Powerplant Practice

Question 1

What are some advantages of a horizontally opposed engine? (AM.III.A.K4)

Answer 1

Low power-to-weight ratio, ideal for installation on aircraft wings, and low vibration characteristics.

Question 2

How can you determine the firing order of an 18-cylinder radial engine? (AM.III.A.K5)

Answer 2

Begin with cylinder 1, and add 11 or subtract 7, whichever will keep the numbers between 1 and 18. 1-12-5-16-9-2-13-6-17-10-3-14-7-18-11-4-15-8.

Question 3

What is the formula for calculating indicated horsepower on a 4-stroke engine? (AM.III.A.K7)

Answer 3

Indicated horsepower = (PLANK)/33,000

Where:
P = Indicated mean effective pressure, in psi
L = Length of the stroke, in feet or in fractions of a foot
A = Area of the piston head or cross-sectional area of the cylinder, in square inches
N = Number of power strokes per minute: RPM/2
K = Number of cylinders

Question 4

What must normally be done to a nose-wheel airplane before removing an engine? (AM.III.A.K8)

Answer 4

The tail of the airplane must be supported.

Question 5

What are two ways of pre-oiling an engine? (AM.III.A.K8)

Answer 5

Before the spark plugs are installed and after the oil tank or sump is filled, turn the engine over with the starter until oil runs out of the fitting to which the oil pressure gauge connects. OR. Use a pre-oiler tank. Air pressure forces oil through all of the passages until some of it flows from the oil pressure gauge fitting.

Question 6

What four types of gas turbine engines are used in aircraft? (AM.III.B.K2)

Answer 6

Turbofan, turboprop, turboshaft, and turbojet.

Question 7

What is meant by trimming a turbine engine? (AM.III.B.K4)

Answer 7

Adjusting the fuel control so the engine develops the correct idle and trim speed RPM.

Question 8

What type of equipment should be used to determine that a turbine engine is performing up to the standards specified by the engine manufacturer? (AM.III.B.K4)

Answer 8

A JetCal analyzer/trimmer has all of the instrumentation and cables to determine the EGT, EPR, and other parameters specified by the engine manufacturer.

Question 9

What is meant by on-condition maintenance of a turbine engine? (AM.III.B.K5)

Answer 9

The monitoring of the engine performance at regular intervals and determining when maintenance is required based on certain operating parameters specified by the engine manufacturer.

Question 10

What checks of a turbine engine are necessary to verify preflight condition? (AM.III.B.K5)

Answer 10

a. Inspect the cowling and all air inlet areas and attachment of the engine to the airframe
b. Inspect the inlet guide vanes and the first stage of the compressor or fan blades.
c. Check for unusual noise when the compressor is rotated.
d. Inspect the rear turbine and exhaust system.
e. Check the quantity of the lubricating oil for the engine and the constant-speed drive unit.
f. Check the ignition system for operation by listening for the sparks.

Question 11

What engine instruments are monitored during the start of a turbine engine? (AM.III.B.K6)

Answer 11

Tachometer (RPM), oil pressure, and internal gas temperatures.

Question 12

What checks are performed after the installation of a turbine engine? (AM.III.B.K6)

Answer 12

After starting and idle speed is obtained, the engine should stabilize, and engine instrument values are monitored. Takeoff thrust is checked by adjusting the throttle to obtain a single, predicted reading on the engine pressure ratio indicator. The manufacturer’s procedures and limitations must be followed during all engine operations. After engine shut down, inspect the engine for fuel and oil leaks and general condition.

Question 13

What are two sources of compressed air from an APU? (AM.III.B.K10)

Answer 13

From bleed air from the APU turbine compressor, or from a load compressor driven by a free turbine in the engine.

Question 14

Where in maintenance information based on the ATA-100 system would you find instructions for inspecting and servicing the engine of an airborne APU? (AM.II.B.K10)

Answer 14

In section 49-20.

Question 15

How is most of the troubleshooting done for a modern APU? (AM.III.B.K10)

Answer 15

By the fault codes generated by the FADEC.

Question 16

What ensure that an APU will not be shut down while it is too hot? (AM.III.B.K10)

Answer 16

The APU fuel control incorporates an automatic time-delay feature that closes the bleed air valve to remove most of the load and reduce the APU temperature before it is shut down.

Question 17

What prevents the APU exceeding its safe operating limits when the bleed air valve is wide open? (AM.III.B.K10)

Answer 17

The FADEC monitors the load and regulates the fuel going to the APU to prevent it from exceeding its safe limits.

