Landing Gear and Brakes Flashcards
List the requirements for the landing gear of a multi-engine jet A/C
For land-based aircraft, the undercarriage must provide a safe, reliable and serviceable means to:
- Support aircraft on the ground at MAUW.
- Absorb landing loads and provide shock absorption moving over ground.
- Withstand side loads.
- Minimum rolling friction.
- Minimum drag when airborne.
- Traction for braking.
- Protection from inadvertent retraction on the ground.
- Minimum weight for strength.
List the components of the bogie
- Pivot trunnion and trunnion beam
- Upper and lower side brace
- Torque arms
- Tubular “H” member
- Pivot fork and shaft
- Equaliser
- Positioner
- Shock strut
- Drag brace
- Upper outer cylinder
- Lower inner cylinder
- Axle
What is the function of a pivot trunnion and trunnion beam?
- Pivot trunnion: the anchor to the structure of the bogie.
- Trunnion beam: allows pivot trunnion to pivot to retract
What is the function of the upper side brace and lower side brace?
Supports the gear laterally eg. when landing during crosswinds, it will absorb the load (sideloading).
What are the functions of the torque arms?
- To keep the pistons and wheels aligned.
- One end of the links is attached to the fixed upper cylinder.
- The other end is attached to the lower cylinder (piston), so it can’t rotate, keeping the wheel aligned.
- Essentially maintain fore and aft alignment of the bogie
What is the function of the pivot fork and shaft?
- Is a big shaft through the centre, 4 axles for the wheel.
- Pivot fork is a pivot that joins the tubular h member to the centre strut.
- Essentially is just a pivot that allows the H member to move.
What is the function of the equaliser?
Acts with the positioner by ensuring that the wheels are in the correct position at all times by maintaining an angle of which that the rear wheels are down and front wheels are up.
What is the function of the positioner?
Hydraulic ram to set the pivot beam angle.
What is the function of the shock strut?
- Uses compressed air or nitrogen combined with hydraulic fluid to absorb and dissipate shock loads.
- Sometimes referred to as an oleo strut.
- Shock strut is constructed of two telescoping cylinders or tubes that are closed on the external ends.
What is the function of the drag brace?
- The opposite side to the side brace, which is at the fore and aft of the aircraft, supports the gear and stops it from folding back.
- Perpendicular to the side brace. Acts in the longitudinal axis.
What is the function of the upper cylinder?
- Fixed to the aircraft and does not move.
What is the function of the lower cylinder?
Called the piston and is free to slide in and out of the upper cylinder.
Explain nose-wheel steering with regards to large aircraft?
- Utilises a small steering wheel. Also called the ‘tiller’.
- Activates a hydraulic actuator, either through a system of cables and pulleys, electrical servos and synchros or digital data transmission as in fly-by-wire-technology.
Explain nose-wheel steering with regards to light aircraft?
- Utilises rudder pedals.
- Rudder pedal has a push rod that connects to the nose wheels.
- Rudder pedals function when you taxi.
Describe the principle of operation of a power brake system?
- Almost all large aircraft have brakes operated by pressure from the main hydraulic (or pneumatic) system.
- The brake pedals are connected to brake control valves, which regulate the pressure passed to the wheel brake units in proportion to the force the pilot applies to the pedals.
- A check valve and accumulator hold pressure for the brake system in the event of hydraulics failure.
- There will also be a further back-up in the form o an emergency bottle of compressed air or nitrogen, which can be used if necessary to pressurise the fluid in the brake system.
