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Module 14 Propulsion (B2): 49 practice questions

Real EASA paper: B2 32 Q / 40 min · B2L 32 Q / 40 min. Three options, 75% to pass. Answer key on the last page. From part66exam.com · independent study aid, not an official exam or a past paper.

1. On an EICAS thrust display, the EPR value shown for each engine is computed as the ratio of:
1. A. compressor delivery pressure to fuel pressure
2. B. turbine discharge to compressor inlet total pressure
3. C. engine oil pressure to ambient static pressure
2. An autofeather system:
1. A. feathers the propeller automatically after engine failure
2. B. unfeathers the propeller for an air start
3. C. synchronises the propellers in cruise
3. A propulsion battery pack has 96 cells in series, each 3.6 V nominal, with a capacity of 50 Ah. Its nominal stored energy is about:
1. A. 4.8 kWh
2. B. 172.8 kWh
3. C. 17.3 kWh
4. Magneto timing to the engine is checked using:
1. A. the EGT gauge during engine run
2. B. a timing light and a TDC indicator
3. C. a fuel flow meter at full power
5. A turbine engine oil pressure indication that is 'differential' measures:
1. A. oil pressure relative to cabin pressure
2. B. oil pressure relative to bearing sump pressure
3. C. oil pressure relative to fuel pressure
6. A propeller de-icing timer cycles power:
1. A. between blades or sections, in sequence
2. B. continuously to all blades at once
3. C. only when the aircraft is on the ground
7. When autothrust is engaged on a FADEC-equipped aircraft, the autothrust function:
1. A. bypasses the EEC and drives the metering valve directly
2. B. disables the EEC's overspeed and N1 limit protection
3. C. sends commands to the EEC, which still applies engine limits
8. The energy stored in a high-energy ignition unit is measured in:
1. A. volts
2. B. amperes
3. C. joules
9. On a turboprop with an ITT indication, the thermocouple probes are located:
1. A. between the HP and LP turbines
2. B. at the compressor inlet guide vanes
3. C. in the oil tank return line
10. Propeller speed (Np) on a turboprop is usually indicated using:
1. A. a thermocouple mounted in the propeller hub
2. B. the torquemeter oil pressure transmitter
3. C. a speed pickup on the reduction gearbox
11. Once the engine is running, many FADECs are powered mainly by:
1. A. the aircraft main battery through the hot bus
2. B. a dedicated engine-driven permanent magnet alternator
3. C. the APU generator through a dedicated relay
12. Spark plug leads on a piston engine that show chafed insulation must be:
1. A. wrapped with fabric tape
2. B. repaired or replaced
3. C. ignored while the engine runs smoothly
13. The output of an EGT system on a FADEC engine is used by the EEC for:
1. A. controlling the propeller governor
2. B. setting cabin pressure
3. C. limiting fuel flow to protect the turbine
14. Propeller synchronising on a twin-engine aircraft is intended to:
1. A. make both propellers turn in opposite directions
2. B. keep both propellers at the same RPM
3. C. keep the blades at a fixed angle
15. The nozzle guide vanes ahead of a turbine rotor:
1. A. slow the gas to raise its pressure
2. B. accelerate the gas and direct it onto the blades
3. C. hold the combustion chamber in position
16. Oil temperature on many engines is measured with:
1. A. a resistance bulb with a bridge or ratiometer
2. B. a thermocouple in the exhaust duct
3. C. a tacho generator on the oil pump
17. Heater current for the blades of an electrically de-iced propeller reaches the rotating hub by way of:
1. A. a brush block and slip rings
2. B. a rotary hydraulic union
3. C. an inductive coil on the spinner
18. A FADEC normally has two channels so that:
1. A. if one channel fails the other controls the engine
2. B. each channel can control a different engine
3. C. one channel controls fuel and one controls oil
19. A piston engine EGT probe is mounted in the exhaust stack close to the cylinder so that it can be used for:
1. A. accurate mixture leaning
2. B. measuring the oil temperature
3. C. setting the magneto timing
20. Beta mode on a turboprop refers to:
1. A. governing at constant speed in flight
2. B. propeller feathering after engine failure
3. C. direct blade angle control on the ground
21. In a hydromechanical fuel control unit, fuel flow is scheduled using:
1. A. software running in a digital computer
2. B. mechanical sensing of speed, pressure and lever
3. C. signals from the fuel quantity indication
22. A capacitance-type oil quantity probe is affected by oil temperature because:
1. A. dielectric constant and volume change with temperature
2. B. the probe melts at normal oil temperatures
3. C. hot oil becomes a good electrical conductor
23. A propeller electronic control fault may cause the system to revert to:
1. A. immediate feather in all cases
2. B. engine shutdown
3. C. a hydromechanical governor backup
24. The APU starter motor must not be operated beyond its duty cycle because it can:
1. A. drain the fuel tanks
