[NO BUG] low speed speed/pitch stability

[bbrz]

Noticed that if you have the Yak-52 trimmed for a glide at 160km/h with full flaps and gear down at idle and you apply one click of nose up trim, that the nose starts to rise...which is expected.

But this trend never stops. The slower you get, the faster the nose starts to come up, and without any pitch input the Yak increases the pitch attitude well into the stall warning AoA.

Is the real Yak that unstable?

This pronounced pitch up occurs during the flare as well. Once you get below approx 130-120km/h, the nose starts to rise on its own.

[NineLine]

This concern was raised during testing as well, but its more a matter of our controls, and the fact that the real forces in the real aircraft would be felt through the stick more, and you would counter as they happen. Its possible that this could be better shown with a force feedback stick, but for most of us, you just need to apply pressure to counteract the pitch.

[bbrz]

Thanx for the info that this effect has been discussed :)

I was just wondering because this pitch up effect can usually only be observed in planes with highly swept wings.

[AcroGimp]

My Yak lacks enough nose up trim authority to duplicate this behavior but from a pure aerodynamics/physics point of view it should continue to slowly pull up until reaching either the trim neutral speed for that trim setting or critical angle of attack at which point it would mush or actually stall/break.

 

'Gimp (DISCO vVMA-212)

[bbrz]

Thanx :)

I was a bit surprised that a single trim click causes the AoA to increase by 12° and a speed drop by 70km/h.

Edited August 3, 2018 by bbrz

[MonnieRock]

My Yak lacks enough nose up trim authority to duplicate this behavior but from a pure aerodynamics/physics point of view it should continue to slowly pull up until reaching either the trim neutral speed for that trim setting or critical angle of attack at which point it would mush or actually stall/break.

 

'Gimp (DISCO vVMA-212)

 

Thank you.

 

Nice to hear input / impressions from people who actually own one of these aircraft. :thumbup:

 

 

Happy Simming,

Monnie

[Robert31178]

I'm a noob on this stuff, but isn't the described behavior in the first post akin to entering a deep or accelerated stall?

[Justin Case]

I'm a noob on this stuff, but isn't the described behavior in the first post akin to entering a deep or accelerated stall?

 

A deep stall is often caused by shifting of centre of lift or pitch controlling surfaces being shadowed aerodynamically when increasing angle of attack. I believe the term “deep” stems from the severity and often unsolvable nature of a deep stall.

 

An accelerated stall is just reaching critical AOA through pitch input at speeds higher than that for a 1G stall.

 

I might be oversimplifying this but it’s been a while since I’ve opened that book.

[Robert31178]

ah, ok thanks!