Chapter 4 Section A - Engine Operation, Instruments, and Maintenance

Question 1

For an engine with a twin-spool compressor, what would the N1 and N2 tachometer indicate?

Answer 1

N1 - Speed of the low-pressure compressor

N2 - Speed of the high-pressure compressor

Question 2

How is the R.P.M used in centrifugal compressors vs. axial-flow compressors?

Answer 2

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.

Question 3

With turboprop engines that incorporate a free turbine, what is the difference between N_g and N_p.?

Answer 3

N_g tachometer - indicates engine speed

N_p tachometer - indicates propeller, or free-turbine speed

Question 4

What is EPR?

Answer 4

Engine Pressure Ratio

Indicates the amount of thrust produced by comparing the relationship between turbine discharge pressure and compressor inlet pressure.

Question 5

Turboprop and turboshaft engines often provide information about engine power output on a what?

Answer 5

Torquemeter guage

Question 6

Why is fuel flow for a gas turbine engine indicated in pounds of fuel per hour?

Answer 6

Because the volume of jet fuel changes with temperature

Question 7

What is

EGT

TIT

TOT

ITT

TGT?

Answer 7

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)

Question 8

What is EICAS?

Answer 8

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.

Question 9

What are a few things that should be done to prepare for an engine run-up?

Answer 9

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

Question 10

What guage normally is used to verify that the engine has started?

Answer 10

The EGT because of the sharp rise in temperature.

Question 11

What is a hot start?

Answer 11

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.

Question 12

What is a hung start?

Answer 12

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.

Question 13

Turbine engine performance is based on standards established by the SAE.

1. What is SAE?
2. what are these standards also known as?
3. Where can these standard be found?

Answer 13

1. Society of Automotive Engineers.
2. These standards are known as engine power ratings expressed in values of EPR, percent N1, or torque
3. They are listed on an engine’s Type Certificate Data Sheet

Question 14

What is takeoff power rating?

Answer 14

the amount of power that an aircraft engine is permitted to produce for takeoff

Question 15

What is maximum continuous power?

Answer 15

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.

Question 16

What is cruise power?

Answer 16

Throttle setting which provides the best fuel economy during flight and extended range. There is no time limit on this power setting.

Question 17

When is an engine maximum climb power rating used?

Answer 17

used for normal climb to cruise altitude. This power rating is higher than cruise power and is not subject to time limitations

Question 18

What is ground idle?

Answer 18

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.

Question 19

What is flight idle?

Answer 19

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.

Question 20

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?

Answer 20

Derated

Question 21

What is a part-throttle engine vs. full-throttle engine?

Answer 21

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.

Question 22

What is the difference between line maintenance and shop maintenance?

Answer 22

Line maintenance - maiintenance that can be performed while the engine is installed on a aircraft

Shop maintenance - requires engine removal

Question 23

What are the two ways for removing dirt and salt deposits from inside a turbine engine?

Answer 23

Fluid wash

Abrasive grit blast - uses Carboblast

Question 24

What is trimming?

Answer 24

adjusting an engine’s fuel control unit

Question 25

Engine parameters on most modern business jets and transport aircraft are displayed electronically on what?

Answer 25

LCD - Liquid crystal displays

CRT - cathod ray tubes

Question 26

What can be done and used if an engine fire starts?

Answer 26

Cut off fuel flow

continue monotoring it with starter

Small amouts of CO2 can be discharged into inlet

Question 27

What type of allen wrench is used to adjust Idle speed and maximum speed?

Answer 27

.125 (1/8) hex socket for idle speed

.1875 (3/16) hex socket for maximum speed