Question 18

What adjustments and rigging are accomplished on a turbine engine? (AM.III.B.K11)

Answer 18

The primary rigging on a turbine engine involves the adjustment of power control levers and cables, followed by careful adjustment of the fuel control unit to trim the engine for the correct idle speeds and to obtain maximum thrust.

Question 19

What regulations specify the inspections that must be accomplished on a general aviation aircraft? (AM.III.C.K1)

Answer 19

14 CFR Part 91, Subpart E.

Question 20

Is a manufacturer’s mandatory service bulletin required to be complied with? (AM.III.C.K5)

Answer 20

No, but it is recommended.

Question 21

Which of the following are FAA-approved data: service letters, service bulletins, instructions for continued airworthiness, ADs, or TCDSs? (AM.III.C.K5)

Answer 21

ADs and TCDSs are approved by the FAA.

Question 22

When must ADs be complied with? (AM.III.C.K5)

Answer 22

All ADs that apply to the affected product must be complied with in accordance with the instructions of the AD and in the time frame specified by the AD.

Question 23

What kind of indicator mechanism is used to measure oil pressure? (AM.III.D.K4)

Answer 23

A Bourdon tube.

Question 24

What kind of indicator mechanism is used to measure manifold pressure? (AM.II.D.K4)

Answer 24

A differential bellows.

Question 25

What should a manifold pressure gauge read when the engine is not operating? (AM.III.D.K4)

Answer 25

The existing barometric pressure as indicated on the altimeter barometric scale when the altimeter pointers are set to the surveyed field elevation.

Question 26

What type of fitting is used to connect an oil pressure gauge to the engine? (AM.III.D.K4)

Answer 26

A fitting with a restrictor that smooths out the pulsations and should a break occur in the indicator line, prevents a serious loss of engine oil.

Question 27

What is used to fill the line between a fuel pressure gauge and the fuel metering system? (AM.III.D.K4)

Answer 27

A light oil such as kerosene.

Question 28

What could cause a fuel pressure gauge to fluctuate? (AM.III.D.K4)

Answer 28

The loss of the light oil in the line between the gauge and the engine.

Question 29

What is the range of pressure needed for a fuel pressure gauge used with a float carburetor? (AM.III.D.K4)

Answer 29

Normally from 1 to 25 psi.

Question 30

What are four types of engine fire detection systems? (AM.III.E.K2)

Answer 30

Thermoswitch system, thermocouple system, thermistor-type continuous-loop system, pneumatic-type continuous-loop system.

Question 31

Which type of fire detection system operates on the principle of the rate of temperature rise? (AM.III.E.K2)

Answer 31

The thermocouple system.

Question 32

Why must the reference junction in a thermocouple fire detection system be thermally insulated? (AM.III.E.K2)

Answer 32

This is a rate-of-temperature-rise system. The reference junction must be insulated so its temperature will not rise as quickly as that of the measuring junctions if a fire should occur.

Question 33

How do you check a thermocouple fire detection system for operation? (AM.III.E.K2)

Answer 33

Press the test switch. This heats the test thermocouple enough for it to close the sensitive relay, which in turn closes the slave relay and activates the fire warning light and bell.

Question 34

How is a pneumatic-type continuous-loop fire detection system checked for operation? (AM.III.E.K2)

Answer 34

When the test switch is closed, low-voltage AC flows through the tube that encloses the sensitive element. This current heats the element enough for it to release sufficient gas to activate the alarm switch.

Question 35

What would likely cause a false fire alarm in a thermistor-type continuous-loop system? (AM.III.E.K3)

Answer 35

A kinked or pinched continuous-loop element.

Question 36

If there is a break in a sing-wire continuous-loop fire detector element, and the system tests bad, will it indicate the presence of a fire. (AM.III.E.K3)

Answer 36

Yes, even though it tests bad, it will still indicate the presence of a fire.

Question 37

What maintenance is allowed on a continuous-loop fire detection system? (AM.III.E.K3)

Answer 37

Inspect and replace as needed the continuous-loop element, the controller, and the fire warning bell and/or light.

Question 38

What is used as the rectifier to produce direct current in a DC alternator? (AM.III.F.K2)

Answer 38

Six solid-state diodes.

Question 39

Why is it not necessary to flash the field of a DC alternator after it has been overhauled? (AM.III.F.K2)

Answer 39

An alternator field is excited by battery current and residual voltage is not used to start the alternator producing current.

Question 40

What is straight mineral oil? (AM.III.G.K1)

Answer 40

It is the lubricating oil as obtained by fractional distillation of crude oil. It does not have any additives.

