7-4-3
Electromechanical Actuators
7-4-3.1
Description
Both nose landing gear and main landing gear actuators have the same functionality and are
electromechanical, self-rigging type actuators. The actuator motor control and monitoring
electronics are incorporated within the actuator. Control is provided by the landing gear
selector handle and the landing gear control system (including the Gear Relay Unit).
The actuator consists of an electric motor connected to a series of gears which reduce speed.
The gear train has a thrust bearing connected to a ball screw and shaft. The ball screw
transforms the rotation of the gear to the linear movement necessary to extend and retract the
landing gear.
The motor brake is engaged when actuator movement is stopped.
An emergency gear extension system is a cable-operated system to disengage the gear train
from the electric motor. Once initiated, the emergency free fall is damped by a centrifugal
brake within the actuator to avoid damage to the structure.
Electrical power supply for the actuators is provided from the SECONDARY POWER LINE.
Power is applied to the actuators for 30 seconds following gear handle movement.
Cockpit controls consist of the following:
−
A landing gear selector handle is located on the pilot's lower right panel and facilitates
extension or retraction of the landing gear. It activates up and down switches situated
directly on the handle system. The handle is equipped with an electrical spring loaded
solenoid which prevents it from moving to the retracted position when the airplane is on
the ground. The airplane on ground status is sensed by the MAU
−
An emergency gear extension (release cable) system, actuated with a handle, located at
the rear of the center console, is used to disengage the gear train in the actuator and
enables emergency free fall of the landing gear if the electric drive system fails.
7-4-3.2
Operation
When the landing gear handle is set to the up (or down) position a command signal is sent to
the actuator to move to the retracted/extended position. At the same time the actuators are
powered for 30 seconds.
The main and nose landing gears are held in its extended position by an overcenter two piece
drag link and an overcenter spring.
The actuators are of the linear type with the main landing gear actuators also incorporating the
down locking mechanism.
7-4-4
Indication/Warning
Extended position indication is provided by micro switches situated at the main landing gear
drag link and a proximity switch on the nose landing gear door. Retraction position indication is
provided by proximity switches on the main and nose landing gear doors.
Landing gear position is shown by three icons (one for each gear) in the GEAR window of the
systems MFD. Each icon can show gear displays for various conditions (refer to
).
Section 7 - Airplane and Systems Description
Electromechanical Actuators
Pilot's Operating Handbook
Report No: 02406
Issue date: Mar 06, 2020
Page 7-4-2
12-C-A15-00-0704-00A-043A-A
FOR
GENERAL
AND
FAMILIARIZATION
PURPOSES
ONLY
