limit of trim = limit of travel?

wrote:
On May 8, 6:22 am, nospam wrote:

For those who were wondering about tab effect, or indeed elevator effect
on total tail lift the following may help;
Each item can be considered separately.
There will be a basic tail camber lift component which in many cases is
zero.
Then find the tailplane AOA and from the lift curve slope find tail Cl -
put that into the normal lift equation.
At that particular tailplane AOA, select the elevator AOA and again find
the Cl from the lift curve.
Then do the same for the tab.
Add the 3 solutions to get total tail lift.
Do this for the complete range of angle of attack for each component and
you will know the total range (and direction) of tail lift.
Cheers

Sorry, but each item can't be considered separately, any more
than an aileron can be designed or its effect determined without the
wing ahead of it. Removing the elevator from the stab, physically,
would make the stab almost useless, especially if it has an airfoil
shape and/or has aerodynamic balance. Working out numbers for an
elevator without considering the stab's effect on the camber and AOA
for the whole assembly is also useless. The air doesn't decide what
bits it will react to or ignore; it only sees an airfoil of some sort,
having at any given instant a particular camber and AOA, and the tab
is part of that assembly, whether deflected or not. The tab doesn't
contribute much, if any, to tail downforce, but does affect elevator
float position, and that elevator position sure does affect downforce.
Airplanes are not the sum of their parts. I wish it was that
simple.

Dan

Geeez I hadn't realized how thick you guys are.
Of course the tail, elevator and tab are taken into account - AOA tail
is wing AOA plus downwash, elevator AOA is wing AOA plus tail downwash
plus elevator angle, tab AOA is wing AOA plus wing downwash plus
tailplane wash plus elevator wash (at a particular elevator angle).
Your comments on elevator float position are irrelevant when one decides
to do calculations at a particular elevator angle. Float position is
nice to know for stick free stability measurements, but both the pilot
and the engineer can set the elevator angle at any they wish
irrespective of float.
If you really believe that aircraft are not the sum of the parts I would
suggest that any study of serious aerodynamic theory is probably beyond you.

References:
Duncan W. J. Control and Stability of Aircraft
Babister A. W. Aircraft Stability and Control
Perkins and Hage Airplane Performance Stability and Control

Get these out of your library you might actually learn something!
and
Course Notes Empire Test Pilot School.

The top 3 are widely used texts for aeronautical engineering degree courses.
I know I wrote I would not be back and I now realize that this group is
not one where serious informed discussion can be had.
I really won't be back.