TECHGEN-BNC-MODULE7

TECHGEN-BNC-MODULE7

1. The octane rating of a fuel and compression ratio of a piston engine have which of the following relations?

a) the lower the octane rating is, the higher the possible compression ratio is
b) the higher the octane rating is, the higher the possible compression ratio is
c) compression ratio is independent of the octane rating.
d) the higher the octane rating is, the lower the possible compression ratio is.

2. Specific fuel consumption is defined as the:

a) maximum fuel consumption of the aircraft.
b) mass of fuel required to produce unit power for unit time.
c) quantity of fuel required to run the engine for one minute at maximum operating conditions.
d) designed fuel consumption for a given rpm.

3. In which sections of the carburettor would icing most likely occur?

a) venturi and the throttle valve
b) main air bleed and main discharge nozzle
c) float chamber and fuel inlet filter
d) accelerator pump and main metering jet

4. The reading on the oil pressure gauge is the:

a) pressure of the oil on the inlet side of the pressure pump.
b) pressure in the oil tank reservoir.
c) difference between the pressure pump pressure and the scavenge pump pressure.
d) pressure of the oil on the outlet side of the pressure pump.

5. The compression ratio of a piston engine is the ratio of the:

a) diameter of the bore to the piston stroke.
b) area of the piston to the cylinder volume.
c) volume of the cylinder with the piston at bottom dead centre to that with the piston at top dead centre.
d) weight of the air induced to its weight after compression.

6. In addition to the fire hazard introduced, excessive priming should be avoided because:

a) it fouls the spark plugs
b) it washes the lubricant of cylinder walls
c) the gasoline dilutes the oil and necessitates changing oil
d) it drains the carburettor float chamber

7. In a piston engine, turbocharger boost pressure may be monitored by:

a) both a CHT gauge and manifold pressure gauge.
b) both engine rpm readings and a manifold pressure gauge.
c) a cylinder head temperature gauge (CHT), a manifold pressure gauge, and engine rpm readings.
d) a manifold pressure gauge only.

8. An excessively rich mixture can be detected by:

a) white smoke from exhaust.
b) black smoke from exhaust.
c) a long purple flame from exhaust.
d) high cylinder head temperatures

9. The fan in a high by-pass ratio turbo-jet engine produces:

a) the greater part of the thrust.
b) the lesser part of the thrust.
c) half the thrust.
d) none of the thrust.

10. In a gas turbine engine, the maximum gas temperature is attained:

a) within the combustion chamber.
b) in the cooling airflow around the flame tube.
c) at the entry to the exhaust unit.
d) across the turbine.

11. The mixture control for a carburettor achieves its control by:

a) varying the fuel supply to the main discharge tube.
b) varying the air supply to the main discharge tube.
c) altering the depression on the main discharge tube.
d) moving the butterfly valve through a separate linkage to the main throttle control.

12. The diffuser in a centrifugal compressor is a device in which the:

a) velocity rises and pressure falls.
b) pressure rises and velocity falls.
c) velocity, pressure and temperature rise.
d) pressure rises at a constant velocity.

13. Which statement is correct concerning the effect of the application of carburettor heat?

a) The density of the air entering the carburettor is reduced, thus leaning the fuel/air mixture.
b) The density of the air entering the carburettor is reduced, thus enriching the fuel/air mixture.
c) The volume of air entering the carburettor is reduced, thus enriching the fuel/air mixture.
d) The volume of air entering the carburettor is reduced, thus leaning the fuel/air mixture.

14. A piston engine compression ratio is the ratio of the:

a) clearance volume to the swept volume.
b) total volume to the swept volume.
c) total volume to the clearance volume.
d) swept volume to the clearance volume.

15. A "hung start" is the failure of an engine to accelerate to its normal idle speed. It may be caused by:

a) compressor surging.
b) failure of the fuel to ignite in the starting sequence after the engine has been accelerated to the required rpm by the starter.
c) an attempt to ignite the fuel before the engine has been accelerated sufficiently by the starter.
d) the starter cutting out early in the starting sequence before the engine has accelerated to the required rpm for ignition.

16. Vapour lock is:

a) vaporizing of fuel in the carburettor
b) the inability of a fuel to vaporize in the carburettor
c) vaporizing of fuel prior to reaching the carburettor
d) the formation of water vapour in a fuel system

17. On a normally aspirated aero-engine fitted with a fixed pitch propeller:

a) in a descent at a fixed throttle setting manifold pressure will always remain constant.
b) manifold pressure decreases as the aircraft climbs at a fixed throttle setting.
c) the propeller setting is constant at all indicated airspeeds.
d) in level flight, manifold pressure will remain constant when the rpm is increased by opening the throttle.

18. A turbocharger system is normally driven by:

a) an electric motor.
b) the exhaust system.
c) an electrically activated hydraulically powered clutch.
d) an hydraulic motor.

19. A turbocharger consists of a:

a) compressor driving a turbine via a reduction gear.
b) compressor and turbine on individual shafts.
c) turbine driving a compressor via a reduction gear.
d) compressor and turbine mounted on a common shaft.

