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Bloodsplatter

Trim issues with P-39

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Is anyone else having having problems trimming out the pitch on the P-39. Full nose down trim doesn't do much and I find myself flying around with the stick well forwards fighting the force feedback. This makes aiming, especially when rolling out of a turn, difficult. I found a post from EAF19_ Marsh stating he was having similar issues but everyone else seems to be fine.

 

 

 

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I'm having the same issue.  With full nose down trim, keeping her steady while making a strafing run is quite the challenge considering the nose wants to pop up like a surfacing porpoise.  Just have to keep working at it I guess.

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The instantaneous agility had to come from somewhere. We could ask for the fly-by-wire mod, perhaps? ;)

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P-39 manual does state it has a severe pitch up tendency while diving. So I guess that's what devs went for.

 

It does not say at what speed this gets "severe", so manual leaves some room for interpretation. The tendency is however mentioned in the context of diving 'good to knows' and max dive speed.

 

 

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Ehret... trimming has nothing to do with instantaneous agility. You may never be able to fly a highly unstable aircraft 'hands free' but you can still trim it out to neutralise control forces. It's piloting 101.

 

a_radek...  Actually, the manual states, "It is necessary to trim nose heavy when diving this airplane, otherwise the airplane will make a severe pull-out as speed is attained". This implies the aircraft CAN be trimmed nose heavy. In the game at the present, it is impossible to trim nose heavy in level flight, let alone in a dive. You can't even trim it neutral, the planes always  tail heavy no matter how you adjust the trim. THIS IS the problem. 

 

Bloodsplatter

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Thanks Bloodsplatter - not just me, then!

 

TBH the 190 also seems to have a similar negative trim issue whereby the indicator stops about half-way to full fwd and you need some stick input as speed builds. In the P-39 I find this exacerbated by the nose-up kick triggered (pun!) by firing the guns. Am really enjoying the P-39 and everything else in 3.01 but this was puzzling me somewhat.

 

Thinking about it, I wonder if this is a consequence of the short distance between the CoG and the elevator, whereby the FM trim has difficulty generating sufficient force. I would be very surprised if a real P-39 could not be trimmed nose-heavy with full [nose] ammunition and low fuel.

Edited by EAF19_Marsh

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1 hour ago, Bloodsplatter said:

Ehret... trimming has nothing to do with instantaneous agility. You may never be able to fly a highly unstable aircraft 'hands free' but you can still trim it out to neutralise control forces. It's piloting 101.

 

The other definition of trimming states that when no control inputs are given, the airplane maintains speed and altitude. If you can not do this "hands free" the airplane is not/can not be fully trimmed, normally. This is a common trait of agile frames and the fighter may be deliberately designed that way.

 

In the case of some planes, like the 109, the the trim setting does affect turning ability, actually.

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Odd.  Far from being 'impossible',   I can certainly trim it to descend at full cruise speed though I admit it does need a lot of trim for level flight.   I will have to see just how much nose down it will achieve.

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The fuel load should not affect the GC, as fuel-tanks are in wings.

 

Maybe some effects (drag or lift?) in the nose, which is positioned unusually far from the GC, have enough leverage to pitch the aircraft?

Edited by Ehret

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Quote

Maybe some effects (drag or lift?) in the nose, which is positioned unusually far from the GC, have enough leverage to pitch the aircraft?

 

I think it is the opposite, the closeness of the tail reducing the force available. I suspect that may also be part of the difficulty in spin recovery.

 

It can be trimmed for cruise, but above 300 kph I find I need to hold the nose down.

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@Ehret         I think we have our wires crossed here. I completely agree that the P-39 couldn't be trimmed to fly hands free but it could still be trimmed out so that only slight (but constant) minor corrections are need to hold a speed and height. We can't do this in BOK. Watch THIS 1943 training video made by the USAAF to train it's P39 Pilots. It repeatedly talks about trimming out the aircraft before starting manoeuvres.  In particular, at 18:25, when talking about loops it says to trim the aircraft out for a cruise as the loop contains both high and low speed elements and trimming for a cruise is the best compromise. Cheers :)

 

@56RAF_Roblex          That's very interesting. I'm using directional arrows to control my trim and at nominal power, 100% nose down trim still results in the aircraft being very tail heavy.  I wonder what the difference between your system and mine is....

