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AVMT 2206 Final
| Question | Answer |
|---|---|
| To prevent external and internal leakage in aircraft hydraulic units, the most commonly used type of seal is the | O-ring seal |
| Which allows free fluid flow in one direction and no fluid flow in the other direction? | Check valve |
| Select the valve used in a hydraulic system that directs pressurized fluid to one end of an actuating cylinder and simultaneously directs return fluid to the reservoir from the other end. | Selector |
| (1) Relief valves are used in pneumatic systems as damage-preventing units. (2) Check valves are used in both hydraulic and pneumatic systems. Regarding the above statements, | both No. 1 and No. 2 are true |
| One of the distinguishing characteristics of an open-center selector valve used in a hydraulic system is that | fluid flows through the valve in the OFF position |
| What type of packings should be used in hydraulic components to be installed in a system containing Skydrol? | Packing materials made for ester base fluids |
| Relief valves are used in pneumatic systems | as damage-preventing units |
| The removal of air from an aircraft hydraulic system is generally accomplished | by operating the various hydraulic components through several cycles |
| The component in the hydraulic system that is used to direct the flow of fluid is the | selector valve |
| The purpose of the pressure regulator in a hydraulic system is to | maintain system operating pressure within a predetermined range and to unload the pump |
| A flexible sealing element subject to motion is a | packing |
| Which characteristics apply to aircraft hydraulic systems? 1. Minimum maintenance requirements. 2. Lightweight. 3. About 80 percent operating efficiency (20 percent loss due to fluid friction). 4. Simple to inspect. | 1, 2, 4 |
| Extrusion of an O-ring seal is prevented in a high-pressure system by the use of a | backup ring on the side of the O-ring away from the pressure |
| What is one advantage of piston-type hydraulic motors over electric motors? | There is no fire hazard if the motor is stalled |
| Generally, the first step in removing an accumulator from an aircraft is to | relieve system pressure |
| If a hydraulic brake system uses neoprene rubber packing materials, the correct hydraulic fluid to service the system is | mineral base oil |
| The internal resistance of a fluid which tends to prevent it from flowing is called | viscosity |
| Which is a characteristic of petroleum base hydraulic fluid? | Flammable under normal conditions |
| (1) When servicing aircraft hydraulic systems, use the type fluid specified in the aircraft manufacturer's maintenance manual or on the instruction plate affixed to the reservoir or unit. (2) Hydraulic fluids for aircraft are dyed a specific color | both No. 1 and No. 2 are true |
| Petroleum base hydraulic fluid is which color? | Red |
| Which of the following is adversely affected by atmospheric humidity if left unprotected? 1. MIL-H-5606 hydraulic fluid. 2. Skydrol hydraulic fluid. 3. None of the above. | 2 |
| Which is a characteristic of synthetic base hydraulic fluid? | High flash point |
| Which statement about fluids is correct? | All fluids readily transmit pressure |
| Two types of hydraulic fluids currently being used in civil aircraft are | mineral base, and phosphate ester base |
| Which of the following lists only desirable properties of a good hydraulic fluid that has chemical stability? | Low viscosity, high flash point, high fire point |
| Characteristics of MIL-H-8446 (Skydrol 500 A & B) hydraulic fluid are | light purple color, phosphate ester base, fire resistant, butyl rubber seals |
| Where can information be obtained about the compatibility of fire-resistant hydraulic fluid with aircraft materials? | Fluid manufacturer's technical bulletins |
| Characteristics of MIL-H-5606 hydraulic fluid are | red color, petroleum base, will burn, uses synthetic rubber seals |
| If an aircraft hydraulic system requires mineral base hydraulic fluid, but phosphate ester base hydraulic fluid is used, what will be the effect on the system? | System will be contaminated, fluids will not blend, and the seals will fail |
| How can the proper hydraulic fluid to be used in an airplane be determined? | Consult the aircraft manufacturer's service manual |
| The primary purpose of a hydraulic actuating unit is to transform | fluid pressure into useful work |
| The primary function of the flap overload valve is to | prevent the flaps from being lowered at airspeeds which would impose excessive structural loads |
| A unit which transforms hydraulic pressure into linear motion is called | an actuating cylinder |
| Unloading valves are used with many engine-driven hydraulic pumps to | relieve the pump pressure |
| What safety device is usually located between the driving unit and hydraulic pump drive shaft? | Pump drive coupling shear section |
