Hydraulics and landing gear
Which of the following is NOT an advantage of using hydraulic systems on an aircraft?
Greater number of mechanical components
Light weight
Ease of Installation
To what percent are hydraulic systems efficient?
80%
95%
100%
Which law states that, "pressure applied to any part of a confined liquid is transmitted with undiminished intensity to every other part?
Pascals Law
Bernoullis Principle
Newtons third law
Viscosity is defined as?
The mass by volume of a liquid
A fluids internal resistance to flow
The specific gravity of the liquid
What can happen when hydraulic fluid continuously passes through a system hot spot?
The fluid will become contaminated with abrasive particulates
The fluid may ignite and cause a failure in the system
The fluid may carbonize or sludge
What relationship exists between a liquids viscosity and its resistance to heat?
Liquids with a high viscosity have a greater resistance to heat
Liquids with a high viscosity have a reduced resistance to heat
There is no measurable relationship between heat resistance and viscosity
By comparison to the other types of hydraulic fluid discussed, how flammable is MIL-H-5606?
Least Flammable
More flammable than Mil-H-83282, but less flammable than Skydrol
Most flammable
Of what base is skydrol?
Mineral Oil
Phosphate Ester
Polyalphaolefin
How do open center hydraulic systems operate?
Positive displacement pumps and not variable displacement pumps
Idles at full pressure. The relief valve ensure pressure is constant while the users are in operation.
Fluid constantly flows, but no pressure in the system when the actuating mechanisms are idle.
In a closed hydraulic system, the selector valves are installed in?
Paralllel
Series
Either one. The orientation is unimportant
Which is true concerning aircraft that utilize non-pressurized hydraulic reservoirs?
These aircraft fly at lower altitudes and perform advanced aerobatic maneuvers
These aircraft fly at higher altitudes
These aircraft fly at lower altitudes and do not execute extreme maneuvers
Which of the following is NOT a source used to pressurize hydraulic reservoirs
Ram air
Bleed air
Hydraulic
Before servicing a hydraulic system on an aircraft, what should be ensured?
Fluid must be at ambient temperature
Must be in standard configuration
All spoilers are deployed and all flight control surfaces are moved to their max extent
A hydraulic reservoir that has been properly serviced will be?
Full
Partially Filled
Nearly Empty
Typically, micronic filters are
Paper, disposable/non-cleanable
Paper, cleanable
Metal Screen, disposable
What is the purpose of the thermal lockout device in the hydraulic filter differential pressure indicator
Prevents hydraulic fluid from flowing to the pump in the event of extreme overheat
Allows filter to be bypassed when fluid temps are low
Prevents DPI from deploying the flag when temps are low and viscosity is high
Which type of hand pump is NOT used in aviation?
Single action hand pump
Double action hand pump
Rotary hand pump
Which type of powered hydraulic pump is most commonly used in modern aircraft?
Positive displacement
Variable displacement
Vane Type
In a variable displacement hydraulic pump, during normal operation, what factor effects the output volume of the pump
Engine RPM
Pump inlet pressure
Pump outlet pressure
In a hydraulic system, where is the system fluid temperature transducer usually installed?
Reservoir
Pressure Manifold
At the outlet of the pump
A biased ply tire has its angle of the plies arranged in such a fashion that the tire becomes flexible...?
In the sidewall area of the tire
Perpendicular to the sidewall and the direction of rotation
In the bead of the tire area
The designed deflection of an aircraft tire is how many times greater that an automotive tire?
2
4
5
Which of the following is NOT a function of the grooves designed into the tread of an aircraft tire?
To absorb side loads during heavy breaking
To channel water
To assist in cooling of the tire
A tire chine is used to
Anchor the carcass plies to the bead of the tire
Protect the sidewall of the tire from damage due to operation on the unpaved landing surfaces
Deflect water away from in inlet of fuselage mounted engines
When can accurate tire pressures be checked and verified?
When on weight on wheels
Either on or off the aircraft
When the tire is unloaded
What is the cause of Chevron cuts on a tires tread?
