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2a353 Volume 3 CH 3

USAF Tactical Aircraft Maintenance CDC Questions 2016

QuestionAnswer
When the opening of a filled balloon is closed, why is there no action on the balloon? Because the pressure of the gas inside the balloon is exerted equally in all directions
What type of energy does a falling object possess? Kinetic energy
Can energy pass from potential to kinetic and back to potential? YES
What is Newton's 1st Law of Motion? A body at rest remains at rest and a body in motion continues to move at a constant speed in a straight line, unless acted upon by an external force
What is Newton's 2nd Law of Motion? An unbalanced force on a body produces, or tends to produce, an acceleration in the direction of the force, and that acceleration is directly proportional to the force and inversely proportional to the mass of the body
Which law of physics best explains how a jet engine produces forward thrust? Newton's 3rd Law of Motion
State Bernoulli's principle When the speed of a stream of gas increases, the pressure of the gas decreases, and when the speed of the gas decreases, the pressure increases.
When a jet engine reaches idle, what determines how the fuel control regulates engine speed? Power Level Setting
What two forms of energy does a jet engine produce? Thrust and heat
Approximately what percent of the energy produced by the fuel is needed to maintain the jet engine operating cycle? 60%
Where is the point of highest pressure within a jet engine? In the diffuser section
On a jet engine that does not have an afterburner, where is the point of highest temperature? In the combustion section
Where is the point of highest airflow velocity in a jet engine? At the ejector nozzle
What is the purpose of the turbine stator? To increase the velocity of the gases striking the turbine blades
After the gases leave the turbine section and enter the exhaust section, what type of velocity do they have? Axial
What straightens the flow path of gases in the exhaust cue? The vanes in the exhaust case
In a multistage turbine, what is the arrangement of the shafts? One shaft is hollow, allowing the other shaft to operate inside it
Which turbine drives the front compressor on a dual spool engine? The rear turbine
What is a turbojet engine? An air-dependent, thermal, jet propulsion device
Name the three main sections of a gas turbine engine Compressor, combustion chamber, and turbine
What are the 2 types of compressors used in jet engines? Centrifugal and axial flow
How do pressure pulsations in a centrifugal compressor present themselves? As shock waves or irregular movement of air through the compressor
What effect do pressure pulsations have on a compressor? Rapidly reduced efficiency
Why is it not desirable to use multi-stage centrifugal compressors to increase the pressure ratio? Because of the complicated construction and increased weight of the engine that would result
What two needs stimulated the development of the axial flow compressors? More power and a more economical engine
How does the air pass through an axial flow compressor? The air travels rearward along the xis of the engine, and the air pressure is increased at each stage of compression
How are axial flow compressor rotor blades similar to an aircraft propellor? They both are airfoil shaped and move an air mass
What is the purpose of the stationary vanes that are located behind each rotor wheel in the single-spool axial flow compressor? They direct the air onto the blades of the succeeding rotor wheel and also cause the air pressure to increase
How are the compressor rotor blades and stator vanes arranged in a multiple-stage, axial flow compressor? The rotor blades are graduated from long to short through the stages of compression. The stator vanes are also granted in size to correspond in length with the rotor blades.
