Landing Gear Introduction Flashcards
What is the primary function of the aircraft landing gear?
- Maneuvering during ground operations
- Absorb the loads associated with landing and take-off.
What are the different structures that can be used as landing gear?
- Wheels and tyres
- Skis
- Skids
- Floats
What are three types of landing gear installed on fixed wing aircraft?
- Fixed
- Retractable
- Floats/Floating Hull
- Skis/Skids
What are three different types of undercarriage configuration?
- Conventional
- Tricycle
- Tendem
What are some major components of a landing gear system and what are their functions?
1) Shock absorbers - Absorb sudden impact of loads on aircraft landing, mechanical/hydraulic construction designed to convert kinetic energy created into heat via fluid transfer within the unit.
2) Air/Oil Oleo Struts - A more advanced form of shock absorber which accommodates greater loads, contains separate air (nitrogen) and hydraulic fluid compartments
3) Uplocks/Downlocks - mechanicals locks that keep landing gear in their intended position
4) Undercarriage doors
5) Cockpit Indications
6) Hydraulic Accumulator
What are four types of aircraft steering configurations?
1) Rudder Steering - aerodynamic steering from airflow and rudder.
2) Direct Steering - Pilot induced movement of the nosewheel via electrical, mechanical or hydraulic means - normally operated by rudder pedals
3) Differential braking - Asymmetric braking applicated
4) Tiller Steering - small steering wheel in the cockpit.
What are the two main steering components?
- Rudder Pedals/brakes
- Tiller
What are the primary functions of the Weight on Wheels (WOW)/Squat Switch in the aircraft?
1) Indicate the position of the associated landing gear strut upon which it is located
2) Report to cockpit indication system (visual/audio)
3) Prevent inadvertent undercarriage retraction while the aircraft is on the ground by enabling electrical isolation of the retraction control circuit.
What are some alternate methods of lowering the landing gear, should the main system fail?
- Alternate hydraulic supply (redundancy system)
- Stored hydraulic supply (accumulator)
- Compressed air or nitrogen
- Mechanical release
- Electrical release
- Manual-crank
What are some main braking designs?
1) Disk Brakes - hydraulically or pneumatically powered
2) Thrust Reversers
3) Spoilers
4) Drogue/Drag Chute
What is aquaplaning and what are some consequences?
- Traction is lost between the tyre and runway, due to the tyres inability to dissipate the volume of fluid between it and the ground surface.
- Causes an inability to steer or brake
What is partial dynamic aquaplaning?
- Rotating tyre causes hydrodynamic pressure to slowly lift the tyre on the surface
- Only a proportion of traction is available.
- High ground speeds
- Loss of traction, however, when speed decreases, traction increases.
What is full dynamic aquaplaning?
- The tyre fully lifts from the surface
- Depends on stationary/rotating wheel and the pressure of the tyre.
What is viscous aquaplaning?
Oil or accumulated rubber combines with water on a runway to create an impenetrable layer of liquid that the tyres can’t break through.
What is reverted rubber aquaplaning?
On a damp runway with no visible water and is similar to a dry skid.
What are some methods to avoid aquaplaning?
- Porous/grooved runways
- Tyre tread type and depth can also reduce aquaplaning.
- Piloting techniques which call for a firm touchdown onto wet runways to allow the tyre to penetrate the water and begin the braking action.
What is the purpose of anti-ski systems?
To mitigate aquaplaning, skidding or excessive braking.
What are some advantages of anti-ski systems?
1) Increases in control during instances of low traction
2) Reduction of tyre blow-outs due to skidding
3) Pilot input is minimized during sequences of adverse conditions
4) Alternate traction control technology for more complex system
What are main materials used in wheel construction?
- Aluminium
- Magnesium alloy
What are the two major wheel designs?
- Two Piece
- Removable flange
What are fusible plugs?
- Prevention of failure of tyres cause by excessive heat.
- Small plug of alloy that will melt at a pre-designed temperature allowing the deflation of a tyre in a benign manner.
What are some common causes of wheel damage/failure?
- Over/under inflation of tyres
- Corrosion
- Excessive brake heat
- Heavy landing
What are two main tyre classifications?
- Tube
- Tubeless
What are all tyres marked to indicate?
- Size
- Speed rating
- Ply rating
- Tubed or tubeless
What are tyres inflated to high pressures?
- To increase rigidity against the sidewall
- Enable greater resistance to tyre deformation
What gas are aircraft tyres filled with? Why?
- Nitrogen
- Nitrogen has a greater resistance to the expansion/contraction cause by temperature variance
- Increased fire resistance due to the reduce amount of oxygen available
- Nitrogen diffuses through rubber at a slower rate than oxygen
- Increases tyre life due to decreased risk of blowout