Operation of unpaved runway. Remove from service
Operation of grooved landing surface. Acceptable as long as they do not cause chunking of the tread
Operation of a grooved landing surface and cause for tire to be deemed unserviceable
The primary purpose pf the tire bead is to
Tightly hold the tire to the wheel, ensuring an airtight fit and preventing wheel slippage
Transfer impact loads from the tread to the sidewall
Provide an anchor point for the carcass plies
Is it permissible to store aircraft tires in the horizontal orientation?
No
Yes, Indefinitely
Yes, but for no longer than 6 months
How can you determine the shelf life of an aircraft tire tube?
No mandatory shelf life
5 years
Indicated on the packaging and designated by the manufacturer
What is the purpose of tire talc?
To lubricate the tire bead to aid in the wheel mounting process
To ensure easy mounting and free movement between the tube and tire a they inflate
Its used to prevent ozone from damaging tires left in long term storage
What is the purpose of a shuttle valve
To delay the actuation of a hydraulic system from an alternate or emergency system
To isolate the normal hydraulic system from an alternate or emergency system
To transfer hydraulic fluid from one hydraulic system to another
Which of the following is NOT a function of the hydraulic accumulator
Transfer power from an adjacent system in the event of pump failure
Provide a cushioning effect for large demands placed on the pump
Provide an additional source of fluid under pressure for emergency operation
Hydraulic accumulators are typically charged with
Shop air
Oxygen
Nitrogen
What returns the piston of a single acting actuator once hydraulic pressure is removed
Hydraulic fluid, under pressure, being ported to the retract side of the actuator
A spring
A negative pressure that is created, by the hydraulic pumps, on the extend side of the actuator
Which of the following is NOT a function of a hydraulic shutoff valve?
To shut off the flow of a hydraulic fluid to and engine driven pump in the event of an engine fire
To create the hydraulic lock in a flight control actuator to provide for gust lock protection
To stop the flow of fluid to an engine driven pump in the event of a hydraulic system overheat
What component of a shutoff valve is most likely to fail?
The physical shutoff component
The electric actuating motor
Either, they are fixed together and must be replaced as one single unit
What should be done prior to disassembling a hydraulic accumulator?
Must be cycled to prevent trapped fluid
The hydraulic pump on the aircraft should be cycled to ensure the accumulator is free of air
The gas charge should be relieved from the system
In a single acting actuator, two ports exist; one supplies fluid under pressure to the fluid side of the actuator. What is the purpose of the other port.
Where hydraulic pressure is applied
To vent the spring controlled chamber of the actuator of air
As an inspection point
What type of actuator uses hydraulic fluid to power it to both the extend and retract positions?
Single acting actuator
Double acting actuator
Hydraulically balanced actuator
A rotory actuator can also be called what?
A rack and pinion actuator
A hydraulic motor
A non-linear actuator
Of the following, which aircraft systems are not operated by a high pressure pneumatic system?
Wheel brakes
Flap actuation systems
Thrust reversers
High pressure pneumatic systems operate at pressures ranging from
500-1000 psi
1000-3000 psi
3000-5000 psi
What is the main disadvantage to pneumatic systems that use a high pressure bottle?
The high heat generated by the system
As an incompressible fluid, the gas in the system imparts too much mechanical shock upon the system and its compnents
Operation is limited by the small supply of bottled air
What is the purpose of a restrictor installed in a high pressure pneumatic system
To reduce the pressure downstream of the restrictor
To reduce the speed of actuation of the pneumatic components, downstream of the restrictor
The limit the flow of fluid in only one of two directions
In a pneumatic system, where is the moisture separator always installed?
Downstream of the compressor
Upstream of the compressor
Between the storage bottle and the compressor
How can you know that a chemical drier is serviceable?
When serviceable the cartridge should be blue in color
When serviceable the cartridge should be red in color
When serviceable the cartridge should be green in color
At what pressures do medium pressure pneumatic systems operate?
1000-3000 psi
500-1000 psi
50-150 psi
What is the most common source of pneumatic power for a medium pressure system?
Vane type compressor pump
A pressurized storage bottle
The engine bleed air system
Which of the following systems are operated by a medium pressure pneumatic system?
Wheel brakes
Engine starting
Opening and closing doors
Which of the following systems are operated by a low pressure pneumatic system?
Air conditioning and pressurization
Instruments
Wing and cowl anti-icing
For what reason are a single piece aircraft wheels NO LONGER used on modern aircraft?
