Operating Theory 1
Standard sea level pressure is what?
29.92" Hg
ASA 8163
Standard sea level temperature is what?
59 degrees Fahrenheit.
ASA 8164
In a dual axial-flow or twin spool compressor system, the first stage turbine drives what?
The N2 compressor.
ASA 8124
Name the three types of turbine blades.
Impulse, Reaction, and Impulse-Reaction.
ASA 8142
If the engine fails to reach idle RPM when starting a turbine, this indicates what?
A hung start.
ASA 8126
What may be used to mark turbine engine components exposed to high temperatures?
Layout dye
ASA 8125
The APU receives its supply of fuel from what?
The aircraft's main fuel tank.
ASA 8998
Turbine inlet temperature is the ultimate what of turbine engine operation?
Limiting factor.
ASA 8152
The stator and rotor as the two basic elements of what section of a turbine engine?
Turbine section.
ASA 8127
The turbine inlet guide vanes have the highest what in a jet engine?
Heat-to-metal contact.
ASA 8159
Stators act as what and converts what in a turbine engine?
Acts as a diffuser and converts velocity to pressure.
ASA 8127-1
What are the two functional elements in a centrifugal compressor?
Impeller and Diffuser.
ASA 8129
What must be degaussed before use if found to have magnetism during inspection at engine overhaul?
Ball or Roller Bearings
ASA 8131
The engine manufacturer establishes the recommended what of a turbine engine used in general aviation?
Operating Time Between Overhauls (TBO)
ASA 8135
An APU is usually rotated during start by what?
An electric starter.
ASA 8999
A rise in the exhaust gas temperature is the first what of a successful start of a turbine engine?
engine instrument indication.
ASA 8133
The highest gas pressure occurs at what point in an axial-flow turbojet engine?
At the compressor outlet.
ASA 8108
The abbreviation Pt7 means what?
Total pressure at station 7.
ASA 8112
What is the function of the exhaust cone assembly?
Straightens and collects exhaust gases into a solid exhaust jet.
ASA 8128
A double entry centrifugal compressor contains vanes on both sides of what?
The impeller.
ASA 8132
The engine manufacturer establishes what for critical components of turbine engines?
Mandatory Replacement Times.
ASA 8139
Where do stress rupture cracks usually appear on turbine blades?
Across the leading or trailing edge at a right angle to the edge length.
ASA 8147
Most of the load placed on the APU occurs when the ________ is opened.
Bleed Air Valve.
ASA 9004
Can combustion chambers require what to be removed and installed as one unit during maintenance?
the case and liner.
ASA 8148
The combustion section provides what in a turbine engine?
Proper mixing of the fuel and air.
ASA 8114
The velocity and pressure of supersonic air as it flows through a divergent nozzles does what?
Velocity increases
Pressure decreases
ASA 8180 and 8182
What is the profile of a turbine compressor blade?
A reduced blade tip thickness.
ASA 8110
The two types of centrifugal compressor impellers are what?
Single entry and double entry.
ASA 8161
Stress ruptures are the result when turbine blades are subjected to what?
excessive heat stress.
ASA 8165
Jet engine turbine blades that are removed for detailed inspection must be reinstalled how?
In the same slot.
ASA 8157
The primary function of a __________ is to provide bleed air for aircraft pneumatic systems.
Load Compressor.
ASA 9006
TRUE OR FALSE?
At higher engine speeds, thrust increases rapidly with a small increase in RPM.
True
ASA 8116
The velocity and pressure of subsonic air as it flows through a convergent nozzle does what?
Velocity increases
Pressure decreases
ASA 8179 and 8181
Name the three main sections that comprise a gas turbine engine.
Turbine, Compressor, and Conbustion.
ASA 8190
Labyrinth and/or carbon rubbing are the types used on this part in turbine engines.
ASA 8140
High peak efficiency is an advantage of what kind of compressor?
Axial-flow.
ASA 8144
How should the blending of blades and vanes be performed in a turbine engine?
Parallel to the length of the blade using smooth contours to minimize stress points.
ASA 8113
What can cause erosion damage to the compressor and turbine sections of an engine?
ASA 8153
What is frequently identical to the engine-driven generators in an aircraft?
The Auxiliary Power Unit (APU) generator.
ASA 8997
What two components are split into two sections on a turbine with dual-spool, axial-flow compressor?
The compressor and the high-pressure turbine.
ASA 9009
TRUE OR FALSE?
An engine-driven propeller imparts a relatively small amount of acceleration to a small mass of air.
False; An engine-driven propeller imparts a small amount of acceleration to a LARGE mass of air.
ASA 8143
TRUE OR FALSE?
The air passing through the combustion chamber of a turbine engine is used to support ignition and to control air flow.
False; used to support combustion and to cool the engine.
ASA 8195
What directs the flow of gases to strike the turbine engine?
The nozzle diaphragm.
ASA 8109
Turbine nozzle diaphragms located on the upstream side of the turbine wheel are used to increase the velocity of what?
The velocity of heated gases flowing past this point.
ASA 8118
What should be done initially if a turbine engine catches fire when starting?
