The A2A Simulations Community

Been flying the Tomahawk IIb for about 20 hours, and am curious about the design for the tail. I've noticed that in a turn, it's almost coordinated all the way until into a steep bank, when opposite rudder is needed to keep the ball centered. I've also noticed that as the aircraft slows down the elevators have a tendence to "fall out," allowing the nose to rise and the aircraft to stall.
Is this the way the real P-40 behaves or do I need to mess with controller and config files?

The reason for the question is that all the aircraft I've ever flown, sim and IRL, as you slow, the nose drops and the aircraft stabilizes while descending and maintaining the original airspeed (more or less). Speed reduction is brought about by trimming the nose up. If I'm not "all over" the P-40, I'm "all over" the landscape.

I can think of several ways to modify the configs to change this, but I'm pretty sure (from several A2A aircraft) that the modelling is correct, which leaves me with two possiblities - I need to change some settings on the Saitek controllers or everything is correct and I need to get serious about learning this aircraft.

Dave

No, don't change anything! Its built for maneuverability, so I think you have a pretty small static margin. That Fuselage fuel tank really makes a difference, so try using up some fuel from it and getting your CG farther forward, and you will find your long. stability improves very noticeably.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

And....ignore the ball!!! In FSX it is a POS.

Fly the horizon, not the ball, or you will never get a coordinated turn.

I'm not sure what you mean by the elevators "falling out". It looks like you mean becoming more effective..but this doesn't track? This is the only way that the nose would "rise" in the turn, as the in this situation you are trading some of the wing's vertical lift vector for turning vector. This is why elevator is needed, to replace that "loss" (not actally loss but reassignment....) of lift.


The P-40 has a large side profile and at high bank angles that slab can act as a lifting surface in some circumstances, meaning that the nose may climb even without as much elevator as you would expect.

Darryl

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I think what he means is that in LEVEL FLIGHT the aircraft behaves a bit unusual: If you raise power, it will pitch down and loose height, if you reduce power, it will at first raise the nose and climb, until it is slow enough to sink... I also found it a bit strange at first, but it is most noticable with empty fuselage tank and full reserve (foward CG).

Can someone of the more experienced RL pilots comment on this? I am curious if there is an explanation what leads to this behaviour.

BR,
E.

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Killratio is a real pilot

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Ron
B-17 AIRFRAME 710 HRS PLUS AND CLIMBING




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That's kind of an understatement...

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Lukas

No intentions to step on Darryls toes, but perhaps someone with warbird-experience can tell first-hand.

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I have same experience with A2A P-40: if the speed drops, the nose rises. If the speed rises, the nose drops. This means, that it's absolutely impossible to trim to fly level: either you set the nose too high, the nose rises more, speed drops, nose rises more, speed drops, stall, spin... or you set nose too low and speed increases, nose drops, speed increases, nose drops, dive and rip off your wings. No matter what amount of throttle and what amount of trim, no combination can keep the plane level even just for 30 seconds to read the map for example.

But I think this tendency is exactly the opposite to what you said: it's when fuselage tank is full, when it tends to behave this way. Which is why I use that tank first (leaving around 5-10 gallons in it because the plane should be landed with fuselage tank selected, IIRC, thus shouldn't be completely drained). With fuselage tank full, the plane is outright awful to keep stable in any speed, power setting, climb, level or descent. With CoG at rear, it's understandable that the nose will be higher for fixed speed and elevator trim. It's just this odd way to inverse speed to trim requirement baffles me. I thought that even with rear CoG, it would merely have a more nose-up attitude but the nose would still drop when approaching stall, instead of the otherwise.

Then again, I'm not saying it's impossible to have this sort of behaviour. I think there has been some planes that actually did perform that way, like Wright Flyer for example: if you approached a stall, the main wings stalled first, and with it's elevator being positioned in front of main wings, the nose pitched up violently slowing it down further, and the aircraft became almost instantly unrecoverable due to the "nose pitch up near stall" tendency. Luckily these Wright Flyers didn't fly very high so they were able to walk away from the wrecks they all too often found themselves in.

EDIT: fixed nosedown to nose-up. Obvious mistake from the context but I fixed it anyway.
EDIT: "trim", not "trip"

I think the question y'all are getting at is whether a full fuselage tank would actually push the CG aft of the CL in the real thing. (although none of you have yet used the word Negative Stability to describe what you are seeing ) If you are using the fuel tanks like you're suppossed to, I think you will all be okay.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

I call it "unstable equilibrium state" rather rather than "negatively stable". But I'm more a physics nerd than aviation so I don't know all the aviation lingo.



It is "okay" as in "it's flyable" (it just cannot be trimmed to a stable flight but requires constant stick input, and is thus pain-in-the-ass).

I never leave the reserve tank empty while fuselage tank full (which would result in worst case scenario for CoG). Even filling every tank full pushes CoG so much back that it causes this negative stability on pitch axis. But it does correct itself during your flight if you keep draining the fuselage tank. Half an hour of flying and it starts to behave quite nicely. It's quite obvious why it's recommended to drain that tank first. Taking off and climbing through a thunder storm is challenging though, if you don't drain the fuselage tank prior to starting it up: a sudden gust of wind can twist and turn the plane around quite a bit and that negative stability is just the last thing you want in that situation.

Then again: it's not quite clever to take a warbird (any warbird) to a flight during a hurricane (or even the stock "major thunderstorm" preset).

I want to thank you all for the clear and cogent responses. I had looked at the config for fuel tank locations, but it never occurred to me the significance of the fuselage fuel tank cg.
I've tried a number of aerobatics and found the rudder authority to be just fine - and I've since been unable to duplicate my original turn coordination problem.
Since adjusting the fuel level in flight is so easy with this critter, I'm going to mess with finding a configuration that will allow stable altitude trimming.

Way too much fun. Thanks all.
Dave