Do not provide an adequate structure to contain the high pressures of modern aircraft tires
The strength and robustness of modern aircraft tires makes it impossible to install them on to single piece wheels.
Single piece wheels are unable to sufficiently disburse heat during heavy breaking.
What is the purpose of a thermal plug on aircraft wheels?
To prevent the wheel and tire from bursting due to excessively high temperatures
To prevent an assembly from damage due to erroneous over-inflation
To fuse minor air leaks in the wheel
What is the purpose of the over-inflation safety plug
To prevent the wheel and tire from bursting due to excessively high temps
To prevent an assembly from damage due to erroneous over-inflation
To fuse minor leaks in the wheel
Other than protecting the bearing cavity from FOD, what additional purpose may a hub cap be designed to facilitate?
Hydraulic fluid, under pressure, being ported to the retract side of the actuator
It provides a redundant means to hold the wheel onto the axle in the event that the axle nut becomes unserviceable
The hub cap engages the wheel speed transducer to provide electronic wheel speed data
What is the effect upon a component that experiences galling?
Metal welds and surface metal is destroyed as the motion continues and pulls the metal apart in the direction of motion
Tiny particles contaminate the bearing surface and produce a less than smooth surface
Corrosion occurs as a result of water penetrating the protective coating of the metal part
What is the best method for inspecting for cracks in aluminum aircraft wheels?
Die penetrant inspection
Visual Inspecion
Eddy current inspection
In a single disk brake system, from where does the energy to apply the brakes come?
From the aircraft hydraulic system, regulated by the input from the pilot's rudder pedals
From the pilot and combined with hydraulic pressure from the aircraft hydraulic system
From the pilot, transitted through a closed hydraulic system
What is the purpose of the keyways in the rotor disks if a multiple disk brake?
To engage and be rotated by the wheel
To provide a mounting point for the brake caliper
To allow the alignment of the brake caliper and rotor disks
What is the benefit of using segmented disk brakes in a multi-disk break vs standard disks?
Superior cooling characteristics
Increased strength and cooling characteristics
Segmented rotors provide ease in maintenance because they can be installed without removing the aircraft wheel tire assembly
In a floating disk brake, what component adjusts for brake lining wear during operation?
The return spring
The adjusting pin grip
The pressure plate lining puck
An independent brake system differs from the other types because?
It is the only system that does not utilize hydraulic fluid under pressure from the aircraft hydraulic system
It is the only system that uses hydraulic fluid under pressure from the aircraft hydraulic system
It is the only system that uses no hydraulics to operate; only pilot strength through push pull rods
If an airplane has no nosewheel steering system, what allows the aircraft to maneuver on the ground?
The aircraft turns by taxiing at a rapid pace and using the rudder to cause angular deflection
These aircraft utilize rigid landing gear systems and must be towed to and from the runway
Differential braking
What is the purpose of the compensating port in a master cylinder actuator?
It allows the fluid to expand safely without causing extension of the actuator
It account for operation during cold temperatures when the fluid is highly viscous
It provides a return path for the anti-skid system
In a boosted brake system, when does the airframe hydraulic system pressure act upon the brake units?
Any time the pilot presses the brake pedals. The brakes are entirely operated by the airframe hydraulic system which is only regulated by the varying application of the brake pedals, by the pilot.
Only during heavy braking
A boosted brake system does not use airframe hydraulic system pressure to operate
In power brake system, what regulates the fluid pressure sent to the brake units (excluding ant-skid operations)?
Actuation of the brake master cylinder, based on pilot input
The brake control valve in response to pilot input on the rudder pedals
Corrosion occurs as a result of water penetrating the protective coating of the metal part
In power brake systems what provisions help to supply the pilots with the control sensations lost through the use of power brake systems
Artificial feel systems
Visual braking indicators on the instrument panel
Adjustable friction locks on the rudder pedals
What is the purpose of the brake accumulator?
To dampen pressure surges from the hydraulic system while brakig
To ensure the bootstrap circuit will remain pressuerized in the event that both the hydraulic system pumps fail
To prvide enough hydraulic fluid, under pressure, to operate the brakes a set number of times, in the case of an emergency
What are the three components of the anti-skid system
Brake control valve, anti-skid control unit, and anti-skid control valves.
