Turbine Flashcards
at what point on an axial-flow turbojet engine will the highest gas pressure occur…?
at the compressor outlet
the rotor blades of an axial-flow compressors are usually made from what type of material?
Stainless steel
one function of the nozzle diaphram in a turbine engine is to?
direct the flow of gasses to strike the turbine blades at the desired angle
what is the profile of a turbine engine compressor blade?
a reduced blade tip thickness
the fan rotational speed of a dual axial compressor forward fan engine is the same as the…?
low pressure (LP) compressor
the abbreviation Pt7 used in turbine engine terminology means?
the total pressure at station 7
the bending of blades and vanes in a turbine engine…?
should be performed parallel to the length of the blade using smooth contors to minimise stress points
what turbine engine section provides for proper mixing of the fuel /air mixture?
combustion section
in a gas turbine engine, combustion occurs at a constant…?
pressure
which statement is true regarding jet engines?
at the higher engine speeds, thrust increases rapidly with small increases in RPM
some high volume turbo-prop and turbo-jet engines are equipped with two spol or split compressors. when these engines are operated at high alitiudes, the…?
low-pressure rotor will increase in speed as the compressor load decreases in the lower density air.
turbine nozzle diaphrams located on the upstream side of each turbine wheel, are used in the gas turbine engine to…?
increase the velocity of the heated gases flowing past the point.
where is the highest gas pressure in a turbojet engine?
the entrance of the burner section
an exhaust cone place aft of the turbine in a jet engine will cause the pressure in the first part of the exhaust duct to…?
increase and the velocity to decrease
what is the function of the stator vane assembly at the dicharge end of a typical axial-flow compressor?
to straighten airflow to eliminate turbulence
the turbine section of a jet engine drives…?
drives the compressor section
when starting a turbine engine?
a hot start is indicated if the exhause gas temps exceed specified limits
in the dual axial-flow or twin spool compressor system, the first stage turbine drives the …?
N2 compressor
which of the following may be used to mark turbine engine components exposed to high temps?
layout die
when starting a turbine engine, a hung start is indicated if the engine?
fails to reach idle RPM
what are the two basic elements of the turbine section in a turbine engine?
stators and rotors
which of the following acts as a diffuser in a turbine engine and converts velocity to pressure?
Stators
The function of the exhaust cone assembly of a turbine engine is to?
Straighten and collect the exhaust gases into a solid exhaust jet
What are the two functional elements in a centrifugal compressor?
impeller and diffuser
The components of a centrifugal compressor section consist of the impeller, diffuser and?
Manifold
What must be done after the fuel control unit has been replaced on an aircraft gas turbine engine?
Retrim the engine
If, during inspection at engine overhaul, ball or roller bearings are found to have magnetism, but otherwise have no defects, they?
Must be degaussed before use
A turbine engine compressor which contains vanes on both sides of the propeller is a…?
double entry centrifugal compressor
What is the first engine instrument indication of a successful start of a turbine engine?
A rise in exhaust gas temperature
Some engine manufacturers of twin spool gas turbine engines identify turbine discharge pressure in their maintenance manuals as…?
Pt7
Who establishes the recommended operating time between overhauls of a turbine engine used in general aviation?
the engine manafacture
Turbine engine components exposed to high temperatures generally may not be marked with?
Wax, grease pencil or a graphite lead pencil
Who establishes mandatory replacement times for critical components of a turbine engine?
The engine manufacturer
Main bearing oil seals used with turbine engines are usually what type?
Labyrinth and/or carbon rubbing
How does a dual axial-flow compressor improve the efficiency of a turbo jet engine?
Higher compression ratios can be obtained
Three types of turbine blades are?
Impulse, reaction, and impulse-reaction
Which statements are true regarding aircraft engine propulsion?
An engine driven propeller imparts a relatively small amount of acceleration to a large mass of air
The basic gas turbine engine is divided into two main sections. the cold section and the hot section.
1. The cold section includes the engine inlet, compressor, and the turbine sections
2. The hot section includes the combuster, diffuser, and exhaust sections
NEITHER 1 NOR 2 is true
- Welding and straightening of turbine engine rotating airfoils does not require special equipment
- Welding and straightening of turbine engine rotating airfoils is commonly recommended by the manafacture
NEITHER 1 NOR 2 are true
The advantage of the axio flow compressor is its?
High peak efficiency
What is one purpose of the stator blades in the compression section of the turbine engine?
To control direction of the air flow
What is the purpose of the diffuser section in a turbine engine?
To increase pressure and reduce velocity
Where do stress rupture cracks usually appear on turbine blades?