2. B. over-pressurise the cabin
3. C. overheat
25. An 'engine monitoring unit' in a light aircraft typically records:
1. A. the cockpit voice and intercom audio
2. B. engine parameters for later analysis
3. C. navigation waypoints and track only
26. A synchrophaser obtains blade position information from:
1. A. the aircraft air data computers
2. B. the engine fuel flow transmitters
3. C. pulse generators on each propeller
27. Before working on the high-voltage system of an electric aircraft, the technician must:
1. A. switch off only the avionics master switch
2. B. remove the propeller from the motor shaft
3. C. isolate, lock out and verify zero voltage
28. A type K thermocouple produces roughly 41 microvolts per degree Celsius. For a 600 C difference between junctions, the EMF is about:
1. A. 2.46 mV
2. B. 246 mV
3. C. 24.6 mV
29. Fuel injection on piston aero engines gives:
1. A. better fuel distribution and less induction icing
2. B. simpler construction than a float carburettor
3. C. no need for a fuel pump of any kind
30. If a resistance bulb circuit goes open circuit, a Wheatstone bridge indicator usually reads:
1. A. exactly zero
2. B. the correct value
3. C. full scale high
31. In a parallel hybrid propulsion system:
1. A. the engine only charges the battery through a generator
2. B. the motor is used only to start the engine
3. C. engine and electric motor can both drive the propeller shaft
32. Engine speed on a turbine engine is usually displayed as:
1. A. revolutions per second of the shaft
2. B. a percentage of a reference RPM
3. C. kilometres per hour of blade tip speed
33. The emergency battery disconnect of an electric aircraft is used to:
1. A. isolate the HV battery in a fire or crash
2. B. increase motor torque for a go-around
3. C. start the range-extender engine
34. A manifold pressure gauge that reads ambient pressure with the engine running at high power suggests:
1. A. a leak or disconnected line in the MP system
2. B. normal operation of the turbocharger
3. C. an overcharged battery affecting the gauge
35. A lithium battery fire is difficult to extinguish because:
1. A. water always makes the fire much hotter
2. B. the fire needs no fuel to keep burning
3. C. the cells keep generating heat and flammable gas
36. In a gas turbine engine, combustion takes place at approximately constant:
1. A. pressure
2. B. volume
3. C. temperature
37. Variable stator vanes in a turbofan compressor are scheduled by:
1. A. the EEC via fuel-powered actuators
2. B. the pilot through a cockpit lever
3. C. centrifugal flyweights on the fan
38. The combustion section of a gas turbine engine is where:
1. A. air is compressed in a series of stages
2. B. the propeller blade pitch is controlled
3. C. fuel burns continuously at almost constant pressure
39. The EEC alternates the active channel on successive starts so that:
1. A. both channels are exercised and latent faults found
2. B. fuel consumption during start is reduced
3. C. one channel can later be removed
40. Turbine blade 'creep' is a permanent lengthening caused by:
1. A. operation at low temperature for long periods
2. B. high temperature and centrifugal stress over time
3. C. rapid changes in propeller blade pitch
41. A float carburettor meters fuel by:
1. A. direct injection into each cylinder
2. B. compressing the mixture in the float bowl
3. C. the pressure drop in a venturi
42. Built-in test equipment (BITE) in a FADEC:
1. A. detects and records faults for maintenance
2. B. increases take-off thrust when required
3. C. controls the cabin temperature schedule
43. If both FADEC channels fail, the engine will typically:
1. A. accelerate to maximum thrust automatically
2. B. go to its designed fail-safe state
3. C. hold the last setting for the rest of the flight
44. The EEC receives altitude, Mach number and total air temperature from:
1. A. the fuel quantity indicating system
2. B. the cabin pressure controller
3. C. the air data computers and its own sensors
45. A supervisory electronic engine control differs from a FADEC in that:
1. A. it only trims a hydromechanical unit, which remains as backup
2. B. it has full authority over the engine with no backup at all
3. C. it controls only the cabin air and pressurisation systems
46. The diffuser between the compressor and the combustor of a turbine engine:
1. A. speeds up the air and lowers its pressure
2. B. slows the air and raises its static pressure
3. C. mixes the fuel into the compressed air
47. The APU load control (bleed) valve is kept closed during:
1. A. APU start and acceleration
2. B. full electrical and bleed load operation
3. C. main engine start using APU air
48. In a gas turbine engine, the main job of the turbine is to:
1. A. compress the air before it enters the combustion section
2. B. extract energy from the gas to drive the compressor and accessories
3. C. mix the fuel with the air before ignition takes place
49. A pack of 100 cells in series, each 3.6 V nominal, has a nominal voltage of:
1. A. 3.6 V
2. B. 36 V
3. C. 360 V

