Acceleration comparisons

[horseback]

Notes on USN/USMC Fighters tested @ 5K ft.

1. The early Wildcats seem to compare with what I know of their performance, not spectacular but stable; however, the FM-2, which was 500 lbs lighter & somewhat aerodynamically cleaner than the F4F-4, as well as enjoying a 160 hp power advantage at altitudes up to nearly 20,000 ft, is portrayed in-game as even more sluggish than its predecessors. I was so surprised by this, I ended up re-running the FM-2 to ensure that I hadn't left the landing gear hanging down or something, but it was just as sluggish and 'meh' as the first time. Historically, this was simply not the case. The FM-2 was widely acknowledged as the 'wilder' Wildcat; being lighter, cleaner and more powerful at low and medium altitudes, it had superior climb and acceleration, and a somewhat better top speed at low and medium altitudes. It was a much better match for the Zero, even the later models. Someone's got some 'splaining to do.

2. There is very little if any difference between the F4U-1/Corsair Mk I and the F4U-1A, which makes little sense, given the -1A's water injection and the fact that the runs made in the -1A were all much more level overall. The Dash 1A is ultimately faster once you reach 480 kph, but it should be no contest from the start. This just doesn't seem right. I also added the Dash 1D, and it has a noticeably better jump, but the same general top end.

3. Both models of Hellcat continue to be a huge letdown. With or without water injection, it is portrayed as a slug, and much slower than the official numbers I have found. A standard F6F-3 should be capable of 290 kts/330 mph true airspeed, or about 530 kph at this altitude. If the Wonder Woman 'speedometer' is correct, that would mean an IAS of about 470/480 kph in-game. The best level TAS I got from the F6F-3 was just over 510 kph, and the best level TAS on the F6F-5 was around 515 kph, or about 460 kph indicated for both. Again, there was very little difference in acceleration between the two, in spite of the extra 200 hp or so that the water injection of the Dash 5 is supposed to have. Again, I re-ran the Dash 5 to make sure that I hadn't done something wrong. The main difference is in top speed, but from 270 to 380 IAS indicated, there is no difference.

cheers

horseback

[JtD]

The problem with the F4F is twofold, first, the FM-2 appears to be indeed slightly undermodelled, and second, the F4F-3 and F4F-4 are modelled very generously, climb rates exceeding documented data in the region of 20%. This turn historical relations upside down.

Which charger gears were you using for the F6F and F4U?

[horseback]

Originally Posted by JtD

The problem with the F4F is twofold, first, the FM-2 appears to be indeed slightly undermodelled, and second, the F4F-3 and F4F-4 are modelled very generously, climb rates exceeding documented data in the region of 20%. This turn historical relations upside down.

Which charger gears were you using for the F6F and F4U?

I used the first stage (which should be analogous to 'Neutral' on the real things) blower for all the USN-USMC fighters; as I recall, the second stage shouldn't be engaged until about 8000 ft. Mixture was the standard 100%. While I have read that the superchargers had two gears for each stage, this doesn't seem to be modeled.

All of these aircraft seem to fall well short of generally accepted performance figures for speed at sea level and 5000 ft for military power (much less War Emergency Power), including the Wildcats, and the relationships seem a bit skewed. I would think that the Hellcat should initially be a good deal closer to the Corsair; the weight difference is not that great (with full internal fuel, some sources show the Corsair as the heavier of the two), they're using the same engines and drag shouldn't exert that great an influence until later in the speed range.

Interestingly, the top speed results I got for the F6F-5 are very close to numbers I have seen quoted for it carrying a drop tank and two 1000 lb bombs. Since the Corsair didn't 'officially' become equipped for bombs until the -1C/D models, I have no figures for a 'bombed up' Corsair until the we get to the -1C/D versions (and TBH, I haven't been looking).

Both models of the Hellcat and the later (-1A and later) Corsairs are recorded to have retained their drop tanks during combat on several occasions; their performance was sufficiently superior to the mid-war Japanese fighters that keeping the tanks was sometimes both possible and practical. I have to wonder if at least some of their numbers may be off because someone didn't notice the sets of numbers they were using included the belly tanks.

cheers

horseback

[JtD]

You'll need to engage low gear (2nd stage in game) in order to get any benefit from water injection. Both with and without water injection you're operating above full throttle altitude, where the benefit of water injection is nearly zero.

I would like to know what your "generally accepted" speed performance figures for the Wildcats are. I can tell you right now that they match or exceed the figures given in Americas 100000 as well as the figures quoted on ww2aircraftperformance.com.

F6F and F4U performance is modelled for clean aircraft.

[horseback]

Originally Posted by JtD

You'll need to engage low gear (2nd stage in game) in order to get any benefit from water injection. Both with and without water injection you're operating above full throttle altitude, where the benefit of water injection is nearly zero.

I would like to know what your "generally accepted" speed performance figures for the Wildcats are. I can tell you right now that they match or exceed the figures given in Americas 100000 as well as the figures quoted on ww2aircraftperformance.com.

F6F and F4U performance is modelled for clean aircraft.

The 'HUD' message telling you that water injection is engaged goes up even so. Who knew that the game would lie to me like that?

As mentioned in an earlier post, ww2aircraftperformance.com shows a test for the FM-2 with a level speed at 5000 ft of 312 mph true (502 kph); an F4F test for 4600 ft shows a true airspeed of 283 mph (455 kph).

