Landing Gear Flashcards
How is the landing gear operated?
Hydraulically operated, electrically powered
Ie) electrical valves to control hydraulic actuators
What kind of suspension is on the gear?
Oleo, will compress quick but expand slow
What components make up the hydraulic system and where is it located?
Hydraulic control block: • Electric motor • Hydraulic pump & pressure switch • Hydraulic reservoir • Hydraulic accumulator Located rear of aft cockpit bulkhead, left side
Which way does the landing gear retract?
Nose, forwards
Main gear, inboard
How is the landing gear kept retracted?
The system is always pressurised. Hydraulic pressure on actuators keep pressure on to lock gear in retracted position.
Difference between px relief valve and regulator valve?
Regulator valve keeps pressure to normal 1800PSI, whereas the receiver valve is in case of regulator failure and limits to max 2600PSI.
Both located in hydraulic control block.
What does the accumulator do?
Dampens the pressure changes
How many and what purpose are the solenoid valves?
One controls supply the other return of the flow to the actuators.
Located in hydraulic control block.
What purpose is the regulating valves?
So gear extends at similar rates.
There is a regulating valve in the ‘extend’ return line which controls fluid flow from actuators.
How does emergency extension work?
What is the max speed?
When the emergency lever is pulled, return fluid from actuator bypasses the regulator valves.
Micro switch at emergency extension valve isolates power from hydraulic pump when in emergency position.
Max speed 156kt
What will happen to the landing gear if an electrical failure was to occur?
It would automatically extend.
What do the squat switches do on gear of the landing gear?
Nose (x4): up, down x2, pressure
Left (x3): up, down, WOW
Right (x3): up, down, stall warning heat derated 50%
What do the power switches do?
If both throttles are moved to the closed position, at approx 14” the switches close. If at this point the landing gear is not extended with or without flap a horn will sound.
What ways will the gear horn sound?
Test button
Below 14” and no gear
Landing flap with no gear
How does the steering system link to the wheel on the ground?
A universal coupling joint attaches the 2 systems together
How does the centring system work?
On the ground, a piston is constantly pushing down onto a valley shaped device, so as rudders are released, the roller moves back to the centre.
How does retractions work (differential and full pressure)?
When the lever is moved to retract, the solenoid valve will move to allow fluid from ‘extend’ to ‘retract’ side. The electric pump will pump to maintain system normal pressure of 1400-1650PSI if px drops below 1400PSI. As the effective surface area of the retract side is greater than the extend, there is a differential pressure and will begin the initial retraction.
Fluid from the extend side flows through regulator valves to reservoir, when the extend solenoid valve is set to full pressure position.
The pump then apples pressure to the retract side until pressure rises indicating that the system is retracted. The accumulator will hold the system pressure without the pump operating.
How does gear extension work?
The retract side of actuator deenergises and allows flow through regulating valves to reservoir.
The extend solenoid valve energises fluid to flow through extend valves to the extend side of actuator.
Once extended, folding stays spring lock into place and the system will continue to pressurise until 1650PSI.
