View Full Version : Weird performance figures

05-20-2007, 02:08 PM
If you go to http://www.wwiiaircraftperformance.org/f4u/f4u.html and scroll down to the bottom, you'll find links to FAA Corsair performance.

F4U-1 FAA test, regular wing area, P&W R-2800-8

F4U-1A FAA test, regular wing area, P&W R-2800-8

Corsair II and III FAA test 1, clipped wings, P&W-R28008W

Corsair II and III FAA test 2, clipped wings, P&W-R28008W

Corsair Mk.IV FAA test, clipped wings, R-2800-8W

If you check out their top speeds, they vary drastically. Did British lower grade fuel kill performance this much? I'm guessing that the last 2 tests are performed with American grade fuel if that is so.

05-20-2007, 02:26 PM
Some tests have 2000Hp engine, some 2250HP, those are lebeled water injection, the weaker ones aren't.


05-20-2007, 03:02 PM
The 3rd test on the list has the 2,250 hp engine and the plane still performs poorly.

The difference between the R-2800-8 and the -8W was the Water injection, hence the 'W' suffix. This water/alcohol mix gave the engine an extra 250 hp which boosted top speed from 417 mph to 425 mph. Not from the sad 362 mph to the 405/415 mph seen in the tests.

05-20-2007, 03:59 PM
First we need to know if they flew with 100 % fuel after we need to know if they went to Crimea and then flew in good weather condition and at noon if none did the above regulation all real tests will be wrong!!! Be sure....


05-20-2007, 04:34 PM

05-20-2007, 04:34 PM
Devil lies in the details... be sure to check airframe conditions for external stores, bombracks, compressibility corrections, notes of poor surface quality, and amount of power the curve referes to..

Even then, it was accepted for WW2 serial production fighter aircraft to be +/- 3% slower or faster than the 'official' values given.

I'd say it's not strange if you find two different results for the same aircraft, it's strange when you find two similiar results ! http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

05-20-2007, 04:41 PM
This water/alcohol mix gave the engine an extra 250 hp which boosted top speed from 417 mph to 425 mph. Not from the sad 362 mph to the 405/415 mph seen in the tests.

I can see the difference in HP for the engines but then it says nowhere what max. speed is.
With or without injection. Is this mentioned elsewhere?

There are different wieghts from test to test as well. Is somewhere described which loadout/weight was used for which test?

Dunno either how they measured the speed.

Or maybe secretary couldn't read what was scribbled on note pad and made a mistake...

One thing for sure: it is extremly difficult to know what the top speeds of a certain plane was as there are so many variables in testing/measuring.

At the end of a day tests which do not describe the accurate testing procedure are not of much use.

At university we had to do some experiments to measure g and I can tell that there were huge differences in the results of each team (and even among the various test of the same team) - all using the same rig and testing procedure...


05-20-2007, 04:48 PM
The last two are in weight category (a) roughly 1000 lb lighter...


05-20-2007, 05:02 PM
Could it be that a unit conversion error has taken place?

If the "low" figures were actually knots rather than mph and the data sheets have been misprinted then they come back into line.

For example, 374 knots ~ 430 mph. Which seems reasonable


OTOH this would make the loiter speed on the data sheets rather high, so this may well not be the most plausible explanation.

05-20-2007, 05:12 PM
...meant HEAVIER...


05-20-2007, 05:18 PM
last 3 reports are of same date in 44, first two same date in 43. Maybe different loadouts/weights?


05-20-2007, 07:22 PM
That does seem to be a possiblility. Oh well, the FAA Corsairs seem to perform fine in this game. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif