MD-11 Flight Crew Operations Manual
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Flight Controls -
Description and Operation
Flt.10.4
Spoiler System
Five spoiler panels are provided on the upper surface of each wing to assist aileron
lateral control, reduce speed during flight, and spoil lift for increased brake
efficiency. Each spoiler panel is individually powered by one of the three
hydraulic systems. All hydraulic systems are required for full spoiler operation.
When used to assist lateral control, the system extends all five spoiler panels on
one wing, to a maximum of about 60 degrees from faired, while maintaining the
opposite wing panels retracted. When used as speed brakes for slowdown and
emergency descent, the system symmetrically extends all panels simultaneously
on both wings, to a maximum of about 30 degrees from faired. With flaps retracted
during flight, the spoilers can be manually deployed to a maximum of 30 degrees.
When both functions are used at the same time, the panel extension for speed
brake function is a maximum 60 degrees on one wing. On the other wing, lateral
control panel extension is subtracted from the speed brake panel extension to
retract those panels. Flight spoilers, when used as speed brakes or when deployed
as ground spoilers retain lateral control differential motion capability.
Spoiler system lateral control assist is active in all modes, extending all spoilers
on the downward moving wing in proportion to control wheel movement. All five
flight spoilers on each wing are used for lateral control over the flight speed range.
The spoiler handle does not move.
An inoperative cable system servo or spoiler actuator can be overridden by pilot
force to maintain control over the remaining active portions of the system. Spoiler
up-float, in the event of a hydraulic failure, is prevented by a hold-down check
valve in the spoiler actuator valve manifold.
Spoiler/speed brake extension and retraction is controlled by the position of the
SPOILER handle. The SPOILER handle consists of a T-handle with a latch.
Detents in the pedestal allow latching at the RET, 1/3, 2/3, and FULL positions.
At the FULL position, a positive (lower) gate prevents further spoiler deployment.
This gate, at full speed brake (half ground spoiler) deflection protects against
exceeding allowable wing stress levels during flight. The latch is disengaged by
squeezing the T-handle or by lifting the handle upward into the ARM position.
The pilot cannot manually deploy symmetrical spoilers with flaps extended 5
degrees or more, except with the autospoiler in transit or the nose gear strut
compressed. The maximum available manual spoilers under these conditions is 60
degrees.
With speed brakes deployed and flaps extended, the RETRACT SPD BRK alert
is displayed. With flaps or speed brakes retracted, the alert is not displayed.
October 02, 2006
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