| Excluding lines, which components are required to make up a simple hydraulic system? | Pump, reservoir, selector valve, and actuator |
| In a gear-type hydraulic pump, a mechanical safety device incorporated to protect the pump from overload is the | shear pin |
| Pressure is a term used to indicate the force per unit area. Pressure is usually expressed in | pounds per square inch |
| If two actuating cylinders which have the same cross-sectional area but different lengths of stroke are connected to the same source of hydraulic pressure, they will exert | equal amounts of force and will move at the same rate of speed |
| 100 PSI has been built up in a hydraulic system. The hand pump piston is 1 inch in diameter. A 1/2-inch line connects the hand pump to an actuating cylinder 2 inches in diameter. What is the pressure in the line between the hand pump and the actuator? | 100 PSI |
| Heat exchanger cooling units are required in some aircraft hydraulic systems because of | high pressures and high rates of fluid flow |
| The unit which causes one hydraulic operation to follow another in a definite order is called a | sequence valve |
| The purpose of a hydraulic pressure regulator is to | relieve the pump of its load when no actuating units are being operated |
| What type of valve in an aircraft hydraulic system permits fluid to flow freely in one direction, but restricts the rate at which fluid is allowed to flow in the other direction? | Orifice check valve |
| A hydraulic accumulator is charged with an air preload of 1,000 PSI. When a hydraulic system pressure of 3,000 PSI is developed, the pressure on the air side of the accumulator will be | 3,000 PSI |
| How is the air in a hydraulic accumulator prevented from entering the fluid system? | By physically separating the air chamber from the oil chamber with a flexible or movable separator |
| After a hydraulic accumulator has been installed and air chamber charged, the main system hydraulic pressure gauge will not show a hydraulic pressure reading until | the fluid side of the accumulator has been charged |
| Some hydraulic systems incorporate a device which is designed to remain open to allow a normal fluid flow in the line, but closed if the fluid flow increases above an established rate. This device is generally referred to as a | hydraulic fuse |
| When hydraulic system pressure control and relief units fail to function properly, how are most systems protected against overpressure? | A shear section on the main hydraulic pump drive shaft |
| Before removing the filler cap of a pressurized hydraulic reservoir, in order to service the system, you must | relieve the air pressure |
| Hydraulic system accumulators serve which of the following functions?1. Dampen pressure surges.2. Supplement the system pump when demand is beyond the pump's capacity.3. Store power for limited operation of components if the pump is not operating. | 1, 2, 3 |
| Chattering of the hydraulic pump during operation is an indication | that air is entering the pump |
| Quick-disconnect couplings in hydraulic systems provide a means of | quickly connecting and disconnecting hydraulic lines without loss of fluid or entrance of air into the system |
| Which seal/material is used with phosphate ester base hydraulic fluids? | Butyl rubber |
| A hydraulic pump is a constant-displacement type if it | delivers a uniform rate of fluid flow |
| A hydraulic motor converts fluid pressure to | rotary motion |
| Hydraulic fluid filtering elements constructed of porous paper are normally | discarded at regular intervals and replaced with new filtering elements |
| In a hydraulic system that has a reservoir pressurized with turbine-engine compressor bleed air, which unit reduces the air pressure between the engine and reservoir? | Air pressure regulator |
| What is the main purpose of a pressurized reservoir in a hydraulic system? | Prevent hydraulic fluid from foaming |
| One of the main advantages of skydrol is its | wide operating temperature |
| To check the air charge in a hydraulic accumulator, | reduce all hydraulic pressure, then observe the reading on the accumulator air gauge |
| Chatter in a hydraulic system is caused by | air in the system |
| If hydraulic fluid is released when the air valve core of the accumulator is depressed, it is evidence of | a ruptured diaphragm or leaking seals |
| The purpose of restrictors in hydraulic systems is to | control the rate of movement of hydraulically operated mechanisms |
| Seals used with a mineral base hydraulic fluid are identified by which color code? | Blue dot or stripe |
| Exposure to and/or storage near which of the following is considered harmful to aircraft tires? 1. Low humidity. 2. Fuel. 3. Oil. 4. Ozone. 5. Helium. 6. Electrical equipment. 7. Hydraulic fluid. 8. Solvents. | 2, 3, 4, 6, 7, 8 |
| What would be the effect if the piston return spring broke in a brake master cylinder? | The brakes would drag |
