MD-11 Flight Crew Operations Manual
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Landing Gear and Brakes -
Description and Operation
Land.10.2
Trim cylinders maintain the truck beams perpendicular to the main gear struts. A
trim cylinder interlock mechanism prevents moving the GEAR handle up in the
event of hydraulic failure in the trim system.
Nose Gear Steering
Nose gear steering is powered by hydraulic systems 1 and 3. The nose gear
steering wheel and rudder pedals provide steering control. The nose gear steering
wheel has override authority over the rudder pedal steering.
Maximum steering angle using the nose gear steering wheel is 70 degrees either
side of center. Full rudder pedal travel provides steering to a maximum of 10
degrees either side of neutral.
If hydraulic system 1 or 3 fails completely, nosewheel steering is limited to 25
degrees in the direction of the inoperative system. Rudder pedal steering is not
affected noticeably by loss of one hydraulic system.
Rudder pedal steering is rendered inoperative by the mechanical ground sensing
mechanism during nose gear strut extension at takeoff.
Nose gear steering using the nose gear steering wheel while the gear is retracted
is not possible as the steering bypass valve is mechanically placed in a bypass
mode upon nose gear retraction. This prevents inadvertent steering and possible
jamming of the nose wheels in the nose wheelwell.
Ground Sensing System
A mechanically operated ground sensing mechanism is installed. It is operated by
extension and compression of the nose gear strut.
The system does the following:
• Mechanically disables rudder pedal nose gear steering.
• Releases the GEAR handle anti-retract lock.
• Activates flight or ground mode for various systems.
When the ground sensing mechanism does not shift to flight mode, the following
systems are affected:
• Takeoff warning system will remain active.
• Pressurization will not function in automatic.
• Airborne engine thrust reverse possible.
• Stall warning, stickshakers, and auto slats will not function.
• Pitot and angle-of-attack heat stays low.
• Airfoil anti-ice inoperative.
• Spoilers have unrestricted operation.
• Autoflight system limited to TO function.
October 02, 2006
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