THS:
IN FLIGHT
In flight, on all fly-by-wire aircraft, the position of the pitch trim surface
automatically adjusts in order to maintain the flight path with no deflection of the elevators.
The position of the pitch trim surfaces that is required to maintain Flight
Level depends obviously on the center of gravity of the aircraft.
However, it also depends on several other parameters, such as altitude, speed,
aircraft weight and aircraft configuration
Elevator:
If a very small deflection of the elevator causes "a lot of g", the efficiency of the elevator is very high.
The aircraft is considered to be very sensitive to maneuver.
The maneuver point is the CG, for which the elevator is infinitely effective.
The CG must obviously be as far forward from the maneuver point as possible.
This distance is defined by a maneuverability criteria, that determines that
"at least 1 ° of elevator deflection is required to pull 1 g load factor".
This condition defines the aft CG limit in terms of maneuverability.
But the CG must not be too far forward.
The maximum elevator deflection must enable at least the maximum
acceptable load factor (e.g. 2.5 g) to be pulled.
This condition defines the forward CG limit in terms of maneuverability.
Maximum elevator deflection and extern load factor: