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2a353 Volume 3 CH 1

USAF Tactical Aircraft Maintenance CDC Questions 2016

QuestionAnswer
How is Oxygen separated from other gases in the air? By compressing and cooling the air
Why must aviators breathing oxygen be "bone dry"? To ensure operation of oxygen system components. Oxygen with a high moisture content would freeze at high altitudes, causing the oxygen system to be inoperative.
List some of the warning signs of hypoxia Blurred vision, slight shortness of breath, a vague week feeling, light dizziness
What is the maximum pressure at which low pressure gaseous oxygen cylinders are charged? 450 psi m
What color are low pressure gaseous oxygen cylinders painted? yellow
How are oxygen tubes color-coded? With bands of green and white cellulose tape
What two types of connections are used in low pressure oxygen systems? pipe-thread and flared tube connections
What component reduces system pressure in a high pressure gaseous oxygen system? a pressure reducer valve
What construction methods prevent high pressure gaseous oxygen cylinders from shattering? heat treated alloy wrapped with steel wire
What are the two main types of oxygen regulators? the continuous flow and pressure demand type
Whats a disadvantage of the continuous flow regulator as compared to other types? wastes oxygen
The MD-1 oxygen regulator can be used with what types of oxygen systems? with high or low pressure gaseous or LOX systems
In an emergency the pressure demand regulator can supply oxygen to what altitude? 50,000 feet
What should system pressure be during an operational check of a regulator? near normal operating pressure
Explain hoe the molecular sieve bed operates Nitrogen in the air is absorbed in one bed of molecular sieve while oxygen passes through the bed. When the molecular sieve becomes saturated, the concentrator vents the nitrogen overboard
What happens if the MSOGS concentrator fails? It will turn on an oxygen caution light in the cockpit and automatically switch to the backup oxygen supply
Whats the temperature of liquid oxygen? -297 degrees F
Why should liquid oxygen never be sealed, capped, or trapped in a container without a relief valve? It will rupture the container
What factors are used to determine convertor size? The number of crew, mission duration, and the type of oxygen regulation equipment used
Whats the probable cause if frost appears on the outside of a LOX container? Vacuum loss
How are pressure control valves controlled? Spring-loaded bellows
Whats the primary purpose of the pressure closing valve? To maintain a constant head pressure on top of the liquid oxygen in the storage container
Whats the normal position of the pressure opening valve? Closed
Why is it important to ensure there is no moisture in the fill, buildup, and vent valve? It may freeze in the vent position
In what position should you manually place the buildup/vent valve during a filling operation? VENT position
How are the check valves in quick disconnects operated? Automatically
What are the two modes of operation in the supply sequence of the liquid oxygen system? The economy mode and demand mode
What Technical Order covers the requirements for LOX systems inspection? -6 technical manual for the specific aircraft
What is the purpose of a bleed air system? To operate or control pneumatic systems or components
What are three sources of bleed air used for system operations on jet aircraft? Aircraft engines; ground air cart; and gas turbine compressors, gas turbine units, to Auxillary power units
What equipment provides bleed air when the aircraft is on the ground with the engine shutdown? A ground air cart
List the components of a bleed air system Check valves, shutoff valve, wing isolation or body crossover valves, flow control valves, pressure regulating valves, bleed air ducting, and the necessary controls
What is the purpose of a ground-air-connection check valve? Prevent the escape of bleed air from the system
What material is usually used for high pressure/high temperature ducting? Stainless Steel
What action should you take to ensure a good airtight seal when installing a V-Band clamp? Tap around the circumference of the clamp as its tightened
Why should you install the bottom bolts on a bolted flange duct first? This forms a cradle and holds the gasket in place while you install the remaining bolts
Besides stainless steel, what other materials can be used in the construction of medium-pressure/medium-temperature ducting? Titanium to aluminum alloy
What type of lubricant can be used on beaded duct sleeves to aid in installation? Water only
Where in the Aircraft is molded fiberglass ducting used for distributing conditioned air? Cabin Area
Whats the purpose of gaskets? To make an airtight seal with most types of flange connections
What devices are installed in bleed air systems to compensate for thermal expansion of ducting? Expansion joints(bellows), thermal compensators, universal joints, loops, horseshoe bends, and offsets
Whats the most important reason for insulating ducts? To prevent heat damage to structural members, electrical wiring, and combustible material, as well as hydraulic, oxygen, and fuel lines
What type of insulating material is fireproof? Fiberglass fabric blankets
What is the purpose of the rubber accordion boot wrapped around the duct between the sections of the insulation? This boot allows for differences in expansion rates of the duct and insulation
Whats used to lace the studs together in a metal foil blanket? Wire
What are the most common types of duct damage? Scratch, minor dent, major dent,and gouge
Define gouge A defect wherein the surface of the material is cut or removed sufficiently to cause the duct wall thickness to be reduced
Which bleed air duct system is subjected to the highest pressure/temperature? High pressure/high temperature
What should you do anytime you locate a non permissible leak in the high-pressure/high temperature section of the bleed air system? Inspect the aircraft structure in the immediate area of the leak for heat danage
What is air conditioning? The simultaneous control of temperature, humidity, and air distribution within a space
Does heat always move to cold or does cold always move to heat? Heat always moves to cold
While the aircraft is in flight, what controls the flow of ram air to the PHE? Moveable ram air inlet and/or exit doors that modulate in flight
During low airspeeds or ground operation what induces cooling airflow to the PHE when there is not enough ram air to cool the PHE? Ejectors
What consists of a centrifugal air compressor and an expansion turbine, and is often known as the pack? Air cycle machine (ACM)
Why would some of the outlet air from the PHE need to bypass the air cycle machine? If cabin temperature controls call for warmer air
What component provides an additional stage of cooling after the bleed air has left the PHE and, if required, the air cycle machine? Secondary Heat Exchanger
What is the primary purpose of the refrigeration bypass valve? To prevent water from freezing in the water separator
What component uses centrifugal force to remove moisture in the air that is caused by rapid cooling? The water separator
What two forms of energy are essentially interchangeable? Pressure and temperature
What happens to heat the engines bleed air as it passes through the PHE? Some of the heat is transferred to ram air
What happens to the pressure of the engine bleed air as it passes through the PHE? Almost no change
What happens to the air as it enters the compressor of the air cycle machine? The pressure increases and, therefore, the temperature increases
What results in a very large decrease to the air cycle machine? As the air expands across the turbine, the pressure decreases greatly. The pressure decrease, coupled with the energy extracted to drive the compressor, results in a very large decrease in temperature.