Turn off the fuel and continue engine rotation with the starter.
ASA 8171
What causes fan blade shingling in a turbofan engine?
Engine over speed and/or FOD.
ASA 8225
TRUE OR FALSE?
The speed of an APU remains at or near rated speed when placed under a load when in operation.
False; Remains at or near rated speed regardless of load condition.
ASA 9001
Name the sections that make up the cold section of a turbine engine.
Engine inlet, Diffuser, and Compressor.
ASA 8136
The constant pressure cycle is also known as what?
The Brayton cycle.
ASA 8207
Burner pressure influences the operation of what in a turbojet engine?
The automatic fuel control unit.
ASA 8205
What is located between the compressor section and the burner section of a turbine engine?
The diffuser section.
ASA 8149
Name the two purposes of having stator vanes at the discharge end of an axial-flow compressor.
Straighten airflow
Eliminate turbulence
ASA 8166
Hotspots on the tail cone are a good indication of what when inspecting the exhaust section of an aircraft engine turbine?
A malfunctioning fuel nozzle.
ASA 8177
Creep is used to describe what in a turbojet engine?
A permanent and cumulative deformation of the turbine blades.
ASA 8219
Pneumatic loading will be automatically modulated to maintain a safe EGT when pneumatic power is used in conjunction with what?
Maximum APU shaft output power.
ASA 9002
If a turbine engine is unable to reach takeoff EPR before its EGT limit is reached, this is an indication of what?
The compressor may be contaminated or damaged.
ASA 8206
Name three variables that affect the inlet air density of a turbine engine.
Speed of the aircraft
Altitude of the aircraft
Ambient temperature
ASA 8211
What is the major advantage of having multiple turbine wheels on a single shaft?
Extracts more power from the exhaust gases than a single turbine wheel can absorb.
ASA 8213
Shrouded turbine rotor blades reduce _____ and improve _______ in gas turbines.
ASA 8155
Name either or both components that aid in stabilization of compressor airflow during low thrust engine operation.
Variable guide vanes
and/or
Compressor bleed valves
ASA 8174
TRUE OR FALSE?
Welding or straightening of the turbine engine rotating airfoils is typically authorized by the engine manufacturer.
False, it is typically not authorized by the manufacturer.
ASA 8137
What two methods are used for removing dirt deposits from turbojet engine compressor blades?
A fluid wash and an abrasive grit blast.
ASA 8223
Closing the bleed air valve accomplishes what when necessary?
APU engine cooling before shutdown.
ASA 9003
Some engine manufacturers of twin spool gas turbines identify turbine discharge pressure in their maintenance manuals as what?
Pt7
ASA 8134
Gas pressures are the highest at what point in a turbine engine?
The compressor outlet.
ASA 8221
What is the purpose of the dump valve in a turbine engine?
Quickly cuts off fuel to the nozzles and drains the manifolds to prevent the fuel from boiling off due to residual heat.
ASA 8220
Each _______ pair of rotor blades and stator vanes constitutes a pressure stage.
Consecutive
ASA 8194
What type of turbine blade is most commonly used in jet engines?
Impulse-Reaction.
ASA 8191
Compressor field cleaning on turbine engines is performed primarily to prevent three reasons. What are they?
engine performance degradation
Increased fuel costs
Damage or corrosion to gas path surfaces
ASA 8167
What is a lean die-out?
A weak fuel to air mixture along with normal air flow through a turbine engine.
ASA 8173
What stabilizes the pressure of the air before it enters the compressor?
The APU air inlet plenum.
ASA 9000
What happens when high-volume turboprop and turbojet engines that are equipped with two-spool or split compressors are operated at high altitudes?
The low-pressure rotor will increase in speed as the compressor load decreases in the lower density air.
ASA 8117
TRUE OR FALSE?
The three types of combustion sections used in turbine engines is Can, Annular, and Can-Annular.
True
ASA 8215
Name four factors that affect thermal efficiency of a turbine engine.
Turbine inlet temperature
Compression ratio
turbine efficiency
compressor efficiency
ASA 8212
What type of igniter plug is used in the low tension ignition system of an aircraft turbofan engine?
Self-ionizing or shunted-gap type plug.
ASA 8217
Stator blades in the compressor section of an axial-flow turbine decreases the air velocity and _______.
Prevents Swirling.
ASA 8189
Explain Hot Streaking in turbine engines.
(Double points if you can successfully explain it without looking it up)
A hot section condition in which the flame penetrates through the entire turbine system to the tail pipe. Usually caused by a partially clogged fuel nozzle which does not atomize the fuel into a cone-shaped pattern, but rather, allows a small fuel stream to flow with sufficient force to cut through the cooling air blanket and impinge directly on the turbine surfaces.
ASA 8227
What is the possible cause when a turbine engine indicates no change in power setting parameters, but oil temperature is high?
Engine main bearing distress.
ASA 8200
The APU fuel control system automatically maintains what?
Fuel servicing:
-During APU start
-Under varying pneumatic bleed and electrical loads
ASA 9005
What are the greatest advantages of a split-spool, axial-flow turbine engine compressor?
ASA 8156