OPERATIONS MANUAL

Flight Controls
Elevator Control:
The pilots’ control columns are mechanically interconnected with each
other on the flight deck. Two cable loops mechanically transfer the
joined column motion to hydraulic power control packages (PCPs)
located in the tail of the aircraft. The PCPs provide the variable hydraulic
power to move the elevator surfaces. Also located in the tail are the
autopilot actuators; they too provide mechanical inputs to the PCPs, and
at the same time move the control columns on the flight deck via the
cable loops.
An elevator feel unit in the aircraft tail provides a centering force and
artificial feel to the elevator control system. The feel system is controlled
by the elevator feel computer. The commanded centering force is a
function of the current equivalent airspeed (EAS) and—indirectly—the
center of gravity (CG) which is derived from the stabilizer trim setting:
the computer assumes the CG to be the more aft, the farther the trim is
set nose down. The aerodynamic effect of the elevator is more dominant
when the CG is more aft; hence, to prevent excessive pilot inputs, the
computer increases the centering force accordingly. The same principle
applies when the EAS increases. The feel function is fully operative when
hydraulic system 2 or 3 is pressurized. When both hydraulic systems fail,
mechanical springs provide a constant centering force.
SYSTEM
ANALYSIS
In the simulator, the current elevator feel pressure is indicated on Instructor
> Analysis > Miscellaneous. The value is also accessible through the
simulator’s main network if the checkbox Send elevator feel data is selected
on Instructor > Preferences > Basics.
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