P38 stall phenomenon

[354thFG_Panda_]

I've been playing around with the P38 for a fair bit and I manage to get into this situation where it will stall but just kind of falls very flat...

Could anyone from the Dev team or someone knowledgeable explain the phenomenon?

 

Few things to note:

- This is easily fixed by nosing down. I still have elevator response to push down and to keep it in this position.

- Ailerons are still working at these angles and speed.

- Engines on providing propwash but is it too much way past stall and even at this angle of attack??

 

 

 

[Cpt_Siddy]

You have enough prop wash to maintain control of the attitude and not enough lift to provide level flight.

You have turned the plane in to giant vortex generator that is sapping all the energy your engines generate and you found a stable way to do it all the way to the deck. 

 

I guess it is possible to do with single prop plane, but usually it will spin out of control because of torque and uneven prop wash coupled with reduced control authority. The twin engine configuration lends more stability and this is the result. While this phenomena looks funky, i dont see why it is wrong.  

[6./ZG26_Klaus_Mann]

It's called "Sackflug" in german and some Planes to it better than others. It depends on CoG, Fuel Load, Aileron and Wing Design and the Magic of Twin Engines.

Even at that Angle you still have energetic Airflow over the Wing Sections behind the Props and some Effect in the Elevators.

The Bf110 does this as well.

[SYN_Mugue]

Just like Air France...

[354thFG_Panda_]

Thank you for explanation

[Bremspropeller]

21 hours ago, 6./ZG26_Klaus_Mann said:

It's called "Sackflug" in german and some Planes to it better than others. It depends on CoG, Fuel Load, Aileron and Wing Design and the Magic of Twin Engines.

Even at that Angle you still have energetic Airflow over the Wing Sections behind the Props and some Effect in the Elevators.

The Bf110 does this as well.

 

It's called "falling leaf" en anglais.

 

The only thing surprising me here is the in-game P-38 having enough elevator authority to pull it off. The deployed dive-brakes are a giveaway, though.

It's usually what limits me in this aircraft. Not sure if it has been fixed or not, but the airplane will run out of elevator and trim on final-approach, which is...unrealistic.

 

[gimpy117]

15 hours ago, Bremspropeller said:

The only thing surprising me here is the in-game P-38 having enough elevator authority to pull it off.

I think it's been established that low speed elevator authority can be suspect in this game. just wasn't expecting the P-38 either. 

[Cpt_Siddy]

14 hours ago, gimpy117 said:

I think it's been established that low speed elevator authority can be suspect in this game. just wasn't expecting the P-38 either. 

 

Actually i think P-38 will have rather good elevator authority IRL at low speeds, as it don't have so much of the backwash eaten by fat fuselage skin boundary layer losses and have a nice blast of air right at the center part of the tail producing nice balanced, turbulence free, moment arm.

 

Where there is huge turbulence losses is the both sides of outer wing. Making me wonder if any actual aileron reversal could occur due to change of area of the wing into incoming air stream. Considering that incoming air under the wing now is the dominating force on that part of the wing. 

Edited August 30, 2021 by Cpt_Siddy

[Guest deleted@258843]

Aileron effectiveness as seen in the video in this situation seems suspect to me.

 

They're outboard from the prop wash, and the wing is flying well beyond its critical angle (certainly beyond any angle where aileron effectiveness could be explained by wingtip washout).

 

Given that, downward aileron that would normally lift a wing should only cause it to stall even more and create additional drag in this scenario -- so instead of the wing happily responding and helping to maintain lateral stability in response to aileron input as it seems to be doing in the video, the wing should drop and be pulled backward. Roll control would be reversed, and the aircraft would be unstable laterally (and directionally if pilot is not quick to respond with rudder).

 

It's one thing to dance on the pedals to be holding up the wings in this situation, but that's clearly not what's happening in the recording. 

 

For what it's worth, this is also not a "deep stall" -- and shouldn't simply be dismissed as such -- as airflow over the horizontal stab has not been blocked and OP mentioned there is still plenty of pitch authority available. Yes, deep stalls are real, but that doesn't explain the behavior in the video.

 

The problem is the lateral stability in this scenario (the retention of roll damping) and ailerons still being an effective means of control.

 

 

Edited August 30, 2021 by Kablamoman