Across the leading edge or trailing edge at right angles to the edge length
In which type of turbine engine combustion chamber is the case and liner are removed and installed as one unit during routine maintenance?
Can
The diffuser of a jet engine is located between?
The compressor section and the burner section
When the leading edge of a first stage, turbine blade is found to have stress rupture cracks, which of the following should be suspected?
Overtemp condition
Turbine blades are generally more susceptible to operating damage than compressor blades because of?
The exposure to high temps
Which of the following is the ultimate limiting factor of a turbine engine operation?
Turbine inlet temperature
The recurrent ingestion of dust or other fine airborne particles into a turbine engine can result in?
Erosion damage to the compressor and turbine sections
Which of the following engine variables is the most CRITICAL during turbine engine operation?
Turbine inlet temperature
Reduced blade vibration and improved airflow characteristics in gas turbine engines are brought about by?
Shrouded turbine rotor blades
Which turbine engine compressor offers the greatest advantages for both starting flexibly and improved high altitude performance?
Split-spool, axial-flow
Jet engine turbine blades removed for detailed inspection must be installed in?
in the same spot
An advantage of the centrifugal-flow compressor is its high?
pressure rise per stage
the highest heat-to-metal contact in the jet engine is the …?
turbine inlet guide vanes
Which two elements make up the axial-flow compressor assembly?
Rotor and stator
The two types of centrifugal compressor impellers are?
Single entry and double entry
Between each row of rotating blades in a turbine engine compressor, there is a row of stationary blades which act to defuse the air. These stationary blades are called?
Stators
standard sea level pressure is…?
29.92” Hg
Using standard atmospheric conditions, the standard sea level temperature is?
59°F
When aircraft turbine blades are subjected to excessive heat stress, What type of failures would you expect?
Stress rupture
In an axial-flow compressor, one purpose of the stator vanes at the discharge end of the compressor is to?
Straighten the air flow and eliminate turbulence
Compressor field cleaning on a turbine engine is performed primarily in order to?
Prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surface
Hot section inspections for many modern turbine engines are required?
On a time or cycle basis
The purpose of the shrouds on the turbine blades of an axial-flow compressor engine is to?
reduce vibration
In a dual axial-flow compressor, the first stage turbine drives?
N2 compressor
What should be done initially if a turbine engine catches fire when starting?
Turn off the fuel and continue engine rotation with the starter
What is the proper starting sequence for a turbo jet engine?
Starter, ignition, fuel
A weak fuel to air mixture along with normal airflow through a turbon engine may result in?
A lean die-out
Turbine engine flame out may be caused by improper….?
Fuel/air mixture
Turbine engine after flame is caused by?
Excess fuel in the combustion section, turbine or exhaust nozles
What is used in turbine engines to aid in stabilization of compressor airflow during low thrust engine operation
Variable guide vanes and/or compressor bleed valves
Name the working fluid that provides pressure to the variable inlet guide vane actuators used on some turbine engine compressors…?
hydraylic fluid
In a turbo engine with a dual spool compressor, the low speed compressor…?
seeks its own best operating speed
What is the function of the inlet guide vane assembly on an axial-flow compressor?
Direct the air flow into the first stage rotor blades at the proper angle
Which of the following is a good indication of a malfunctional fuel nozzle when inspecting the exhaustion of an aircraft turbine engine?
Hot spots on the tail cone
The stator vanes on an axial-flow compressor…?
convert velocity energy into pressure energy
The velocity of SUBSONIC air as it flows through a convergent nozzle?
Increases
The velocity of SUPERSONIC air as it flows through a diversion nozzle…?
Increases
The velocity of supersonic air as it flows through a diversion puzle.
Decreases
The pressure of SUBSONIC air as it flows through a convergant nozzle..?
Decreases
Anti icing of jet engine air inlets is commonly accomplished by?
Engine bleed air ducted through the critical areas
Generally, when starting a turbo engine, the starter should be disengaged?
When the engine has reached self accelerating speed
What is the primary advantage of an axial-flow compressor over a centrifugal compressor?
Greater pressure ratio
The purpose of bleed valves, located in the beginning stages of the compressor, in an aircraft gas turbine engine is to?
Vent some of the air overboard to prevent a compressor stall
What is meant by a double entry centrifugal compressor?
a compressor with vanes on both sides of the impeller
What is the major function of the turbine assembly in a turbo jet engine?
Supplies the power to turn the compressor
Stator blades in the compressor section of an axial-flow turbine engine?
Decrease the air velocity and prevent swirling
Gas turbine engine comprises of which three main sections?
