Saturday, May 14, 2011

Bouncy Landings - Yes, it's an angle of attack problem!

I hope I am not sounding like a preacher with my angle of attack posts ...

I assembled this quick video after some really bouncy landings I performed in IL-2 1946.



Cheers,

9 comments:

Jomni said...

That's why I hate tail draggers. :)

Anonymous said...

Nah, you bounced because you tried to force it down before it was ready to land - the nose pointed down to lose the excess height.

You were still at approach speed, and didn't flare - levelling the flight path with the wheels about 6" above the ground. The aircraft is then held off the ground until it settles in the ground attitude the last bit.

Quite probably you are rounding out too high as well, with a progressive pull, the flare should end with the aircraft parallel to the ground but only 6" to 1' above the ground - a common error is to be 'ready' to land while still 6' to 20' above the ground, or even higher.

Try flying a slower, flatter aproach, but carrying a bit more power until over the threshold, if engine failure is no risk, or finding your engine-off (or idle) glide approach that gives you a 'dead' airframe within about 5 seconds of flaring. Endless 'floating' is a symptom of too much energy, either too high, or too fast.

JC said...
This comment has been removed by the author.
JC said...

Hi Jomni,

Me too!

Anonymous,

Almost all you wrote doesn't add to the point to the video (why the aircraft bounced, from the lift point of view).

Cheers,

Javier said...

-Posiblemente el efecto tierra sea el causante, pero no creo que en IL-2 este modelado, me sumo a lo que dijo Anonymous es un tema de falta de quiebre de planeo y dejar que el avion se siente solo, si uno hace una transicion progresiva es capaz de lograr una "sentada" sin rebote.

-Saludos, escribi en español porque entiendo que Ud. vivio en Argentina, buen fernet.

-Javier B.

JC said...

Hola Javier,

Gracias por tu respuesta. Entiendo lo que me dicen vos y anonymous. Estoy de acuerdo en que practicamente empuje la aeronave hacia la pista. Pero insisto que el golpe levanta la nariz aumentando el angulo de ataque y consecuentemente incrementando el "lift".

No me trates de Ud. que no soy tan viejo. Reconozco que siendo de Cordoba tengo mas de un fernet en mi legajo. :)

Un abrazo,

JC

Anonymous said...

But it isn't just about AOA - the angle of repose is higher than the normal landing attitude (if only by a little - bad practice to land on the tail-wheel, three point is the steepest usable incidence).

What makes a bounce is that this AOA is only suitable for a certain energy level (or below), and excessive speed, plus in the first landing dumping the excess height are what allows any form of bounce at all.

(A football dropped from 6 feet might bounce up 4-5 feet - but once placed carefully onto the ground won't bounce as it has no energy to convert back into height).

Javier said...

-Fernet Branca con coca uhh muy bueno.

-Estaba pensando el tema y puede ser "porpoising", un par de paginas pueden explicarlo mejor que yo, pero he visto varios accidentes por aquel motivo.

-I was thinking about the subtjet, maybe is a porpoising is kinda difficult to me explain it but i saw several accidents as a result of the porpoising, only the pilots pride was harmed.

http://www.pilotoutlook.com/airplane_flying/porpoising

http://www.aerospaceweb.org/question/dynamics/q0233b.shtml

JC said...

Hi,
Thanks for your comments.
I read you guys and get this feeling that we are talking about the same thing ... just with different words.
:)
Cheers,