Tony, great explanation!

To add a little to this fun little conversation, what strikes me is
what it reveals about the result of someone teaching himself to "fly"
via a PC "simulation". I work in the aviation simulation industry, and
MSFS could conceivably be describes as a "training device", OK for
procedures and avionics training, but not for primary flight training.
As a result of his self training, MXS has been completely misled by the
way his "game" flies, and is drawing some wrong (if somewhat
interesting) conclusions!

The whole concept of the trim limiting the control authority is a
classic example of this. In a real aircraft, as previously stated, the
trim is used to relieve control pressures. It does not limit control
authority (except for the very limited effect of a trim tab fully
deflected, which is allowed for in the design of the control surface),
since the control authority is required to be sufficient to cope with
any conceivable need. I think the worse case is usually full gross (or
max landing) weight landing at full forward CG - that will drive the
size and power of the elevator. Any bigger, and pitch becomes too
sensitive at higher speed and adds useless drag.

Also, MXS does not seem to appreciate that the control position (of the
elevator) is a function of the speed (or AOA) of the aircraft, not the
trim position. I can slow down and crank in full nose down trim and
fly just fine with the stick almost fully aft - and get a good workout
in the process! And as the pilot, I know I'm slow since the stick will
be in my lap. As I then crank the trim in, the control surface will
not change position (especially on aircraft with no trim tabs), but the
stick forces will go away (without the stick moving). But I will not
add or remove any control authority - the stick is still way aft! As
a pilot, you are taught this from the beginning - the relationship
between stick position, speed, angle of attack, CG, etc. Their
interrelation is what makes flying so interesting - and where low level
PC "simulations" fail the most.

Oh, by the way, many aircraft do not have any trim tabs at all - most
gliders use springs in the control circuit, J-3 Cubs move the
horizontal stabilizer, the F-4 I used to fly changed the neutral
position of the whole flying tail, etc...

Oddly enough, the F-15 is an exception that actually acts the way MXS
thinks - the flight control system is always resetting itself to 1g
(always in trim), so when you slow down, the stick doesn't move. On
takeoff, if you add a forward trim input, you will extend your takeoff
distance since you will get less angular deflection when you pull full
aft stick to rotate. So maybe MXS should get an F-15 addon to MSFS!

MXS, if you really want to learn about changing CG to affect flying
performance, try a gliding sim like Condor (it is supposedly much
better than MSFS anyway). In high performance gliding, we carefully
adjust our CG for minimum trim drag (usually set to 30 - 40 % forward
of the aft CG limit), carry water ballast to go faster, don't have any
trim tabs (springs instead) and in flapped gliders, control speed with
the flaps. That concept should keep you busy for a while!

Finally - MXS, if you want to have enough control authority "just in
case", then set your speed to just under Va (maneuvering speed). That
way, by design, you can pull back on the stick all you want and not
break the plane - faster and you can over-G and bend things; slower and
you will just enter an accelerated stall a bit earlier. And you can
set your trim wherever you want....

Cheers!

Kirk
Ls6-b "66"