P-47N‘s Flight Model is Crippled

[Irregular23]

The P-47N right now suffers from adverse stall roll, pulling just a little bit above the critical AoA and the entire plane immediately starts to roll like crazy, which is so extreme that no other prop plane’s stall roll could match. The stall characteristic is utterly different from the P-47D series. As you can see in the video:

It turns out that one important factor in the FM file related to the stall characteristic is mistyped. The factor ‘AfterCritMaxDistanceAngle’ is assigned to be only 3, which is 12.7 times lower than other P-47’s 38, which gives the plane extremely abrupt stall.
P-47N:

P-47D:

In case you don’t know how the value affect the plane’s stall characteristic, the value affects the process of the stall where the lift coefficient turns from linear to inverse parabolic. A small value will make the stall happens in a very small interval of AoA. Here’s a diagram comparing in MaxDistanceAngle =30(Blue) vs 38(Red) from the SAS forum of the IL-2 1946, as this value is inherited from the IL-2 1946 and I don’t have a developer’s tool to output the a polar for WarThunder.

Most prop planes in the game has the value > 30. Some plane gets very low value to simulate its poor stall characteristic, such as the Ki-44 got the value of 18 and it already made an abrupt stall. The P-47N’s AfterCritMaxDistanceAngle =3 basically render the plane useless, as it will experience the most abrupt stall in the entire game.

This is incorrect as the P-47N should have a similar stall characteristic just like previous P-47D series, as it was stated in the report FLIGHT TESTS OF THE P-47N AIRPLANE AAF NO. 44-88406:

Which is very gentle and with little tendency to drop left, so it couldn’t be strong rolling moment as showing in WarThunder:
P-47 stalling

So yes, the stall characteristic of the P-47N should be fixed, the Typo in the FM file should be corrected from 3 to about 30-38 in sure the plane functions like normal.

Another bug is that despite having a slotted flaps with over 50% of the span, the P-47N with full flaps only gets a maximum lift coefficient of 1.65, which only gained 0.1 from no flap position, which is utterly wrong considering the P-47D has the CLmax of 1.85 with full flaps with a gain of 0.4 from deploying the flap, so that’s another bug to be fixed.

Of course, the minimum fuel load of 50min, is a long mistake that should be discussed. The P-47N manual listed its normal gross weight of 13,854lbs, which is similar to that of P-47D:

The SAC file gives the designed weight 13,823lbs. The main and aux tank capacity of the P-47N is unchanged 370 gal, same to the P-47D. The wing tanks are optional and can be flew in empty, as we see in cases of J2M and F4U, both types of aircraft have wing tanks for extended mission, but not often used, and that portion shouldn’t be counted in calculating the minimum fuel load.

P-47N to be fixed:

1. Stall characteristic
2. Flap lift polar
3. Minimum fuel load.

Hope it can be a useful thread to discuss the FM problem of the game.

[RunaDacino]

Can you please make an official bug report? The reason i ask you to do so as you have the files and documents to upload already. I’ll link it in the sim LFG discord and subreddit for better visibility if you aren’t present there.

[Irregular23]

I tried to make some official bug issue, previously the F4U FM problem and the incendiary round, but get no response. I thought if hopefully a moderator saw the thread and then make the issue there might be more chance to get a reply.

[Irregular23]

I’ve created the issue: P-47N stall characteristic and flap lift are bugged // Gaijin.net // Issues

There’s also a one related to the F4U: F4U-1/4 series incorrect elevator deflection angle // Gaijin.net // Issues

[RunaDacino]

I’m passing it along. after that, we can only hope.

edit: Posted to sub and discord!

[kizvy]

looks fixed, nice

[Alpharius11348]

if anything the p47N should have slightly better stall characteristics than the p47d

[Alpharius11348]

I like how vague the response is, sometime from now until the game is abandoned there will be an update that fixes this

[Irregular23]

The issue was said to be fixed… But after some flight tests I found the stall seems to be even worse… The plane will not only sudden roll but also get into a flat spin. I don’t know if gaijin really fixed the problem

[PercussionCap]

@Irregular23

The wing tanks are optional and can be flew in empty, as we see in cases of J2M and F4U, both types of aircraft have wing tanks for extended mission, but not often used, and that portion shouldn’t be counted in calculating the minimum fuel load.

