Topic 3: Aircraft Landing Gear Flashcards
The functions of the landing gear are:
- To provide a means of maneuvering
the aircraft on the ground. - To support the aircraft at a convenient
height to give clearance for propellers
and to facilitate loading. - To absorb the kinetic energy of landing
and provide a means of controlling
deceleration.
this provides a means of maneuvering
the aircraft on the ground.
landing gear
this supports the aircraft at a convenient
height to give clearance for propellers
and to facilitate loading.
landing gear
this absorbs the kinetic energy of landing
and provide a means of controlling
deceleration.
landing gear
landing gear layout
- tricycle layout
- tailwheel or taildragger
this landing gear layout has its nose wheel unit forward of two main gear units.
tricycle layout
this landing gear layout has a tail wheel behind the main wheels.
tailwheel or taildragger
landing gear types:
- fixed (non-retractable) landing gear
- retractable landing gear
With slow, light aircraft, and some larger
aircraft on which simplicity is of prime
importance, this is often fitted.
fixed (non-retractable) landing
gear
In this landing gear type, the reduced performance caused by the drag of the landing gear during flight is offset by the simplicity, reduced maintenance, and low initial cost.
fixed (non-retractable) landing gear
With higher performance aircraft, drag
becomes progressively more important, and this is retracted into the wings or fuselage during flight.
retractable landing gear
Its penalties include increased weight, greater
complication, and additional maintenance.
retractable landing gear
3 main types of fixed landing gear:
- spring steel leg
- rubber cord (shock absorber)
- oleo-pneumatic struts
these are usually employed at the main
undercarriage positions.
spring steel legs
The leg consists of a tube, or strip of
tapered spring steel.
spring steel leg
The upper end is attached by bolts to the fuselage and the lower end terminating in an axle on which the wheel and brake are
assembled.
spring steel leg
when used as a shock-absorber, the undercarriage is usually in the form of tubular struts, designed and installed so that the landing force is directed against a number of turns of rubber in the form of a grommet or loop.
rubber cord
some fixed main undercarriages, and most fixed nose undercarriages, are fitted with this
oleo-pneumatic shock absorber strut
one point worthy of consideration is the fitting of spats to this.
oleo-pneumatic strut
are an aerodynamic fairing which may be required to minimize the drag of the landing gear structure.
spats
consists of two concentric cylinders, one free to slide inside the other.
a simple oleo-pneumatic strut
Its cylinders are filled with hydraulic fluid and gas which are kept apart by a separator piston.
oleo-pneumatic strut
its outer or upper cylinder is attached to the airframe structure and houses the inner or lower cylinder and a piston assembly.
oleo-pneumatic strut
its wheels and axle are connected to the bottom of the inner cylinder
oleo-pneumatic strut
Its inner cylinder is free to rotate and move up and down within the outer cylinder
oleo-pneumatic strut
rotary movement and up and down movement is limited by this which connect the inner and outer cylinders together
torque links
also called torsion or scissor links
torque links
landing gear is subjected to torsion loads during ground maneuvering and these loads are taken by the _____________
torque links
landing gear is subject to this during ground maneuvering
torsion loads
the smaller the radius of turn, the greater will be the load felt by the ___________ so all turns should be made as wide as possible.
torque links
the __________ the radius of turn, the __________ will be the load felt by the torque links so all turns should be made as wide as possible.
smaller; greater
in the operation of oleo-pneumatic struts, the area on the outer cylinder is filled with __________ and the area on the inner cylinder is filled with compressed gas which may be either __________ or ___________.
hydraulic fluid; air; nitrogen
in the operation of oleo-pneumatic struts, this is a free-floating piston which keeps the fluid and gas apart.
separator piston
in the operation of oleo-pneumatic struts, the _________ supports the _________ of the aircraft on the ground, __________ during taxiing, and absorbs the ___________ on landing.
gas; weight; cushion bumps; shock
in the operation of oleo-pneumatic struts, its purpose is to dampen oscillations and control the rate of compression and extension of the cylinders.
hydraulic fluid
in the operation of oleo-pneumatic struts, the _________ connected to the lower cylinder has _________ in it which restricts the flow of fluid through the piston, thus, dampening the movement between the cylinders.
piston; holes
in the operation of oleo-pneumatic struts, this component is fitted to the lower cylinder piston assembly.
flutter valve
in the operation of oleo-pneumatic struts, this consists of a free-floating circular plate with a large central hole and is free to move up and down within its housing.
flutter valve
in the operation of oleo-pneumatic struts, on the top of the inner cylinder, there is a small ________ plus a ________ around the perimeter
central orifice; series of holes
when this happens in the operation of oleo-pneumatic struts, the plate will be pushed up with it, blocking off the outer holes and allowing a limited flow only through the central orifice.
fluid is flowing upwards (strut extending)
when this happens in the operation of oleo-pneumatic struts, the plate will be pushed down allowing a greater flow of fluid through all of the holes
fluid is flowing downwards (strut contracting)
in the operation of oleo-pneumatic struts, the ________ limits the rate of movement, ________ restriction when extending, and ________ restriction when contracting
flutter valve; more; less
when an aircraft is stationary on the ground, the _______ will support the weight of the aircraft with the lower cylinder approximately on the _______ of its stroke.
gas pressure; midway
during taxiing, bumps are cushioned by the _______ and dampened by the _______ through the orifice.
gas pressure; limited flow of fluid
during takeoff, this will cause the lower part of the leg to extend to its fullest extent
gas pressure
during landing, the _______ shortens and the _______ is forced through the flutter valve.
strut; fluid
as the downward force of the landing decreases, this acts as a spring and extends the strut
gas pressure
as the downward force of the landing decreases, the _______ will move with the fluid flow blocking off the outer holes and further reducing the speed of upward movement of the upper cylinder, thus, helping to prevent a bounce on landing.
flutter valve plate
wheels to leg construction:
- fork
- half fork
- cantilever
- dual wheel
- multiwheel (bogie connected)
employed to improve aircraft performance by reducing drag
retractable landing gear
also provided with mechanical locks to ensure that each undercarriage is locked securely in the retracted and extended positions.
retractable landing gear
retractable landing gear is also provided with _________ to ensure that each undercarriage is locked securely in the retracted and extended positions.
mechanical locks
this also has devices present to indicate to the crew the position of each undercarriage
retractable landing gear
manual means are installed by which it can be extended in the event of failure of the power source.
retractable landing gear
systems are provided to this to prevent retraction with the aircraft on the ground.
retractable landing gear
it has warning devices installed to guard against landing with the landing gear retracted.
retractable landing gear
in the designing and construction of retractable landing gear, the ________ and ________ of undercarriage units on aircraft is by no means standard.
geometrical arrangement and physical location
in the designing and construction of retractable landing gear, the type, size and position are decided at the _______, having already taken into account the many factors that must be considered.
design stage
in the designing and construction of retractable landing gear, most aircraft use the ________, where the two main undercarriage units are positioned just aft of the center of gravity and support up to ________ of the aircraft’s weight and all initial landing shocks.
tricycle layout; 90%
in the designing and construction of retractable landing gear, the leg is attached to the wing spars by a ________ or ________ on which the leg is free to rotate laterally.
cylindrical beam; trunnion
in the designing and construction of retractable landing gear, the upper part of the leg forms the outer cylinder of the _______.
oleo-pneumatic strut
in the designing and construction of retractable landing gear, the strut inner cylinder is connected to the _______ or _______.
wheel bogie; truck beam
The ________ is able to pivot about its central point in a controlled way. There is an ________ connected to a pair of break wheels at each end of the truck beam.
truck beam; axle