LESSON: Landing Gear System

5-A 3 Landing Gear

OBJECTIVE: To develop the students understanding of the landing gear system and associated equipment (BE-76 specific)

ELEMENTS: Elements of Landing gear system  Control Switch  Position Indicators  Time-delay Relay  Safety Retraction Switch  Warning Horn  Operation  System Malfunctions

STUDENTS ACTIONS:  Listen, take notes, ask questions  Respond to instructors questions  Leave with a framework understanding of the subject

INSTRUCTORS ACTIONS  Discuss lesson objective  Introduce the various flight instruments  Discuss each of the landing gear components individually  Describe their operation and use  Ask pertinent questions to determine students understanding  Assign appropriate study material

COMPLETEION STANDARDS: The student should demonstrate adequate understanding of the landing gear system and associated equipment by: successfully completing an oral quiz or written exam

1 5-A 3 Landing Gear

INTRODUCTION Attention/Motivation An understanding of the landing gear system and associated equipment of the aircraft you fly is important for proper operation and dealing with and resolving problems. Overview This lesson will discuss elements of, landing gear system and associated equipment

DEVELOPMENT

General Description  Retractable tricycle gear  Fabricated from magnesium castings and aluminum castings  Retraction/extension is electrically driven hydraulically actuated

Control Switch  Controlled by a two position switch Up/Down  Switch must be pulled out of the safety detent before it can be moved to the opposite position  Control switch controls reversible DC electric motor/hydraulic pump (hydraulic powerpack)

Position Indicators  Three green lights, one for each gear, become illuminated when the respective gear is down and in the locked position  A red light illuminates any time the gear is in transit or in an intermediate position  No lights will be illuminated when the gear is in the up position  Pushing the lights in will verify the lights are functional  Twisting the light will control its intensity

Time-delay Relay  Protects the pump motor  Will automatically disengage the pump motor after 30 seconds of continuos operation  Reset by putting the gear lever in the Down position

Safety Retraction Switch  Prevents inadvertent retraction of the landing gear  Safety pressure switch installed in the pitot system  Deactivates the electric pump circuit when the ram air pressure is below 59-63 knots  Important not to rely on the safety switch to keep the gear down during taxi and takeoff

Warning Horn  Alerts the pilot that the gear is not down and locked  Sounds any time any of the gear is not down and locked and either throttle is reduced to 12” of MP or less and/or the flaps are lowered beyond 16º

Operation  Retraction 1. Gear handle is placed in the up position 2. Logic circuit checks the Safety Retraction Switch 3. If airspeed exceeds 61 ±2 KTS. the Hydraulic power pack runs in the up direction 4. Red In-transit light illuminates 5. The Hydraulic actuators on each of the gears’ swing the over-center locks open and drive the gear up, holding it in the up position 6. Each gear reaches it’s upper limit of travel in the wheel-well, and hydraulic pressure starts to build 7. Once hydraulic pressure reaches 1550 PSI a Pressure switch sends a signal to the gear logic circuit and the Hydraulic power pack stops 8. Gear up is confirmed when the In-transit light turns off

 Repressurization Cycles 1. Due to actuator bypass, hydraulic pressure gradually diminishes 2. When pressure falls below 1250 PSI the Pressure switch sends a signal to the gear logic circuit and the Hydraulic power pack runs and restores the system to 1550 PSI 3. May occur approximately 4-5 times per hour 4. Normally repressurization cycles last only a few seconds and are indicated by a momentary In-transit light illumination

 Extension 1. Gear handle is placed in the down position 2. Hydraulic power pack runs in the down direction depressurizing the system 3. Red In-transit light illuminates 4. The Hydraulic actuators assist gravity and Over center lock springs to swing the over-center locks closed moving the gear to the down and locked position 5. Each over-center lock has a micro switch that sends a signal to the logic circuit when the over-center lock is in the proper position 6. The gear logic circuit illuminates the corresponding green gear Position Indicator lights once each individual gear is down and locked

System Malfunctions  Loss of hydraulic fluid 1. Excessive/continuos Hydraulic power pack operation 2. Hydraulic power pack may overheat and trip Gear Motor circuit breaker 3. Place and leave gear in the down position  Excessive actuator bypass 1. Excessive/continuos Hydraulic power pack operation 2. Hydraulic power pack may overheat and trip Gear Motor circuit breaker 3. Place and leave gear in the down position

 Emergency Extension 1. Pull out the gear motor circuit breaker 2. Place the Gear handle in the down position 3. Slow to 100 KTS or less 4. Turn Emergency extension valve 90º counter clockwise using the emergency extension wrench. This connects the two sides of the hydraulic actuators together and bypasses the Hydraulic power pack 5. No hydraulic pressure is needed to move the gear to the down and locked position

CONCLUSION