AFAIK they won’t accept this, it is similar to the weight increase of N1K2-J a while back. One of the internal fuel tanks was only filled in the “overload” condition, but it was counted anyway.

J2M’s wing tanks should still have a little fuel in them in-game.

[RunaDacino]

Did some light testing of my F4U-4 post-update:

I can now pull up to 16.9 degrees AoA before I stall out. 17 degrees causes one wing to drop violently (depending on rudder and torque).

At 16.9 degrees AoA we’re at 93% of critical AoA.

This is without maximum stick deflection. With maximum stick deflection & no rudder compensation on a left-hand turn (full yank: 18 deg aoa)

Result: at full yank without rudder in a left hand turn she immediately spins out pretty violently while WEPing.

This is a super rough test, but it looks like we got full elevator deflection opened up with full-real controls!

[Irregular23]

Already had some fun on the F4U-1D :>
With flap extended and more AoA available, the Corsair is much more manoeuvrable than before.

[RunaDacino]

Weirdly, it seems fuel has a MASSIVE impact on stall characteristics.

Compare F4U-4B at min fuel vs 30 minutes.

At min fuel she stalls super gently. Wing drops, but if I take hand off controls she settles down.

(seems true for f4u-4 as well.)

20 min still seems to induce violent spins for f4u-4. 4B has gentle stall at 20 mins.

F4U-4 seems to be gentle on stalls around… 18 minutes. 19+ you risk violent spins, 18 and under it seems to be self-righting once you stop inputting elevator.

[Irregular23]

I haven’t try F4U-4 in depth. But I felt that F4U-4 is more easy to control than -1 near the stall, with combat flap extended, the -4 could pull full stick without stall.

The -1 will stall with combat flaps down, and it has poorer longitudinal stability such that the AoA periodic swing around 13-14 deg, in the cyclic period about 1 sec, and that the right wing will drop every 1 sec if you pull right at the critical point with flaps extended. A bit annoying during the dogfight, also the F4U-1’s flap lift coefficient is lacking compared with the -4 series.( CLmax 1.9 vs 2.1)

[RunaDacino]

Any experience testing with 47s? I haven’t really flown them to be able to compare since it’s more subjective feeling than “check max AoA on F4U-4 and compare versus your report.”

[Irregular23]

I made a brief flight handling test on the P-47N and it seems to be great at stall. No more sudden thrown into flap spins.

[dannaryan-psn]

It’s only a good thing if aircraft get full elevator usage now. I hope they’ve also fixed the P-40 as that FM was atrociously bad, the thing couldn’t even stall it’d just lazily roll over.

If the Corsair stalls the way it should now it’s a very very good thing. Before the Corsair had one of the most overly forgiving flight models in the game.

If aircraft stall properly now then well done Gaijin!

[Irregular23]

I would say even though the Corsair gets full elevator deflection and now is able to perform accelerated stall. Its stall characteristic is still inaccurate. Though enough to reflect some accuracy.

Currently the Corsair had around 17-18 deg critical AoA in clean condition, and it tends to roll right when stall in power-on condition. The stall is also quite gentle. IRL the Corsair has <=16 deg critical AoA in clean and performs a strong leftward torque roll when stall, especially in power-on landing configuration. Which was notorious and crippled its suitability as a carrier-based fighter.

[dannaryan-psn]

I tested the Corsair last night and it’s still far too forgiving and almost needs to be made to stall. The Corsairs were fitted with stall strips to the wings to give the aircraft a more predictable stall in carrier landings however this did not help the Corsair with accelerated stalls, the Corsair was always known as a prickly aircraft to fly.

That massive prop and engine was known for creating a LOT of torque. In game it’s still on rails, the aircraft in SB is still massively overperforming.

I’ve noticed other flight models feel different too, the C.200 feels a ton more agile to me which is great but it’s still prickly to fly on the limit. Stall behaviour is still odd though, you can get it to drop a wing but at times it auto-recovers… still better than not stalling at all though.

[RunaDacino]

What fuel levels were you working with? At least for the F4U-4 fuel makes an incredible difference for how vulnerable it is to accelerated stalls (under ~19 mins it’s very gentle. At 30 it feels it can enter a violent one but there’s a second or two of buffeting before you drop rather than the immediate response you get in 109Gs or Fw190s.)