Chapter 4 Section A - Engine Operation, Instruments, and Maintenance Flashcards
For an engine with a twin-spool compressor, what would the N1 and N2 tachometer indicate?
N1 - Speed of the low-pressure compressor
N2 - Speed of the high-pressure compressor
How is the R.P.M used in centrifugal compressors vs. axial-flow compressors?
RPM for centrifugal compressors - provides a direct indication of thrust being produced
RPM for axial-flow compressors - primarily to monitor engine speed during starting and to identify overspeed.
With turboprop engines that incorporate a free turbine, what is the difference between Ng and Np.?
Ng tachometer - indicates engine speed
Np tachometer - indicates propeller, or free-turbine speed
What is EPR?
Engine Pressure Ratio
Indicates the amount of thrust produced by comparing the relationship between turbine discharge pressure and compressor inlet pressure.
Turboprop and turboshaft engines often provide information about engine power output on a what?
Torquemeter guage
Why is fuel flow for a gas turbine engine indicated in pounds of fuel per hour?
Because the volume of jet fuel changes with temperature
What is
EGT
TIT
TOT
ITT
TGT?
Exhaust gas temperature (EGT) - Temperature guage that monitors the exhaust gas temperature.
Turbine inlet temperature (TIT) - guage that senses temperature at the inlet to the power turbines.
Turbine outlet temperature (TOT) - indicates the same information as EGT
Interstate turbine temperature (ITT) - indicates temperature between two turbine stages and directly proportional to TIT.
Turbine gas temperature (TGT)
What is EICAS?
Engine indicating and crew alerting system.
Displays all primary and secondary powerplant instruments such as EPR, N1, EGT, fuel flow, oil temperature, and engine vibrations. It also displays system faults and warning messages.
What are a few things that should be done to prepare for an engine run-up?
Place turbine engine in front of blast sheild
chock wheels and set brakes
remove inlet/exhaust covers
check proper levels for oil, fuel
Check for fuel leaks
Check for FOD’s
What guage normally is used to verify that the engine has started?
The EGT because of the sharp rise in temperature.
What is a hot start?
This occurs when an excessively rich fuel/air mixture is ignited. If continued, the EGT will excedd the operational limit and the engine will likely sustain damage. To minimize damage monitor the EGT, TIT, or ITT temperatures.
What is a hung start?
Occurs when the engine startup is normal and gas temperature is within limits, but the engine fails to accelerate or reach idle speed because:
- the starter cuts out too soon, or
- the starting power source fails to provide enough energy to rotate the engine at sufficient speed.
Turbine engine performance is based on standards established by the SAE.
- What is SAE?
- what are these standards also known as?
- Where can these standard be found?
- Society of Automotive Engineers.
- These standards are known as engine power ratings expressed in values of EPR, percent N1, or torque
- They are listed on an engine’s Type Certificate Data Sheet
What is takeoff power rating?
the amount of power that an aircraft engine is permitted to produce for takeoff
What is maximum continuous power?
a power level used at the discretion of the pilot for unusual or emergency situations. Depending on the engine model, maximum continuous power might be synonymous with maximum cruise power.
What is cruise power?
Throttle setting which provides the best fuel economy during flight and extended range. There is no time limit on this power setting.
When is an engine maximum climb power rating used?
used for normal climb to cruise altitude. This power rating is higher than cruise power and is not subject to time limitations
What is ground idle?
The lowest engine speed permitted for ground operations typically 50 to 70%. On a single spool engine it is indicated on the N1 tachometer. If the engine has more compressors, then it is indicated on the N2 or N3 tachometer.
What is flight idle?
the lowest engine speed permited in flight and is used primarily for descent, approach, and landing. Normally this speed is approximately 10 percent rpm higher than ground idle speed.
When the power output of an engine is intentionally limited to less than the maximum power that the engine can produce, the engine is said to be what?
Derated
What is a part-throttle engine vs. full-throttle engine?
Part throttle - engine produces takeoff thrust under standard sea-level conditions before the power lever is advanced to the full-throttle position
Full-throttle - takeoff power is obtained when the power lever is advanced to the full position on a standard sea level day.
What is the difference between line maintenance and shop maintenance?
Line maintenance - maiintenance that can be performed while the engine is installed on a aircraft
Shop maintenance - requires engine removal
What are the two ways for removing dirt and salt deposits from inside a turbine engine?
Fluid wash
Abrasive grit blast - uses Carboblast
What is trimming?
adjusting an engine’s fuel control unit
Engine parameters on most modern business jets and transport aircraft are displayed electronically on what?
LCD - Liquid crystal displays
CRT - cathod ray tubes
What can be done and used if an engine fire starts?
Cut off fuel flow
continue monotoring it with starter
Small amouts of CO2 can be discharged into inlet
What type of allen wrench is used to adjust Idle speed and maximum speed?
.125 (1/8) hex socket for idle speed
.1875 (3/16) hex socket for maximum speed
