Studied by 2 people
why is tricycle-type gear preferable over tailwheel-type gear?
Tailwheel aircraft are susceptible to ground loop; the phenomenon where the tail wheel loops around and causes the aircraft to spin on the runway.
also, you cant see as well OR steer as easily with a tail wheel aircraft
List the two types of drag aircraft face?
Induced Drag
Parasitic Drag
Define Induced Drag.
drag caused by the production of lift
Define Parasitic Drag.
Drag produced by the friction of airflow over the structure
What do “wheel pants” do?
Used to decrease wind resistance of fixed wing landing gear, AKA wheel fairings.
List the 4 types of landing gear, including which ones are shock absorbing and which ones are not.
Spring Steel and Composites
Rigid Gear
Bungee Cord
Shock Struts (only this one is shock absorbing)
How do Spring Steel and Composite landing gear systems work?
Type of landing gear taht does not absorb landing shocks but rather accepts the energy in the gear and returns it at a rate and time that the aircraft can handle
Think about the 172, the metal gear “legs” act like a spring
How do Rigid Gear landing gear systems work?
Mainly used by helicopters, requires a very soft landing.
How does a Bungee Cord landing gear system work?
Rubber cushions shock the landing, typically in the form of rubber bungee cords.
How does a shock strut landing gear system work? (be basic, more detailed explanation will come later)
Most widely used, works by a cylinder (attached to the airframe) which accepts a piston (attached to the wheel assy) to slide into it. this piston, free to move up and down in the cylinder, moves up and down and its movement is dampened by the rate at which fluid in the piston can flow through a metering pin oriface.
What is another name for an air-oil shock absorber?
oleo strut
HOw dos an oleo strut work?
The oleo strut absorbs the landing impact as oil transfers from the oil chamber into the air chamber around the tapered metering pin.
what is the typical specification used to determine if a strut is properly serviced?
The length of the piston tube exposed when the aircraft is normally loaded.
“almost all modern aircraft wheels are constructed of ___-_____ _____”
almost all modern aircraft wheels are constructed of two-piece units
What are aircraft wheels typically contructed of?
Aluminum or Magnesium
what is the purpose of a fusible plug?
why shouldnt you spin bearings as you dry them?
Bearing balls/rollers could fly out and kill ya
What sort of damage could you see when inspecting bearings for internal damage?
Intergranular corrosion — Water marks on the internal surfaces of the bearings
Spalling — Slight chipping of the rolling surface of the bearing
How should bearings be packed with grease?
Using pressure packing equipment that pumps grease into all internal parts of the bearing.
by smacking the bearing into grease you have put in the palm of your hand.
Why cant the bead area of a wheel be inspected using penetrant?
the cracks may close up so tightly that penetrant cannot enter the crack.
Define/explain the purpose of a shimmy damper
A shimmy damper is a small piston-type hydraulic cylinder that control the bleed of fluid between the two sides of the piston. The restricted flow prevents rapid movement of the piston (AKA Shimmy) but does not effect normal steering
Explain the basics for a large aircraft nose wheel steering system
A Tiller is used by the pilot to control a steering control valve, which directs fluid into one or another hydraulic steering cylinders on the nose wheel shock strut.
Define Camber
The measure of the amount the wheel leans, as viewed from straight ahead
What must all aircraft with a retractable landing gear system have?
A means of lowering the gear if the primary method of lowering the gear fails
What is a squat switch? What does it do?
AKA a weight on wheels switch, a switch that is triggered when weight is put on the landing gear assy, indicating that the aircraft is on the ground
What is the purpose of landing gear safety pins?
To lock the gear in the down position and prevent them from retracting on the ground.
Define/explain what a center cam is.
A device that is used to center a nosewheel when weight is lifted off of the landing gear.
What is the purpose of having retracting gear?
To reduce parasitic drag.
what is sintering?
a process in which heat and pressure weld the bowdered metal together and to the backing plate.
Define/explain the purpose of a shimmy damper
A 2 chambered piston is mounted to the nose wheel of an aircraft in order to reduce any osciliations/vibrations that occur on the ground.
Explain what is meant by brake bleeding
ON TEST FS
bleeding the brakes describes the process by which a technician cycles brake fluid through the braking system lines in order to eliminate any air in the system, which may cause sponginess in the brake operation.
What is the purpose of automatic brake adjusters?
to compensate for disc wear each time the brake is applied, which eliminates the need for manual brake adjustment.
How do multiple disc brakes work?
a stack of discs are keyed to a torque tube bolted to the wheel strut are used, which are alternated with rotating discs that rotate with/are keyed to the wheel. when the brakes are applied, a set of hydraulic pistons on the end of the brake stacks push on the entire stack assembly, which works to slow the aircraft.
what are the benefits of carbon brakes?
Carbon brakes can absorb a lot of kinetic energy and have low weight. They also have good wear and heat properties.
What is the purpose of landing gear safety pins?
a flat rubber tube installed around the brake body, when the brake is actuated, fills with hydraulic pressure from the master cylinder.as the fluid fills the tube, braking compound on the outside of the rubber tube presses against a rotating drum and slows the aircraft.
Explain the diffference between maunal, boosted, and power brakes.
manual brakes rely on the force of the pilot to apply pressure to the braking system and master cylinder.
Boosted brakes allow the pilot to input all the braking pressure required until a certain point. when the pilot continues to push,a toggle mechanism straightens out, and a valve directs hydraulic system pressure behnid the piston to assist the pilot.
power brakes only are operated by pressure from the main hydraulic system.
what is the purpose of a debooster?
deboosters reduce the pressure of the supplied hydraulic fluid to a component. this allows components that require a lower pressure to be used in a high pressure system.
how can you tell how much wear is present on a multidisc braking system?
by measuring the wear indicator pins. some pins are flush with the brake actuator housing when brake servicing is required, some require service when the wear indicator pin reaches a certain measurement.
what can cause spongy braking action?
Either air in the system OR deterioration of the flexible brake lines.
Explain the 3 common problems with braking systems and what causes them.
Overheating -- can be caused by excessive brake action instead of using the thrust reversers. excessive heat can cause heat treatment to diminish on the brake actuator housing, as well as brake disc warping.
Dragging -- happens when a brake fails to release. can cause overheating within the brake system.
Chattering or squealing -- when brakes are applied and released many times, rather than exerting a smooth and even friction between the surface of the discs. can be caused by warped or glazed discs.
list the 3 tire types and what applications they are used for.
Type III Tire — used for low pressure, GA aircraft.
Type VII Tire — Extra-high pressure tires, standard for jet aircraft
Type VIII Tire — Used for high performance jet aircraft with extremely high takeoff speeds.
List/Explain the 3 parts of a tire.
Bead — Part of the tire that provides a firm mounting surface for the tire on the wheel.
Tread — The wearing surface on the outer circumference of the tire
Sidewall — The rubber covering that extends from the tread down the the bead to protect the carcass from injury.
What is the greatest enemy of an aircraft tire?
heat
Explain the wear patterns when a tire is over/under inflated.
Underinflated — Excessive wear on the shoulders of the tire tread
Overinflated — Excessive wear on the center portion of the tire tread
What general specification is given as to what size of cut would require tire replacement?
A tire should be removed from service if the tread is cut across more than one-half of the rib width.
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