| In brake service work, the term 'bleeding brakes' is the process of | withdrawing fluid from the system for the purpose of removing air that has entered the system |
| A pilot reports the right brake on an aircraft is spongy when the brake pedal is depressed in a normal manner. The probable cause is | air in the brake hydraulic system |
| Aside from an external leak in the line, what will cause parking brakes to continually bleed off pressure? | An internal leak in the master cylinder |
| Why do most aircraft tire manufacturers recommend that the tubes in newly installed tires be first inflated, fully deflated, and then reinflated to the correct pressure? | To allow the tube to position itself correctly inside the tire |
| After performing maintenance on an aircraft's landing gear system which may have affected the system's operation, it is usually necessary to | make an operational check with the aircraft on jacks |
| Why do tire and wheel manufacturers often recommend that the tires on split rim wheels be deflated before removing the wheel from the axle? | As a safety precaution in case the bolts that hold the wheel halves together have been damaged or weakened |
| If it is determined that spongy brake action is not caused by air in the brake system, what is the next most likely cause? | Deteriorated flexible hoses |
| A stripe or mark applied to a wheel rim and extending onto the sidewall of a tube-type tire is a | slippage mark |
| When bleeding aircraft brakes, one of the indications that the air has been purged from the system is | firm brake pedals |
| Overinflated aircraft tires may cause damage to the | wheel flange |
| On all aircraft equipped with retractable landing gear, some means must be provided to | extend the landing gear if the normal operating mechanism fails |
| What is the purpose of the torque links attached to the cylinder and piston of a landing gear oleo strut? | Maintain correct wheel alignment |
| The removal, installation, and repair of landing gear tires by the holder of a private pilot certificate on an aircraft owned or operated is considered to be | preventive maintenance |
| Internal leakage in a brake master cylinder unit can cause | the pedal to slowly creep down while pedal pressure is applied |
| The purpose of a sequence valve in a hydraulic retractable landing gear system is to | ensure operation of the landing gear and gear doors in the proper order |
| What type of valve is used in the brake actuating line to isolate the emergency brake system from the normal power brake control valve system? | A shuttle valve |
| When servicing an air/oil shock strut with MIL-5606 the strut should be | collapsed and fluid added at the filler opening |
| Instructions concerning the type of fluid and amount of air pressure to be put in a shock strut are found | in the aircraft manufacturer's service manual |
| Aircraft tire pressure should be checked | at least once a week or more often |
| If an aircraft shock strut (air/oil type) bottoms upon initial landing contact, but functions correctly during taxi, the most probable cause is | low fluid |
| Extension of an oleo shock strut is measured to determine the | proper operating position of the strut |
| If a shock strut bottoms after it has been properly serviced, the | strut should be removed, disassembled, and inspected |
| The correct inflation pressure for an aircraft tire can be obtained from | the aircraft service manual |
| What should be checked when a shock strut bottoms during a landing? | Fluid level |
| How can it be determined that all air has been purged from a master cylinder brake system? | By noting whether the brake is firm or spongy |
| The fusible plugs installed in some aircraft wheels will | melt at a specified elevated temperature |
| What action, if any, should be taken when there is a difference of more than 5 pounds of air pressure in tires mounted as duals? | Correct the discrepancy and enter in the aircraft records |
| How long should you wait after a flight before checking tire pressure? | At least 2 hours (3 hours in hot weather) |
| When an empty shock strut is filled with fluid, care should be taken to extend and compress the strut completely at least two times to | ensure proper packing ring seating and removal of air bubbles |
| On most aircraft, the oil level of an air and oil shock strut is checked by | releasing the air and seeing that the oil is to the level of the filler plug |
| A landing gear position and warning system will provide a warning in the cockpit when the throttle is | retarded and gear is not down and locked |
| What device in a hydraulic system with a constant-delivery pump allows circulation of the fluid when no demands are on the system? | Pressure regulator |
| A fully-charged hydraulic accumulator provides | a source for additional hydraulic power when heavy demands are placed on the system |
Created by:
jsatterfield9