Answer key

1. B — EPR = Pt7/Pt2 (or similar stations); it is proportional to thrust and is used as a thrust-setting parameter.
2. A — When armed, a loss of engine torque triggers automatic feathering to reduce drag.
3. C — Pack voltage = 96 x 3.6 = 345.6 V. Energy = V x Ah = 345.6 x 50 = 17 280 Wh = 17.3 kWh.
4. B — The magneto is set to fire at the correct crankshaft angle before TDC.
5. B — Differential oil pressure excludes the effect of sump pressurisation, showing the pressure actually delivered to the bearings.
6. A — Cycling heats sections in sequence, reducing electrical load and allowing ice to be thrown off.
7. C — Autothrust computes the thrust target and sends it to the EEC (as a thrust lever/N1 command). The EEC continues to control fuel flow and to enforce limits such as N1/N2 and EGT protection.
8. C — Units are rated in joules (e.g. 12 or 20 J).
9. A — ITT probes sit between turbine stages where temperatures are more uniform and closer to the critical turbine inlet temperature.
10. C — A speed sensor on the reduction gearbox or propeller shaft gives a frequency proportional to propeller RPM.
11. B — A dedicated PMA gives an independent supply; aircraft power is used for starting and as a backup.
12. B — Damaged insulation can cause misfire, radio noise and arcing.
13. C — The EEC uses EGT to limit fuel during start and operation.
14. B — Synchronising adjusts the slave engine's governor so its RPM matches the master, eliminating the 'beat' noise.
15. B — The convergent passages of the NGVs increase gas velocity and set the correct angle of attack onto the turbine blades.
16. A — A resistance temperature bulb changes resistance with temperature; a Wheatstone bridge or ratiometer indicator converts this to a reading.
17. A — Brushes on the engine run on slip rings on the propeller backplate, feeding the blade heater elements.
18. A — Dual-channel redundancy (A and B) allows automatic changeover if the active channel fails.
19. A — EGT rises as the mixture is leaned towards peak; the pilot uses the EGT indication to set a mixture a specified amount rich or lean of peak.
20. C — In beta the power lever controls blade angle directly for taxi and reverse.
21. B — Flyweights, bellows and cams in the FCU compute fuel flow mechanically; a supervisory EEC may trim it.
22. A — Compensation is required for accurate indication.
23. C — Many systems have a mechanical governor that takes over on electronic failure.
24. C — Starter motors have limited duty cycles (on/off times); excessive cranking causes overheating and damage.
25. B — Data can be downloaded to detect trends and exceedances.
26. C — Pulses from each hub or shaft are compared to find phase and speed differences.
27. C — HV systems can be lethal: isolation, lock-out/tag-out, waiting for capacitors to discharge and proving absence of voltage are required.
28. C — EMF = 41 uV/C x 600 C = 24 600 uV = 24.6 mV (approximate, since the characteristic is not perfectly linear).
29. A — Fuel is injected at each intake port, giving even distribution and eliminating venturi (carburettor) icing.
30. C — An open bulb appears as infinite resistance, driving the bridge indicator to maximum (off-scale high).
31. C — A parallel hybrid mechanically sums engine and motor power, for example using electric boost for take-off.
32. B — N1 and N2 are shown in percent RPM, 100 percent being a reference speed; this makes different engines easier to compare.
33. A — The disconnect opens the main contactors, removing high voltage from the aircraft systems.
34. A — A leak lets the gauge see ambient pressure rather than manifold pressure.
35. C — Thermal runaway releases heat and gases from the cell chemistry; prolonged cooling is needed and re-ignition is common.
36. A — The Brayton cycle has compression, combustion at nearly constant pressure, expansion and exhaust. A piston engine's Otto cycle burns at approximately constant volume.
37. A — The EEC commands variable geometry to maintain surge margin across the speed range.
38. C — Fuel sprayed from the nozzles burns continuously with part of the compressor air; the remaining air cools the liner and dilutes the gases before the turbine.
39. A — Alternating proves both channels serviceable and reveals hidden faults.
40. B — At high temperatures and stress, metal slowly deforms; turbine blades therefore have temperature limits and life limits, and EGT is closely monitored.
41. C — Airflow through the venturi creates a low pressure that draws fuel from the discharge nozzle in proportion to airflow.
42. A — BITE continuously monitors sensors, actuators and the EEC itself and stores fault codes.
43. B — Each design defines a fail-safe condition, for example a fixed fuel flow or controlled shutdown.
44. C — Air data is used to compute thrust ratings and limits.
45. A — Supervisory EECs fine-tune an FCU; if the EEC fails, the hydromechanical unit still controls the engine.
46. B — The divergent diffuser reduces air velocity so that a stable flame can be maintained, converting kinetic energy into pressure.
47. A — Keeping bleed closed during start lets the APU accelerate without load and reduces the risk of a hot start.
48. B — The turbine converts part of the energy of the combustion gases into shaft power to drive the compressor, the fan or propeller and the accessory gearbox.
49. C — Series connection adds cell voltages: 100 x 3.6 V = 360 V. Parallel connection adds capacity instead.

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