The ailerons, like the other primary flight controls, are monitored for correct
operation by a Hard Over Prevention System (HOPS). The HOPS will shut off
hydraulic pressure to both aileron actuators if aileron movement does not
correspond to flight crew of autopilot commands.
If no hydraulic pressure is available to the aileron actuators, the hydraulic control
valves of the actuators will bypass any residual pressure and full aileron deflection
will be available using manual control inputs from the cockpit yokes. A slower
response time to aileron manual operation can be expected due to the lack of
boost authority and the absence of assist from the flight spoilers (if the spoilers
cannot be hydraulically powered).
2. Description of Subsystems, Units and Components:
A. Aileron Control Linkage:
Rotation of each control yoke produces a parallel rotation of the other yoke
through the mechanical arm beneath the cockpit floor. As both yokes rotate
bellcranks translate rotational movement into linear displacement of the
control cables leading to the hydraulic actuators that move the ailerons.
Integrated into the cable linkage are the autopilot electric servos and a
series of bellcranks and linkages to route the cables around existing
equipment beneath the cabin floor. The aileron cable links transit aft along
the fuselage until reaching the aft bulkheads of the main landing gear
wheel wells. At this point the cables pass though pulleys that translate the
forward and aft motion of the cables ninety degrees (90°) and out the aft
face of each main wing beam. The cable linkages connect to the flight
spoiler mixing and summing links and continue out to the aileron hydraulic
actuators. The hydraulic actuators are located on the aft wing beam
between the flaps and the ailerons. The actuators boost manual or
autopilot control inputs and position the ailerons in the commanded
direction.
Each hydraulic actuator is powered by both hydraulic systems. The
actuators have a central shaft surrounded by a dual piston chamber. Each
chamber is powered by a dedicated left or right hydraulic system. The
pistons are moved by hydraulic pressure ported to the extend or retract
sides of the chamber by control valves moved by the aileron cable linkage.
The pistons extend or retract the central shaft of the actuator that in turn
moves a bellcrank and linkage to position the aileron. A mechanical
linkage, termed a force link, between the control cable input to the actuator
and the output of the actuator to the aileron parallels actuator operation
and provides the sensing element for operation of the HOPS provision.
Loss of a single hydraulic system will not degrade aileron activation since
the remaining system is capable of providing sufficient power for a full
range of aileron displacement. See the illustration of the linkages and
actuators in Figure 11.
B. Aileron Control Disconnect:
If a malfunction causes one of the ailerons to become inoperative, the
mechanical link between the two cockpit control yokes can be separated to
allow independent operation of the normally functioning aileron. A handle
on the right side of the cockpit center pedestal, labelled AIL DISC is
connected to a pin in the mechanical linkage. (See Figure 12). Pulling up
on the handle retracts the pin mating the two yokes and allows full control
of the operative aileron. If the flight crew is unable to exert sufficient force
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-27-00
Page 37
August 14/03
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