

you coulda used the .speed XXX command and then engaged the speed trim and see if would climb or dive.


// fats

[Tyro48]

The specific gravity for fuel is about 6 lbs / gallon

faster ya go the more parasitic drag ya get

ye olde trade offs in action

[F4UDOA]

Heya Whels,

Picked this one up a little late.

Anyway I have doen almost the same testing with the -4 offline. Where the weight really makes a differance is in climb. All A/C in AH have a significant increase in performance in climb with each 25% reduction in fuel. I don't expect much of an increase in speed HOWEVER

Your speed checks are right on. Problem is at 20K the F4U-4 is to slow compared to the charts that Pyro has posted. The charts are directly from AHT(America's Hundred Thousand).  In the text included in those charts it states a top speed of 380MPH at sea level and 445MPH at 25K. At 20K no speed is listed but it looks very close to 440MPH again almost 20MPH to slow.

I haven't been complaining because at least we have the F4U-4 while there is no P-47M or Spit XIV. However when I do fly the -4 against the likes of these A/C and the Dora I would like it to have it's historic capabilty.

The current AH charts are somewhat conservative and I have never seen the originals to know exactly what the speed is supposed to be. Maybe Pyro has them but they seem a little low compared to what I have seen.

Here are the charts I would like to see for the F4U-4 in AH.