Attached is a blowup of the chart from America's Hundred-Thousand for the Wildcats' various models' Speed and Climb performance, scanned from the book and then printed on graph paper in the forlorn hope that it would be made a bit clearer (Murphy made his usual appearance, alas). The FM-2's speed graph line is highlighted in pink, the F4F-4 is in blue and the F4F-3 is in green. As you can see, the FM-2's line at 5000 ft is clearly east of the 300 mph line, while the F4F-3/-4's lines are well to the west of it, around 285 mph.

I used the same references you claim you used.

cheers

horseback

[JtD]

The HUD tells you the water injection is active because it is. It works above full throttle altitude. It did in real life. There's just no increased boost any more, and therefore there's no meaningful extra power. As it is in real life.

In game, the F4F manage around 295 mph at 5000ft. So clearly, the Wildcats do not "fall well short of generally accepted performance figures". Two of them are clearly overmodelled, and one of them falls "somewhat" short of generally accepted performance figures, and that not even at all altitudes. Unfortunately though, at the important ones.

[Woke Up Dead]

Originally Posted by JtD

The HUD tells you the water injection is active because it is. It works above full throttle altitude. It did in real life. There's just no increased boost any more, and therefore there's no meaningful extra power. As it is in real life.

I think IL2 Compare helps you figure out at what altitude boost no longer makes a difference. There are two lines on each maximum speed graph: the speed at 100% throttle, and the speed at 110%/boost. In some planes, like the Hurricane and Spitfire, the two lines meet at 4-5000m.

[horseback]

Originally Posted by JtD

The HUD tells you the water injection is active because it is. It works above full throttle altitude. It did in real life. There's just no increased boost any more, and therefore there's no meaningful extra power. As it is in real life.

In game, the F4F manage around 295 mph at 5000ft. So clearly, the Wildcats do not "fall well short of generally accepted performance figures". Two of them are clearly overmodelled, and one of them falls "somewhat" short of generally accepted performance figures, and that not even at all altitudes. Unfortunately though, at the important ones.

I used the term 'well short of accepted figures' for the Navy fighters as a group, which was a bit sloppy of me. The Wildcats are, however, shockingly sssllllloooooowwww by any measure; over 10 seconds to gain a bit over 6 miles an hour can seem like hours after testing the Corsair at sea level. When you're struggling to maintain level flight by detecting whether the altimeter needle is moving (the variometer is at least a second behind the curve), the intervals take forever to go by, and when you finally reach the point where there just ain't no more, you glance at the speedbar and think "WTF?"

Even if they are about 20 kph faster than they should be, that impression is hard to shake.

In any case, the FM-2 is poorly represented, and if former pilots' direct testimony to me is to be believed, the tall-tail Wildcat could accelerate with the Zeros and Oscars they encountered in the Marianas and the Philippines (the old guys picked out all of the Japanese fighters from my then-extensive collection of 1/72nd scale models and named each one --and corrected some of the color choices I made). Even accounting for the usual hypercompetitive BS factor present any time Navy veterans of any age meet, that means that like its climb, the FM-2's acceleration should be pretty good as well, even if measured against beat-up, poorly maintained A6M5s of the later war period. My former landlord said (realizing for the first time that my wife was present) that the FM-2 was "a he-heck of a lot uh, peppier than the Dash Fours or even the Threes."

If it was anything like the one we have in Il-2 '46, there wouldn't have been three 70-something year old men in my living room that day in 1985.

cheers

horseback

[majorfailure]

Originally Posted by horseback

Notes on USN/USMC Fighters tested @ 5K ft.

1. The early Wildcats seem to compare with what I know of their performance, not spectacular but stable; however, the FM-2, which was 500 lbs lighter & somewhat aerodynamically cleaner than the F4F-4, as well as enjoying a 160 hp power advantage at altitudes up to nearly 20,000 ft, is portrayed in-game as even more sluggish than its predecessors. I was so surprised by this, I ended up re-running the FM-2 to ensure that I hadn't left the landing gear hanging down or something, but it was just as sluggish and 'meh' as the first time. Historically, this was simply not the case. The FM-2 was widely acknowledged as the 'wilder' Wildcat; being lighter, cleaner and more powerful at low and medium altitudes, it had superior climb and acceleration, and a somewhat better top speed at low and medium altitudes. It was a much better match for the Zero, even the later models. Someone's got some 'splaining to do.

Again: Just because an an engine model does more hp at some alt, it does not mean it does more hp at any alt. 5kft is near FTH of first stage of F4F -good alt for it. Try at 5km alt - FM-2 will be better than F4F.

Originally Posted by horseback

3. Both models of Hellcat continue to be a huge letdown. With or without water injection, it is portrayed as a slug, and much slower than the official numbers I have found. A standard F6F-3 should be capable of 290 kts/330 mph true airspeed, or about 530 kph at this altitude. If the Wonder Woman 'speedometer' is correct, that would mean an IAS of about 470/480 kph in-game. The best level TAS I got from the F6F-3 was just over 510 kph, and the best level TAS on the F6F-5 was around 515 kph, or about 460 kph indicated for both. Again, there was very little difference in acceleration between the two, in spite of the extra 200 hp or so that the water injection of the Dash 5 is supposed to have. Again, I re-ran the Dash 5 to make sure that I hadn't done something wrong. The main difference is in top speed, but from 270 to 380 IAS indicated, there is no difference.

cheers

horseback

At http://www.wwiiaircraftperformance.org/f6f/f6f.html I can find only 315mph at 5kft for an F6F-3 without water injection. Other tests are either with water injection, do not cover that alt or are not fully loaded fighters.

http://www.wwiiaircraftperformance.o...6f-3-02982.pdf
is interesting because it states that early F6Fs were problematic to rudder trim in a power climb.

[MaxGunz]

Water injection in game is with WEP?