Question 41

What is ashless dispersant (AD) oil? (AM.III.G.K1)

Answer 41

A mineral lubricating oil containing additives that disperse the contaminants throughout the oil so they will not clump and clog oil passages. There are no ash-forming additives in AD oil.

Question 42

What is synthetic oil? (AM.III.G.K1)

Answer 42

A lubricating oil that is made by chemically changing the nature of an oil base to give it the needed characteristics. Synthetic oil is the primary oil for turbine engines.

Question 43

Is automotive oil suitable for use in aircraft engines? (AM.III.G.K1)

Answer 43

No, automotive and aviation oils are formulated for entirely different operating conditions.

Question 44

What is meant by a multiviscosity oil? (AM.III.G.K1)

Answer 44

It is a lubricating oil with a viscosity index improver that increases the viscosity of the oil when it is hot and decreases the viscosity when it is cold.

Question 45

Where can you find the grade of engine oil specified for a particular aircraft? (AM.III.G.K1)

Answer 45

In the airplane flight manual or the pilot's operating handbook for the aircraft.

Question 46

What are six functions of the oil in an aircraft engine? (AM.III.G.K2)

Answer 46

a. Reduces friction b. Seals and cushions c. Removes heat d. Cleans inside the engine e. Protects against corrosion f. Performs hydraulic action

Question 47

What is the purpose of a air-oil separator, or deaerator, in a turbine engine oil tank? (AM.III.G.K2)

Answer 47

In normal operation, the oil picks up a quantity of air and it is swirled as it enters the daerator. The swirling action releases the air from the oil, and the air is used to pressurize the tank.

Question 48

How is oil pressure regulated in an aircraft engine? (AM.III.G.K2)

Answer 48

A pressure-relief valve sense the desired pressure and sends excess oil back into the engine sump.

Question 49

What is the purpose of the restricted orifice in the line between the oil pressure gauge and the engine? (AM.III.G.K2)

Answer 49

The restricted fitting helps dampen any pulsations in the oil pressure caused by the pump.

Question 50

What is a hot-tank lubrication system for a turbojet engine? (AM.III.G.K2)

Answer 50

A lubrication system in which the oil cooler is in the pressure subsystem and the scavenged oil is not cooled before it is returned to the tank.

Question 51

What is a cold-tank lubrication system for a turbojet engine? (AM.III.G.K2)

Answer 51

A lubrication system in which the oil cooler is in the scavenge subsystem, and the scavenged oil is cool before it is returned to the tank.

Question 52

What is the function of the capacitor in a magneto? (AM.III.H.K8)

Answer 52

The capacitor minimizes arcing at the breaker points, and it speeds up the collapse of the primary current as the breaker points open.

Question 53

What happens in a magneto ignition system when the ignition switch is placed in the Off position? (AM.III.H.K8)

Answer 53

The primary circuit is connect to ground.

Question 54

What is checked when a magneto is internally timed? (AM.III.H.K8)

Answer 54

Internally timing a magneto consists of adjusting the breaker points so they will open at the instant the rotating magnet is in its E-gap position, and the distributor rotor is in position to direct the high voltage to cylinder number one.

Question 55

In what position should the ignition switch be placed when using a timing light on the magnetos? (AM.III.H.K8)

Answer 55

In the Both position.

Question 56

What is the E-gap in the magneto timing? (AM.III.H.K8)

Answer 56

The E-gap angle is the position of the rotating magnet where the primary current flowing in the magneto coil is the greatest. The breaker points open when the rotating magnet is in the E-gap position.

Question 57

What adjustment can a mechanic with a Powerplant rating make to a propeller governor?

Answer 57

Adjust the maximum RPM stop.

Question 58

What are the basic steps for removing a typical propeller?

Answer 58

Remove spinner & remove safety wire from mounting bolts. Support prop with a sling and mark the alignment between the prop hub and engine flange. Unscrew mounting nuts, protect threads of studs/bolts as prop is removed. Place on cart for transpo.

Question 59

What controls the blade angle of a prop when operating in the beta range?

Answer 59

Position of power lever.

Question 60

When making a mag check on an engine w/a constant-speed propeller, what position should the propeller be in?

Answer 60

Low-pitch, high RPM position.

Question 61

What is the function of the snap ring inside the hub of a propeller that is mounted on a tapered or splined shaft?

Answer 61

The snap ring allows the prop to be pulled off of the shaft when the retaining nut is backed off.

Question 62

What are the basic types of propellers?

Answer 62

Fixed pitch, ground adjustable, constant-speed non-feathering, and constant-speed feathering.