Stability at High Altitude

[FOOTE]

Hi guys,

Currently studying up for ATPL aerodynamics and systems and have come across something that I haven't seen before with regards to stability (directional stability to be more specific). I have the AFT notes and whilst I am not questioning them I was hoping someone could explain to me why directional stability is affected by flying at high altitude and also why lateral stability is unaffected by high alt's?

Cheers,

Matt

[Draggertail]

Google is your friend. Try this one.


The Effect of High Altitude and Center of Gravity
on The Handling Characteristics of Swept-wing Commercial Airplanes


High-Altitude Handling (http://www.boeing.com/commercial/aeromagazine/aero_02/textonly/fo01txt.html)


Cheers

[FOOTE]

Thanks, it all makes sense now. Not sure why I didn't think of using google.

Cheers

[Oracle1]

Glad you brought that up, wouldn't have even known about the topic. Google cant help if you don't know what you are looking for. Read the results with interest.

[FOOTE]

Glad I wasn't the only one. If anyone has recently sat the CASA AASA exam would you mind letting me know what sort of questions you got asked? And how they compared with the material you studied with?

Cheers

[Greedy]

Foote,
The mention of both directional stability and lateral stability with altitude leads me to suspect that the area of knowledge being examined is Dutch Roll. The interplay of the two modes determines the dutch roll characteristics of the aeroplane and is altitude dependant. Again google is your friend. The previous poster pointed to a googled article concerning longitudinal stability but your original post leads me to think dutch roll is more relevant.
The prune flight test forum includes engineers and others who may be able to better clarify any questions you have.
Good luck
Greedy

[FOOTE]

Hi Greedy,

You are bang on, it was concerning dutch roll. Thanks for the tips.

Matt