Powerplant Oral questions

Question 1

What is the purpose of dynamic dampers on crankshafts?

Answer 1

They reduce engine vibration

Question 2

What types of bearings are generally found in reciprocating engines?

Answer 2

Plain, Ball, and Roller bearings

Question 3

Are the connecting rods used in each cylinder of a radial engine the same? Explain.

Answer 3

No. Radial engines use master and articulating rod assemblies

Question 4

Name the different types of piston rings

Answer 4

Oil control, Compression, and oil scraper

Question 5

Where should piston ring gaps be installed relative to each other, and Why?

Answer 5

Compression ring gaps should be staggered so that they do not align. This prevents excessive blow-by

Question 6

What could result from incorrectly installed piston rings?

Answer 6

Excessive oil consumption

Question 7

What purpose do oil control rings serve?

Answer 7

They regulate the thickness of the oil film on the cylinder walls

Question 8

What is used to help prevent valve surge or floating in an aircraft engine?

Answer 8

Two or more springs are used on each valve

Question 9

On engines equipped with hydraulic valve lifters, what should the running valve clearance be?

Answer 9

Zero

Question 10

What is the purpose of valve overlap?

Answer 10

It allows better volumetric efficiency and lowerss cylinder operating temperatures

Question 11

What indications are given in the event of a leaking or open primer while the engine is running?

Answer 11

The engine will not idle properly

Question 12

When pulling a propeller through, a hissing sound is heard, indicating valve blow-by. What procedure should be performed next?

Answer 12

A compression check should be performed to identify the faulty cylinder

Question 13

What is the purpose of performing a compression test?

Answer 13

To determine if the valves, pistons and rings are sealing properly

Question 14

When an engine is overhauled, how is its total time affected? When an engine is rebuilt, how is its operating history affected?

Answer 14

The total time on the engine must be continued and the time since major overhaul is entered into the engine log. If the manufacturer rebuilds the engine, it is granted a zero-time status and is considered to have no previous operating history

Question 15

What inspections should be performed after a propeller strike without sudden stoppage?

Answer 15

1. Inspect engine mounts, the crankcase and the nose section for damage. 2. Inspect the oil and oil filters/screens for metal particles 3. inspect thee crankshaft or driveshaft for cracks and mis alignment

Question 16

Name some of the precautions that should be performed prior to engine removal

Answer 16

Disconnect the battery turn off the fuel valves, chock the wheels, and if necessary install a tail stand

Question 17

When inspecting a piston, where are cracks most likely to be found?

Answer 17

In those areas that are highly stressed; usually the base of the piston bosses, inside at thee junction of the bore and the walls, and the ring lands

Question 18

What does it mean if an engine part is within “serviceable limits”?

Answer 18

It means that the part is within the manufacturers limits and can be used in an engine (does not require replacement)

Question 19

What tools or instruments are used to inspect a cylinder barrel for out-of-roundness

Answer 19

A dial indicator or an inside micrometer is usually used to measure the top of the cylinder and at the skirt. A telescopic gauge and micrometer can also be used two readings should be taken 90 degrees to each other

Question 20

How can a loose stud in an engine crankcase be repaired?

Answer 20

Remove the loose stud and inspect the hole for size and thread condition. It may be necessary to use an oversize stud or Heli-coil insert

Question 21

What publication is used to check an engine for normal operation?

Answer 21

Manufacturers Maintenance Manual

Question 22

A weak cylinder is found during a compression check. What must be inspected?

Answer 22

Pressure is transmitted equally in all directions

Question 23

What purpose does an oil analysis serve?

Answer 23

Metal particles in the oil show normal and abnormal wear of the engine. This helps in evaluating the engines internal condition

Question 24

What inspection should be performed on an engine that has been in storage?

Answer 24

Perform an inspection to determine if there is any corrosion damage

Question 25

Where would a carburetor air temperature bulb be located?

Answer 25

In the ram air intake duct

Question 26

What is the fuel pressure range on float-type carburetors?

Answer 26

3-5 psi

Question 27

Name the basic components of a fuel indicator

Answer 27

The transmitter and the indicator

Question 28

What unit of measure is generally used to indicate fuel flow?

Answer 28

Pounds or Gallons per hour

Question 29

Why is fuel flow monitored?

Answer 29

To determine fuel consumption and engine performance

Question 30

What does the manifold gauge indicate and how is it calibrated?

Answer 30

It measures the absolute pressure in the engine manifold and is calibrated in inches of mercury

Question 31

What directly controls manifold pressure?

Answer 31

Throttle opening and engine rpm

Question 32

During engine operation, where should the propeller control be set when checking the manifold pressure?

Answer 32

Low pitch, high rpm

Question 33

Is the aircraft electrical system required to power a cylinder head temperature gauge?

Answer 33

No. A thermocouple is used as the electrical source

Question 34

What are the possible indications of an oil pressure transmitter or indicator malfunction?

Answer 34

A severe or sudden drop in oil pressure while the oil temperature remains normal and the oil supply remains full

Question 35

What does a tachometer indicate on a reciprocating engine?

Answer 35

Engine rpm

Question 36

Where should the thermocouple be installed on a reciprocating engine using a single probe cylinder head temperature system?

Answer 36

On the hottest cylinder

Question 37

Explain the main difference and advantage of turbofan engines

Answer 37

A turbofan engine uses a fan to bypass some air around the engine core and to provide thrust. The advantage is that this provides additional thrust without increasing fuel flow

Question 38

Name the major components in a gas turbine engine

Answer 38

Air inlet, compressor section, combustion section, turbine section, exhaust section, gearbox and accessory section

Question 39

What determines the amount of airflow through a turbine engine?

