elevator /pitch control

On 4 Nov 2003 16:49:14 GMT, (John Firth)
wrote:

Here is a reason for buying a ship with aerodynamic trim, not just
a spring on the stick.

This is the cause why an elevator trim tab is required according to
JAR 23, by the way - it's a safe backup control.

Bye
Andreas

Andreas Maurer wrote:

On 4 Nov 2003 16:49:14 GMT, (John Firth)
wrote:

Here is a reason for buying a ship with aerodynamic trim, not just
a spring on the stick.

This is the cause why an elevator trim tab is required according to
JAR 23, by the way - it's a safe backup control.


But aerodynamic trim is bad in term of aerodynamic efficiency, I think
this is the reason why all modern gliders have a spring trim. Should we
always degrade the performance for a case taht should never happen. An
exeception to this bad efficiency is the system I have seen on Robin airplanes,
i.e. a balanced all moving elevator (hinge at neutral point) with a servo (anti)tab
adjusted by the trim. The drawback of this system is that the force needed
to move the elevator from the trimmed position becomes huge when speed increases.