Landing Gear Flashcards
A/c l/d gear layout and config
Categorised according to the posn of the subsidiary wheel
Disadv of a taildragger/tailwheel
High drag on t/o
Can over brake
Adv of a tricycle undercarriage
Better cockpit vis Easier to control on especially in x winds Less likely to nose over Braking is more straight fwd Less drag on t/o
Common types of l/d gear
Spring steel leg
Cantilever - supported at 1 end only
Rubber cord or bungee
Oleo- pneumatic struts
Torque links
Found on oleo-pneumatic l/d gear - stops the main plunger tube rotating inside the leg
% of weight on nose gear
10%
% of weight on main gear
90%
Definition of bogies
4 or more wheels on a bogey beam
Could also be called truck or set
Typical main wheel arrangements
Single
Tandem
Double
Bogie
Main disadvantage of a bogie
Large footprint of a bogie unit will cause the unit to crab whilst turning
Main types of wheel attachment
Cantilever - for light a/c
Forked, Half forked - stronger, for heavier a/c
Dual - load spread over 2 wheels
% of shock absorbed by shock absorbers
90%
Oleo pneumatic the use of nitrogen gas
In the main plunger - acts as a spring to absorb the loads
Oleo pneumatic- oil
In the main body to dampen the spring action
Oleo pneumatic - most likely cause for the fescalised portion being too small is
The shiny bit
Low gas n2 pressure
Could result in bottoming-out on l/d
Oleo pneumatic - oil
If oil levels are too low the rebound is not properly damped
Purpose of the shortening mechanism
Shortens/lengthens the gear on retraction/extension
Brake bars
Torque limiting - torque links sends a message to the braking system about heavy braking - prevents wheel leg bending
An example of an additional load on the l/d gear
Towing = shear
Creep - l/d gear
Unwanted movement of the screw jack - req a mechanical lock to prevent this on screwjack l/d gear
Automatic self centring
Ensures the nose wheel is centred before it is retracted - needs to be for extension/retraction
Castering
Allow stejering by differential braking
Downlocks on l/d gear
Ensures that accidental retraction can’t occur
Over centred geometric device
Used to lock gear down
Retraction and extension is completed by
Selector valves
The edge of the l/d gear door is
Frangible
Solenoid latch
Prevents YOU from moving the gear lever while on the ground
Info is sent through from the air/ground logic circuits - weight on wheels
OFF posn on the l/d gear lever
Stops the pressuring of the gear system during flight
When does the l/d gear warning horn activate
A/c is in the l/d config and 1 or more throttle levers are less than approximately 1/3rd open
Continuous horn for l/d
Interment horn for t/o
VLE and VLO
VLE = max speed with the l/d extended
VLO = max operating speed for the l/d gear - doors become the limiting factor
The tiller can steer the nose wheel
75* left or right
May be supplemented by body gear steering which reduces the tyre damage caused by scrubbing
Shimmy definition
Rapid sinusoidal oscillation of the nosewheel and is divergent in nature
Possible causes of shimmy
Uneven tyre pressure Unevenly worn tyres Unbalanced wheels Worn shimmy damper or wheel bearings Worn torque link will make things worst
How to reduce shimmy
Hydraulic damper fitted
Heavy self centring springs
Double nose wheels
Twin contact tyres - maarstrand twin contact tyre