Turbine, compressor, combustion
What type of turbine blade is most commonly used in aircraft jet engine…?
Impluse-reaction
What is the primary factor which controls the pressure ratio of an axial-flow compressor?
Number of stages in the compressor
The non rotating axial-flow compressor airfoils in an aircraft gas turbine engine are called?
Stator vanes
- in a turbine engine axial-flow compressor, each consecutive pair of roter and stator blades constitutes a pressure stage.
- in a turbine engine axial-flow compressor, the number of rows of stages is determined by the amount of air and total pressure rise required.
BOTH 1 and 2 are true
The air passing through the combustion chamber of a turbine engine is?
Used to support combustion and to cool the engine
The stators in a turbine engine section of a gas turbine engine?
Increase velocity of the gas flow
The compressor stators in a gas turbine engine act as diffusers to?
Decrease the velocity of the gas flow
The procedure for removing the accumulation of dirt deposits on compressor blades is called?
Field cleaning
Which of the following may be used to accomplish an internal inspection of an assembled turbine engine?
A boroscope
What is the possible cause when a turbine engine indicates no change in power setting parameters, but the oil temperature is high…?
Enigne main bearing distress
Newton’s first law of motion generally termed as the law of inertia states?
Every body persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force
Newton’s second law of motion generally termed as law of momentum states:
Acceleration is produced when a force acts on a mass.
The greater the mass, the greater amount of force needed
A turbine engine hot section is particularly susceptible to which kind of damage?
Cracking
Dirt particles in the air being introduced into the compressor of a turbine engine will form coating on all but which of the following?
Turbine blades
Severe rubbing of turbine engine compressor blades will usually cause?
Galling
Which of the following influences the operation of an automatic fuel control unit on a turbojet engine?
Burner pressure
If a turbine engine is unable to reach, take off EPR before its EGT limit is reached, this is an indication that the?
compressor may be damaged or contaminated
The Brayton Cycle is known as the constant …?
Constant pressure cycle
Continued and/or excessive heat and centrifugal force on a turbine engine rotor blade is likely to cause?
Creep
If the RPM of an axial-flow compressor remains constant, the angle of the attack of the rotor blade can be changed by?
Changing the velocity of the airflow
The compression ratio of an axial-flow compressor is the function of the?
Number of compressor stages
Which of the following variables affect the inlet air density of a turbine engine?
Speed of the aircraft, altitude of the aircraft, and ambient temperature
Which of the following factors affect a thermal efficiency of a turbine engine?
Turbine inlet temp, compressor ratio, turbine and compressor efficiency
Why do some turbine engines have more than one turbo wheel attached to a single shaft??
to extract more power from the exhaust gasses than a single wheel can absorb
The exhaust section of a turbine engine is designed to?
Impart high exit velocities to the exhaust gases
Which Of the following types of combustion sections are used in turbine engines?
Multiple can, annular, can-annular
A cool-off period prior to shutdown of a turbine engine is accomplished in order to?
too allow the turbine wheel to cool down before the case contracts around it
What type of igniter plug is used in the low tension ignition system of an aircraft turbofan engine?
self-ionizing or shunted-gap plug type
What is meant by a shrouded turbine?
the turbine blades are shaped so their ends form a band or shroud.
What time is used to describe a permanent and cumulative deformation of the turbine blades of a turbojet engine?
creep
What is the purpose of the dump valve used on aircraft gas turbine engines?
The fuel is quickly cut off to the nozzles and the manifold are drained, preventing fuel boiling as a result of residual engine heat
At what stage in a turbine engine are gas pressures the greatest?
Compressor outlet
In what section of a turbojet engine is the jet nozzle located?
EXHAUST
- Accumulation of contaminants in the compressor of a turbojet engine reduces aerodynamic efficiency of the blades.
- Two common methods for removing dirt deposits from turbojet engine compressor blades are a fluid wash and an abrasive grit blast.
BOTH 1 and 2 are true
Hotspots in the combustion section of turbojet engine are possible indicators of?
Malfunctioning fuel nozzles
Which of the following can cause fan blade shingling in the turbo fan engine?
Engine overspeed and/or FOD
Compressor stall is caused by
A High angle of attack airflow through the first stages of compression
The condition known as “hot streaking” in turbine engines is caused by?
A partially clogged fuel nozzle
Refer to figure 1…
Determine which portion of the AD is applicable for Model O-690 series engines, serial No. 5863-40 with 283 hours time in service?
B, 1.
A Cessna 180 aircraft has a McCauley propeller Modle No. 2A34C50/90A. The propeller is severely damaged in a ground accident, and this model propeller is not available for replacement. Which of the
following should be used to find an approved alternate replacement?