 

----------------------------------------------------------------------------------------------------------------------------------------------------------

 

Ok, I think I've found the problem, on my pc at least. Pitch trim on the P39 isn't working at all.

 

I discovered it I got the P39 to 120mph (Water 60%, Oil 40%, Mixture 75%, Pitch 75%, Throttle 45%), the P39 would hold height, speed, and fly hands free. Its the textbook example of a properly trimmed aircraft. I then adjusted the pitch trim from 100% to -100% and NOTHING happened. It just stays exactly where it was, cruising straight and level at 120mph.

 

Anybody know how to fault this with the developers?

Edited by Bloodsplatter
two posts merged together
  • Upvote 1

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Is this only an issue for people using force feedback? I've not noticed any problems with trimming the P-39 so far.

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@AndyJWest       Yep, you're 100% right. If I turn off force feedback, I can trim the P39 without a problem. Turn on force feedback and I have nothing.... 

 

Thanks

 

Bloodsplatter

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Only problem I have with it is when i snap roll it to the left by kicking in left rudder and rolling it quickly and stopping it quickly the rudder stays stuck in left of slip indicator (ball).  i have to use rudder trim to get it back to center, I have found this bug with a couple of planes now... A-20 does it when i kick in hard left rudder..

 

anxiously awaiting the first hotfix..................  ;)

 

 

Cheers

 

Hoss

Edited by 19//Hoss

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Glad someone made that thread yet : Yes I was experiencing the same weird thing : simple, I was systematically trimming to -100% thinking it could help, guessing that was weird but we talk about a particular plane with CG quite "on the tail". I now understand why it was so difficult to me to take her off as soon as front wheel leave the ground because she was soooo nose up suddenly...

 

But you're right, @Bloodsplatter : It's just bug, related to FFB. Oddly we FFB users don't have any efficiency from the pitch trim even if we can actually see the command move on the plane's aileron. Then if you try unticking the FFB, well... It's another story ! :rolleyes:

 

I think we should report this to the devs quite fast, maybe we could provide some clear evidences (but I guess devs do have an FFB (good'ole MS FFB2) and can verify this easily by themselves.

Edited by Solmyr

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MSFFB2 user here, I've noticed this as well. Flying with -80% pitch trim down at all times and still porpoising quite a lot, makes it hard to aim especially at ground targets. 

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MSFFB2 and G940 users, we have bug reports on the following threads:

 

 

 

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@Bloodsplatter

 

this is is fixed for me now. I can trim the pitch for level flight and my FFB stick adjusts its “center” position accordingly. 

 

I can finally enjoy the P-39. 

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51 minutes ago, variable said:

@Bloodsplatter

 

this is is fixed for me now. I can trim the pitch for level flight and my FFB stick adjusts its “center” position accordingly. 

 

I can finally enjoy the P-39. 

 

what made this to be fixed for you?

 

we were discussing this odd behaviour yesterday night with my squad, and a mate raised the fact that it was linked to FFB.

 

we were all flying P-40 in which we observed the same behaviour, but I have to test the Cobra tonight to see if it's fixed for me aswel... anyway, I'll have a look at the bug report

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@Bloodsplatter

 

On 3/26/2019 at 7:50 AM, OBT-Psycho said:

 

what made this to be fixed for you?

 

we were discussing this odd behaviour yesterday night with my squad, and a mate raised the fact that it was linked to FFB.

 

we were all flying P-40 in which we observed the same behaviour, but I have to test the Cobra tonight to see if it's fixed for me aswel... anyway, I'll have a look at the bug report

 

No idea.  I just tried flying the P-39 for the first time in months (avoiding it because of the FFB pitch trim issue) and it was working great.  I haven't hopped in a P-40 in forever so I'll have to give that a go.

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Posted (edited)

No change for me. Still unflyable. I recall (imperfectly--I'm old) a discussion in which it was argued that skewing stick range when trimming is realistic, so no curve-centering as with Ride of Flight. I'll buy that, but why not make a centering for FFB only--that is, re-center FFB while retaining range skewing?

 

To provide some context for those not having FFB sticks: in my case, at cruise with -100 trim, the stick is about 1 inch from the forward limit, the a/c is still climbing, and there's still a noticeable rearward FFB fighting me.

Edited by buster_dee

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