What are the two methods of cooling used in typical bootstrap system? 1). By transferring heat to the ram air, or 2). removing most of the heat by expanding it and converting it into work to drive the compressor
The refrigeration bypass valve opens so that warm air can mix with the air in the water separator if the water separators outlet air temperature falls below what temperature? 38 degrees F
Explain the difference between preconditioned air and conditioned air Once the air has cycled through the entire system with the exception of the water separator, it is called preconditioned air. Preconditioned bleed air becomes conditioned air when it has made its way through the water separator
What percentage of the earths air is nitrogen? 78%
List the three pressurization ranges Unpressurized range, isobaric range, and differential range
What is isobaric range? 8,000 to 21,000 feet above sea level
Where does the differential range extend? From where the isobaric range stops to the maximum altitude of the aircraft
What component opens and closes to control the amount of air leaving the aircrafts pressurized area? Outflow valve
What is the approximate atmospheric pressure at sea level? 14.7 psi
The aneroid is fully expanded and the metering valve is closed at what specific altitude? 8,000 feet
What two pressures are applied to the differential diaphragm? Control and atmospheric pressure
What section of the pressure regulator protects the crew from too fast a rise in cabin pressure? The rate control section
In addition to a regulator, two outflow valves, and a pneumatic relay, what other component is a part of the dual-differential regulator? Dump Valve
What component operates as a safety valve if the regulator fails? Outflow valve
Why are two outflow valves used on aircraft with large crew areas? Because of the large volume of air to be relieved
How can the dump valve be operated in case of electrical failure? Manually
What are the three features of the pressure controller? Isobaric, firrential, and rate controls
How is isobaric control maintained? Adjusting spring tension
What types of pressure act on the differential controllers diaphragm? Control head and atmospheric
How is the rate control orifice size adjusted? Rate control knob
During a dive, what prevents damage cause by reverse flow of atmospheric air? The ball check valve
Describe the purpose of the manual control valve? It is used to manually set and regulate the control pressure if the automatic cabin pressure pressure controller fails
What happens if the pressure regulator test handle remains in the TEST position? The aircraft will pressurize on the ground
Where are the fire detectors normally placed on aircraft? On conventional aircraft they are placed in the engine and baggage compartments. On jet aircraft they are placed on the engine section, nacelle, or tail cone
How are the thermal switches connected? In parallel with each other, and in series with the warning light
What re the two types of thermos witches? FENWAL switch and Iron Fireman switch
How do the FENWAL and Iron Fireman detector switches operate? The inside of the switch has a low coefficient of expansion, while the shell has a high coefficient of expansion. When they are heated, they will expand and contact will be made.
What causes a thermocouple fire detector system to activate? A rapid rate of temperature increase beyond normal engine warm-up
What are the three circuits in the thermocouple fire warning system? The detector, alarm, and test circuit
How are the thermocouples connected inn respect to each other? In series
What does a photoelectric detector cell consist of? A glass envelope, which is coated on the inside with infrared-sensitive lead sulfide
The amplifier of a photoelectric fire detection system is sensitive to what frequencies? Between 7 and 60 hz
How can you distinguish the fire warning light from the overheat light in the photoelectric fire detection system? The overheat light flashes and the fire warning is steady
What are fire detector sensing loops made of? A center conductor embedded in a semiconducting compound enclosed within a tube
How do liquid agents extinguish fire? By excluding oxygen from the fire area
How will an insufficient nitrogen charge effect agent discharge? The cylinder won't have enough pressure to discharge properly
What shape are aircraft fire extinguisher containers? Spherical
What prevents leakage between the bonnet assembly and container during discharge? A rubber O-ring packing
How are squibs fired? Applying 28 VDC to the squib
What is incorporated in some two-shot systems to delay electrical current to the bonnet assemblies? Time delay relay
What does a flashing re light in a fire emergency control handle indicate? An overheat
What steps should be taken to remove liquid fire extinguishing agents if moisture or high temperature was present? 1).Purge the area and surface with clean, dry air 2). Clean the affected areas with cleaning solution and rinse with water 3). Drain excess water and dry the area with cloths, or air pressure no greater than 10 psi
Created by: wcarrel11