Landing Gear & Brakes Flashcards
Explain the PSEMs.
There are two Proximity Sensor Electronic Modules (PSEM).
They process signals from the six weight-on-wheels (WOW) proximity sensors to determine if the plane is airborne or on the ground.
NOTE: Two WOW on each landing gear.
How does landing gear retraction work?
Hydraulic pressure releases for the nose and main landing gear locks,
and pressurizes the respective actuators to retract the landing gear.
Retraction completed? Held in place by uplocks.
How does landing gear extension work?
Hydraulic pressure releases for nose and main gear uplocks,
also for the retraction actuators.
Landing gear doors are mechanically opened.
When extension is completed, the landing gear is locked extended by the downlock springs.
What’s the electrical override switch?
Switch that electronically bypasses the PSEM and commands gear extension.
How does the alternate gear extension handle work? When is it used?
Used when hydraulic pressure is N/A for landing gear operation or the electrical system fails.
When pulled, releases hydraulic pressure in the landing gear lines and mechanically releases all landing gear uplocks.
Gear extends free fall via gravity & aerodynamic forces.
What does the down lock release button do?
Pressing this overrides the WOW protection (lever locked when it thinks its on the ground) and allows the landing gear lever to be moved regardless of WOW sensors.
