BOMBARDIER BD-100-1A10, Operating Manual

Page: 443 / 544

LANDING GEAR
Sep 13/2004 Flight Crew Operating Manual Volume 2
REV 1 CSP 100-6
15-01-09
LANDING GEAR (CONT)
NORMAL EXTENSION AND RETRACTION
Normal retraction and extension of the landing gear is initiated by selecting the landing gear switch UP or DN. The retrac-
tion or extension signal is sent to the PSS which monitors various landing gear proximity sensors and weight on wheels
(WOW) inputs. If the correct parameters are met, the proximity system electronic unit (PSEU) energizes the selector valve
to retract or extend the landing gear using the left hydraulic system.
GEAR EXTENSION
During gear extension, the NLG extends rearward and the MLG extends outward.
When the landing gear switch is manually selected to the DN position, the PSEU commands and monitors the following
events:
- Landing gear selector valve is energized to direct hydraulic fluid to release the MLG uplocks and the nose over-
center mechanism, extending the landing gear
- NLG and MLG downlocks are hydraulically and mechanically engaged to secure the landing gear in the extended
position.
GEAR RETRACTION
During retraction, the nose gear retracts forward and the main gear retracts inward.
During landing gear retraction (no WOW signal), the PSEU commands and monitors the following events:
- Landing gear selector valve is energized to direct hydraulic fluid to release the respective downlocks and retract
the NLG and MLG. The brake control unit (BCU) commands a brake pressure of 350 psi for four seconds during
gear retraction to ensure the main wheels have stopped spinning as they enter the MLG bay.
- When the gear is fully up, uplocks for the MLG are engaged mechanically. The uplock mechanism consists of a
housing bolted to the airframe structure containing a latch lever and hook that engages a roller attached to the
steering cuff of the landing gear. The hook holds the NLG in the retracted position.
- A restrictor is located in the aft of the NLG wheel well. This restrictor is installed in the up hydraulic line. When
the landing gear selector handle is selected UP, this restrictor will decrease hydraulic fluid flow which decreases
the retraction speed and allows the NLG to retract smoothly and with less noise.