Answer 39

The forward speed of the aircraft, compressor speed, and air density

Question 40

Name the two types of compressors commonly used in turbine engines

Answer 40

Axial and centrifugal flow compressors

Question 41

Name two different methods for attaching turbine engines

Answer 41

Dovetail-type root or bulb type root or fir tree type root

Question 42

what is a split compressor system?

Answer 42

Also called dual or twin spool compressors, these are connected to the turbine section with two rotor shafts, one inside the other

Question 43

What are the different types of combustion chambers used in turbine engines?

Answer 43

Can, annular, can-annular, and reverse flow annular

Question 44

what prevents the combustion chambers from burning?

Answer 44

cooling air along the inside of the liner

Question 45

What is the purpose of the interconnecting tubes attached between can-type combustion chambers?

Answer 45

For flame propagation during start

Question 46

What functions do axial flow turbine nozzles perform?

Answer 46

They direct the mass airflow to drive the turbine rotor at a specific angle

Question 47

How is thermal stress relieved on a turbine disc?

Answer 47

By directing bleed air onto the face of the disk or by grooves being cut in the disk

Question 48

what are carbon seals used for in turbine engines?

Answer 48

They are used as oil seals for the rotor shaft bearings

Question 49

What is shaft horsepower?

Answer 49

It is an indication of the torque developed by a turboprop or turboshaft engine

Question 50

Name the main components of a typical APU

Answer 50

A small power turbine for power and bleed air, and an electrical generator.

Question 51

When is the greatest demand placed on an APU?

Answer 51

When supplying bleed air

Question 52

How is an APU generally started?

Answer 52

With its own electrical starter and battery power

Question 53

Where does the APU get its fuel supply

Answer 53

From one of the aircrafts main fuel tanks

Question 54

At what speed does a gas turbine APU operate and how is this speed maintained?

Answer 54

At or near its rated speed regardless of electrical or pneumatic loads imposed. The APU fuel control automatically adjusts the fuel flow to maintain the rated speed

Question 55

what is used to prevent a heavily loaded APU from exceeding it maximum EGT?

Answer 55

A load control valve modulates the pneumatic load to maintain EGTs within limits

Question 56

How is an APU shut down and why is this procedure used?

Answer 56

After the APU is unloaded by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize. This cool down period is typically three minutes. If a heavily loaded APU is abruptly shut down without any cooling down period, damage could occur as a result of thermal shock

Question 57

What powers the variable inlet guide vanes used on some APUs to regulate the compressor intake airflow?

Answer 57

Fuel Pressure

Question 58

What is fan blade shingling?

Answer 58

It is the overlapping of the midspan shrouds of the fan blade..

Question 59

When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?

Answer 59

Any rubbing sound or other unusual noises from the engine

Question 60

Why are compressor washes performed and what methods are commonly used?

Answer 60

TO remove any contaminants from the compressor section and improve engine performance. The fluid wash and abrasive grit wash are commonly used

Question 61

How can you tell if a turbofan or turbojet engine is out of trim?

Answer 61

There will be a high exhaust gas temperature at the target engine pressure ration for takeoff power.

Question 62

Name the different types of compressor blade damage that may be found during iinspection.

Answer 62

Dents, cracks, galling.. pitting, scratches, burrs, burns, gouges.

Question 63

What kind of markers can be used to mark the parts in hot and cold sections during repair?

Answer 63

Layout dye, delt tip marker, chalk.

Question 64

How does relative humidity affect turbine engines?

Answer 64

Negligible effect

Question 65

What criteria determines replacement of life limited turbine engine components

Answer 65

Cycles, hours, and/or calendar time

Question 66

If turbine blades are removed from a turbine disc, why should they be re-installed in the same location?

Answer 66

To maintain the balance of the turbine wheel

Question 67

How are gas turbine engine tachometers calibrated?

Answer 67

They are calibrated in percent RPM

Question 68

On a turbine engine, what is the engine pressure ratio and what does it indicate?

Answer 68

It is the ratio between the total inlet pressure and total turbine exhaust pressure and us used to indicate the thrust developed by the engine

Question 69

On a turbine engine, what does exhaust gas temperature (EGT) indicate and how is it obtained?

Answer 69

EGT is the average temperature of the turbine discharge gasses and is obtained by thermocouples placed near the turbine exit

Question 70

Can the EGT system on a turbine engine be checked without running the engine?

Answer 70

Yes, by checking the resistance of the thermocouples and circuits

Question 71

Name the three components on the Induction system of a reciprocating engine

Answer 71

The air scoop, carburetor or fuel control, and the intake manifold

Question 72

What could happen if the induction system becomes obstructed?

Answer 72

The engine may not be able to produce its rated power or it may nor run at all. This may also be an indication of a dirty air inlet filter

Question 73

How does induction icing affect engine performance

Answer 73

It causes a reduction in power and possible erratic operation

Question 74

How is induction icing categorized

Answer 74

As impact ice, fuel evaporation ice, and throttle ice

Question 75

What is the common method used to prevent induction system ice in a reciprocating engine?

Answer 75

Raise the temperature of induction air with a preheater

Question 76

What causes fuel evaporation ice?

Answer 76

Fuel evaporation ice is formed because of the decrease in air temperature resulting from evaporation of the fuel after it is introduced into the air stream