Identify 2 reasons the dual spool axial flow compressor was designed Ease of starting and reduction compressor stalls
What unit determines the speed of the N2 (high pressure) rotor in a dual spool compressor? The fuel control
Which type of compressor is more durable, the axial flow or the centrifugal? Centrifugal
Why is getting good combustion in a gas turbine engine so complex? Because the fuel and air must combine rapidly, the combustion process must not use excessive energy and space, and the combustion chamber must not overheat
What is combustion efficiency? A measure of the ability of the combustion chamber to burn the fuel completely and to mix the elements throughly with the remainder of the air charge before the gases reach the turbine nozzle
How is combustion efficiency computed? By comparing the heat energy received by the air as it passes through a test combustion chamber with the known energy that was added to the chamber in the form of fuel
What are two by products of combustion? Carbon deposits and carbon monoxide
What are the 2 purposes of the combustion section? To burn the fuel and to deliver the resulting gas to the turbine at a temperature that does not exceed a predetermined limit for the particular engine in use
What is the approximate air to fuel ratio used for the actual burning process in a combustion chamber? 15:1
Name the 3 types of combustion chambers Can, annular and can-annular
What supports the annular type combustion chamber in the front and the rear? The front of the chamber is attached to the burner support, and the rear of the chamber is supported on the outside by the stator blade support ring of the first-stage turbine and on the inside by the stator inlet ring of the first stage turbine
How does the additional air that is required to support combustion and cool the annular combustion chamber reach the chamber walls? Through elongated slots and round holes in the sections of the chamber walls
What supports the can-annular combustion chambers within the combustion section on certain engines? Fuel nozzles in the front and turbine nozzle case at the rear
What is the purpose of a fuel nozzle? To introduce fuel into the combustion chamber
Multiple fuel nozzles are used for what 2 purposes? To handle large quantities of fuel with even distribution and to minimize the variation that might be caused by a clogging of any one of the nozzles
In a dual-orifice type of fuel nozzle, fuel is injected into the engine combustion chamber from which orifices for high engine thrust operation? Both the Primary and secondary orifices
Name the 3 types of turbines Impulse, reaction, and reaction impulse
What type of turbine design is used on most jet engines? Reaction impulse
What is inserted between the rotating blades on multi stage turbines? Stationary turbine nozzle vanes
What characteristics and values must be considered when designing turbines? Exhaust gas flow rate, shaft RPM, turbine inlet and outlet temperature and pressures, turbine exhaust velocity, and the required power output
What is the most frequently used method of attaching the turbine blades to the rotor disc? The Fir tree method
Describe the Fir tree attachment A series of grooves and notches broached in the rim of the turbine rotor disc
What 3 types of fasteners are used to secure the turbine blades to the rotor discs? Steel pins, lock strips, and rivets
What are the two principal turbine blade configurations? Shrouded and un-shrouded
What 3 things does the shroud on shrouded turbine blades do? Reduce blade vibration, improve airflow, and increase engine efficiency
The term exhaust duct refers to what? The engine exhaust pipe connecting the turbine outlet and the jet nozzle of a non-augmenter engine
What are the 2 purposes of the engine exhaust duct? To collect and straighten the gas flow that comes from the turbine and to increase the velocity of the gases before they are discharged from the exhaust nozzle
What may occur if you alter the exhaust nozzle? Changes in engine performance and exhaust gas temperature
Why are small tabs placed in the engine exhaust nozzles of some engines? To correct exhaust gas temperature
An augmenter is classified as what type of engine? A ramjet engine
What is the purpose of a variable area orifice at the augmenter exhaust nozzle exit? TO schedule the nozzle area to obtain the desired thrust within the safe operating limits of the engine
What effect should augmenter operation have on engine operation? None
Define the term screech A condition of periodic violent pressure fluctuation in the augmenter duct, resulting from cyclic vibration due to the unsteady release of combustion energy
What two parts will most likely deteriorate or fail if moderate or severe screech is not checked? The flame holder or augmenter duct
How is screech controlled? By placing screech liners in the Augmenter duct
What 2 things does the flame holder in the augmenter do? Creates local turbulence and reduces the gas velocity in the vicinity of the flame
What are 2 drawbacks of the turbojet engine? Inefficient fuel use when flown below Mach 2 speeds and the amount of noise they generate
What makes the turbofan engine more desirable than basic turbojet engines? Capable of turbojet performance at higher speeds, while maintaining the shorter takeoff capability offered by the turboprop engine
What are the major sections of a turboprop engine? Reduction gearbox assembly, a torquemeter assembly, and a gas turbine power section
Created by: wcarrel11