Aero Chapter 02, High-Speed Flight
T-45 Aerodynamics Student Workbook
FLIGHT CONTROL SYSTEM
By necessity, flight controls of a transonic or supersonic aircraft are different than those of a subsonic
aircraft. Separation of the boundary layer behind a compression wave will occur as the wave strengthens.
A control surface operating in the area of separated airflow (Figure 33) would be ineffective and not affect
the pressure distribution about the rest of the airfoil. However, with a movable leading edge, either
stabilator or movable horizontal stabilizer with elevators, the area forward of the shock wave will remain
effective and affect pressure distribution about the airfoil (Figure 34).
Ineffective
Effective
Ineffective
Effective
Separation
Separation
Effective
Ineffective
Ineffective
Effective
Separation
Separation
Figure 33: INEFFECTIVE TRANSONIC
Figure 34: EFFECTIVE TRANSONIC
CONTROLS
CONTROLS
Differential stabilizers (Figure 35), similar to those on the F-14 and F-18, provide not only pitching
moments but also rolling moments. The T-45 does not have a differential stabilator system.
The T-45 has irreversible flight control systems powering
ailerons and the stabilator. Aircraft hydraulic systems
magnify the pilot’s commands and permit aircraft control
during high-speed flight. Aerodynamic pressures are not
fed back to the pilot from control surfaces as, for example,
a shock wave forms on the control surface (Figure 36).
No direct feedback between the stick and
control surface. Stick input ports hydraulic fluid
to the actuator effecting control surface
Control stick "feel" is artificial.
IRREVERSIBLE
(NO FEEDBACK FROM CONTROL SURFACES)
Figure 35: DIFFERENTIAL
Figure 36: FULLY POWERED CONTROL SYSTEM
STABILIZERS
(7-99) Original
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