Aircraft Specifications/Type Certificate Data Sheets
A Maule M-7-235 has a Lycoming 0-540-J1A5P and a Hartzell HC-C2YR-1BF/F8468A-6R. Where can you
find if this is an approved engine/propeller combination?
Aircraft Specifications/Type Certificate Data Sheet.
Which of the following is used to monitor the mechanical integrity of the turbo engines, as well as to check the engine operation conditions of a turbine engine?
Exhaust gas Temp EGT
What instrument on a gas turbine engine should be monitored to minimize the possibility of a hot start?
Turbine inlet temp
In regard to using a turbine engine oil analysis program, which of the following is NOT true?
Generally, accurate trend forecast may be made after an engines first oil sample analysis
In an aircraft turbine engine operating at a constant power, the application of the engine anti icing will result in?
a noticeable shift in engine EPR
Engine pressure ratio EPR is the total pressure ratio between?
The front of the compressor and the rear of the turbine.
What would be the possible cause if the gas turbine engine has high exhaust gas temperatures, high fuel flow, and low rpm at all engine power settings?
Turbine damage or loss of turbine efficiency
What is the primary purpose of a tachometer on an axial-compressor turbine engine?
To monitor RPM during starting and to indicate overspeed conditions
Engine pressure ration EPR indicator is a direct indication of?
Engine thrust being produced
The exhaust gas temperature EGT indicator on a gas turbine engine provides a relative indication of the?
turbine inlet temp
what instrument indicates the thrust of a gas turbine engine?
Engine pressure ratio EPR
in a turbine engine, where is the turbine discharge pressure indicator sensor located?
Immediatley aft of the last turbine stage
in what units are the turbine engine tachometers calibrated?
Percentage of engine RPM
Instruments that provide readings of low or negative pressure, such as manifold pressure gauges, are usually what type?
Diaphragm or bellows
Instruments that measure relatively high fluid pressure, such as oil presure gauges, are uaually what type?
Bourdon tube
The RPM indication of a synchronous AC motor-tachometer is governed by the generator…?
Frequency
How are most turbine engine fire extinguishing systems activated?
Electrically discharged cartridges
One way that the automatic ignition relight systems are activated on gas turbine engines is by a?
A drop in compressor discharge pressure
When the starter switch to an aircraft gas turbine engine starter-generator is energized and the engine fails to rotate, one of the probable causes would be the?
The starter solenoid is defective
Which of these characteristics is desirable in turbine engine oil?
High Flash Point
The viscosity of a liquid is a measure of its?
Resistance to flow
What type of oil system is usually found on a turbine engine?
Dry sump, Pressure, Spray
Which of the following helps determine the proper grade of oil to be used in a particular engine?
Operating speed of the bearings
The type of oil pumps most commonly used on turbulent engines are classified as?
Positive displacement pumps
In a jet engine which uses a fuel oil heat exchanger, the oil temperature is controlled by a thermostatic valve that regulates the flow of the?
Oil through the heat exchanger
- Fuel may be used to cool oil in gas turbine engines.
- Ram air may be used to cool oil and gas turbine engines
BOTH 1 and 2 are True
In an axial-flow turbine engine, compressor bleed air is sometimes used to aid in cooling the?
Turbine, Vanes, Blades and Bearings
Oil picks up the most heat from which of the following turbine engine components?
Turbine bearing
Which of the following is a function of the fuel/oil heat exhanger on a turbojet engine?
Increase fuel temp
After making it welded repair to a pressurised type turbine oil tank, the tank should be pressure checked to?
not less than 5 PSI plus the MAXIMUM operating pressure of the tank
Why are fixed orifice nozzles used in the lubrication system of gas turbine engines?
To provide a relatively constant oil flow to the main tank bearing at all engine speeds
Possible failure related ferrous metas particals in turbine engine oil cause an (electrical) indicating type magnetic chip detector to indicate their presence by?
Bridging the gap between the detector center (positive) electrode and the ground electrode (negative)
What would be the probable result if the oil system pressure relief fail should stick in the OPEN position?
Insufficient lubrication
According the the Federal Aviation Regulations (FARs), oil tank fillers on turbine engines must be marked with the word…?
OIL
What is the primary purpose of the oil breather pressurisation system that is used on turbine engines?
Provide a proper oil spray pattern from the main bearing oil jets
The purpose of directing bleed air to the outer turbine case on some engines is to…?
Provide optimum turbine blade tip clearance by controlling thermal expansion
In order to relieve excessive pump pressure in an engine’s internal oil system, most engines are equipped with a?