Wheel speed transducer, anti-skid contrl unit, and anti-skid control valves
Wheel speed transducer, anti-skid control unit, and brake accumulator
How are anti-skid control valves controlled
Electrically
Mechanically
Hydraulically
When inspecting brake wear pin indicators for brake lining serviceability, should the brakes be applied or released?
Released
Applied
Either
Which of the following is not a factor in the number of wheels and tires designed on an aircraft?
The max number of passengers the aircraft is designed to carry
The type of surface the aircraft is designed to land upon
The gross weight of the aircraft
What term is used to describe the drag associated with the extended landing gear, protruding into the slipstream?
External fairing drag
Component aero drag
Parasite drag
Which of the following is not one of the two ways the landing gear control the landing impact energy?
The shock is absorbed by converting the energy into heat energy
The shock energy is altered and transferred throughout the airframe at a different rate
The shock is absorbed by the pneumatic tires and refocused and transferred back to the landing surface
Identify the two types of shock absorbing landing gear used on aircraft?
Shock strut type and pneumatic tube type
Flexible leaf type and schock strut type
Flexible leaf type and hydraulic tube type
To which category do the landing skids of a helicopter belong?
Rigid gear
Leaf-type
Bungee type
In an air/oil shock strut, which camber contains the air or nitrogen charge?
Upper chamber
Lower chamber
Air charge moves between upper and lower chamber.
In an air/oil shock strut, upon landing, does the fluid flow past the metering pin increase or decrease as the strut further collapses?
Increases
Decreases
The flow is metered and regulated to remain constant
What compels the strut to extend after the initial impact, and corresponding collapse, of landing?
A large return spring integral to the shock absorber assembly
The gas charge in the upper cylinder that has become compress by the collapsing of the strut
The metering pin forces fluid to flow to the lower chamber, causing the strut to extend to the normal extension
What is the purpose of the nosewheel centering cams installed in the NLG shock strut?
To mechanically straighten the nosewheel when the shock strut is fully extended
To mechanically return the nosewheel to the centered position after a nosewheel steering command is removed
To provide alignment indication for reconnecting the torque links
In a MS28889 strut servicing valve, what must the technician do to bleed the gas charge from the strut during servicing
The technician must remove the valve core from the servicing valve
The technician must depress the valve core plunger
The technician must rotate the swivel nut sufficiently to allow the air to escape.
Which of the following describes the condition/alignment that would cause an aircrafts wheels to show a tendency to track toward the center of the fuselage as the aircraft moves forward?
Toe in
Toe out
Positive camber
Which of the following describes the condition/alignment whereby the tops of the wheels, when mounted on the aircraft, lean in to the fuselage?
Toe out
Negative camber
Positive camber
What is the name of the component, in retractable type landing gear systems, that is located on the top of the upper shock strut cylinder and attaches the strut to the airframe structures?
Torque mount
Trunnion
Integral landing gear mount
What is the purpose of the drag brace in a retractable type landing gear system?
It is used to restrain against the pivot action built into the trunnion attachment
It is used to prevent landing gear shimmy when in transit on the ground
It is used to ensure that the nosewheel is straight before retracting it into the wheel well
What device is used in landing gear systems that provides position indications without mechanical contact?
Microswitch
Transformer switch
Proximity sensor
What of the following is NOT a purpose of the NLG torque links?
Provides an attachment point for the tow bar
It prevents the shock strut from overextending during takeoff
It transfers the rotational input from the nosewheel steering NWS system to the nosewheel
What is the most common type of nosewheel steering system in small aircraft?
Electric
Mechanical
Electro-Hydraulic
Landing gear shimmy is described as
The tendency to oscillate rapidly, or shimmy, while extending and/or retracting the gear
The tendency to oscillate rapidly, or shimmy, under braking
The tendency to oscillate rapidly, or shimmy, at certain speeds
In a NWS system on a large transport category aircraft, from what two sources can the steering system receive input?
The yoke and rudder pedals
The steering tiller and rudder pedals
The steering tiller and yoke
If the NWS system fails, the system is said to revert to
Free-castering mode
Hydraulic lock mode
Standby mode
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