Relief Valve
What is the purpose of the check valve generally used in a dry sump lubrication system?
To prevent the oil from the supply tank from seeping into the crankcase during inoperative periods
Which of the following factors has the least effect on oil consumption of a specific engine?
Mechanical efficiency
How is the oil collected by the piston oil ring returned to the crankcase?
through holes drilled in the piston oil ring groove
Which of the following lubrication system components is never located between the pressure pump and the engine pressure system?
fuel line for oil dilution system
As an aid to cold weather starting, the oil dilution systems thins the oil with…?
Gasoline
The basic oil pressure relief valve setting for a newly overhauled engine is made in?
In the overhaul shop
Where is the oil temp bulb located on a dry sump reciprocating engine ?
Oil Inlet Line
Cylinder walls are usually lubricated by…?
Splashed or sprayed oil
if an oil filter element becomes completely clogged, the bypass…?
The bypass valve will open, and the oil pump will supply unfiltered oil
Oil accumulating in the cylinders of an inverted in line engine and in the low cylinders of a radial engine is normally reduced or prevented by?
Extended cylinder skirts
What is the primary purpose of changing aircraft engine lubricating oils at predetermined periods?
The oil becomes contaminated with moisture, acids, and finely divided suspended solid particals
What determines the minimum particle size, which will be excluded or filtered by a cuno type (stacked disc edge filtration) filter?
The spacer thickness
What is the primary purpose of the hopper located in the oil supply tank of some dry sump engine installations?
To reduce the time required to warm the oil to operating temps
The purpose of the flow control valve in a reciprocating engine oil system is to?
Direct the oil through or around the oil cooler
Where are sludge chambers, when used in aircraft engine lubrication systems, usually located?
in the crankshaft throws
Why is an aircraft reciprocating engine oil tank on a dry sump lubrication system equipped with a vent line?
To prevent pressure build up in the oil tank
Excessive oil is prevented from accumulating on the cylinder walls of a reciprocating engine by?
oil control rings on the piston
- Wet sump oil systems are most commonly used in gas turbine engines ❌️
- In most turbine engine oil tanks, a slight pressurization of the tank is designed to ensure a positive flow of oil.✔️
ONLY 2 is true
The pumping capacity of the scavenger pump in a dry sump aircraft engines lubrication system is?
Is greater than the capacity of the oil supply pump
In which of the following situations will the oil cooler automatic bypass valve be open the greatest amount?
Engine below normal operating temps
A turbine engine dry sump lubrication system of the self contained, high pressure design consists of?
consists of pressure, breather, and scavenger subsystems
Lube system last chance filters in turbine engines are usually cleaned?
during overhaul
The purpose of a relief valve installed in the tank venting system of a turbine engine oil tank is to?
Prevent oil pump cavitation by maintaining a constant pressure on the oil pump inlet
As a general rule, a small amount of fuzy particles or gray metallic paste on the turbine engine magnetic chip detector is considered?
Is considered to be the result of normal wear
The purpose of a dwell chamber in a turbine engine oil tank is to provide?
Seperation of entrained air from scavenged oil
Which of the following bearing types must be continuously lubricated by pressure oil?
Plain
A capacity type ignition system is used almost universally on turbine engines, primarily because of its high voltage and…?
High Heat Intensity
How does the ignition system of a gas turbine engine differ from that of a reciprocating engine?
A high energy spark is required for ignition.
In a turbine engine DC capacitor discharge ignition system, where are the high voltage pulses formed?
at the triggering transformer
Why are turbine engine igniters less susceptible to fouling than reciprocating engine spark plugs?
The high intensity spark cleans the ignitor.
To prevent seizing of the igniter plug the threads in many cases are?
Lubricated with an anti seize compound
To prevent seizing of the ignitor plugs the threads in many cases are?
silver plated
igniter plugs have nickel chromium plating for?
High heat and corrosion resistance
The constrained gap igniter plug used in some gas turbine engines operates at a cooler temp because of?
The construction is such that the spark occurs beyond the face of the combustion chamber liner
Generally, when removing a turbine engine ignited plug in order to eliminate the possibility of the technician receiving a lethal shock, the ignition switches is turned off and?
The ignitor lead is disconnected from the plug and the center electrode grounded to the engine after disconnecting the transformer-exciter input lead and waiting the prescribed time.
Great caution should be exercised in handling damaged hermetically sealed turbine engine ignitor transformer units because?
Some contain ratioactive material
Igniter plug used in turbine engines have a long service life because they?
They do not require continuous operation