20. In an engine equipped with a float-type carburettor, the low temperature that causes carburettor ice is normally the result of:

a) compression of air at the carburettor venturi
b) low volatility of aviation fuel
c) vaporization of fuel and expansion of the air in the carburettor
d) freezing temperature of the air entering the carburettor

21. The working cycle of a four-stroke engine is:

a) induction, power, compression, exhaust.
b) compression induction, power, exhaust.
c) induction, compression, power, exhaust.
d) induction, compression, expansion, power.

22. The operating principle of float-type carburettors is based on the:

a) measurement of the fuel flow into the induction system
b) automatic metering of air at the venturi as the aircraft gains altitude
c) increase in air velocity in the throat of a venturi causing an increase in air pressure
d) difference in air pressure at the venturi throat and the air inlet

23. A manifold pressure gauge of a piston engine measures:

a) absolute pressure in intake system near the inlet valve.
b) vacuum in the carburettor.
c) fuel pressure leaving the carburettor.
d) absolute air pressure entering the carburettor.

24. For internal cooling, reciprocating engines are especially dependent on:

a) a properly functioning thermostat
b) a rich fuel/air mixture
c) a lean fuel/air mixture
d) the circulation of lubricating oil

25. The primary reason for a limitation being imposed on the temperature of gas flow is to:

a) prevent damage to the jet pipe from overheating.
b) prevent overheating and subsequent creep of the nozzle guide vanes.
c) ensure that the maximum acceptable temperature within the combustion chamber is not exceeded.
d) ensure that the maximum acceptable temperature at the turbine blades is not exceeded.

26. In a gas turbine engine, compressor blades, which are not rigidly fixed in position when the engine is stationary, take up a rigid position when the engine is running due to:

a) the resultant of aerodynamic and centrifugal forces.
b) blade creep.
c) thermal expansion.
d) oil pressure.

27. In order to get the optimum efficiency of a piston engine, the positions of the intake and exhaust valve at the end of the power stroke are:

a) both valves closed.
b) both valves open.
c) intake valve closed and exhaust valve open.
d) exhaust valve closed and intake valve open.

28. The maximum power output which can be obtained from an engine when it is operated at specified rpm and manifold pressure conditions established as safe for continuous operation is termed:

a) maximum power.
b) rated power.
c) critical power.
d) take-off power.

29. An engine pressure ratio (EPR) gauge reading normally shows the ratio of:

a) jet pipe pressure to compressor inlet pressure.
b) combustion chamber pressure to compressor inlet pressure.
c) jet pipe pressure to combustion chamber pressure.
d) compressor outlet pressure to compressor inlet pressure.

30. For a turbine engine, the term self-sustaining speed relates to the speed at which the engine:

a) is designed to idle after starting.
b) operates most efficiently in the cruise..
c) will enable the generators to supply bus-bar voltage.
d) will run without any external assistance.

31. In a piston engine, the purpose of an altitude mixture control is to:

a) correct for variations in the fuel/air ratio due to decreased air density at altitude.
b) weaken the mixture strength because of reduced exhaust back pressure at altitude.
c) prevent a weak cut when the throttle is opened rapidly at altitude.
d) enrich the mixture strength due to decreased air density at altitude.

32. The primary purpose of a supercharger is to:

a) increase quantity of fuel at metering jet
b) provide leaner mixtures at altitudes below 5000 ft
c) maintain power at altitude
d) provide a richer mixture at high altitudes

33. A reverse thrust door warning light on the flight deck instrument panel illuminates when:

a) the reverser doors are locked.
b) the reverser doors have moved to the reverse thrust position.
c) the reverser doors are unlocked.
d) reverse has been selected but the doors have remained locked.

34. Prolonged running at low rpm can have an adverse effect on the functioning of the:

a) fuel filter.
b) sparking plugs.
c) oil pump.
d) carburettor.

35. In a free turbine engine:

a) its shaft may be connected to either a compressor or another turbine.
b) the air enters the compressor via the input turbine.
c) there is no mechanical connection between the compressor and the power output shaft.
d) the compressor and power output shaft are mechanically connected.

36. The purpose of the venturi in a carburettor is to:

a) ensure complete atomisation of the fuel before entering the injection system.
b) create a rise in pressure at the throat before the mixture enters the induction system.
c) create the suction necessary to cause fuel to flow through the carburettor jets.
d) prevent enrichment of the mixture due to high air velocity through the carburettor.

37. At constant fuel flow, if engine compressor air is bled off for engine anti-icing or a similar system, the turbine temperature:

a) may rise or fall depending on which stage of the compressor is used for the bleed and the rpm of the engine at the moment of selection.
b) will fall.
c) will rise.
d) will be unchanged.

38. The main purpose of the mixture control is to:

a) decrease the air supplied to the engine.
b) decrease the oxygen supplied to the engine.
c) adjust the fuel flow to obtain the correct fuel/air ratio.
d) increase the oxygen supplied to the engine.

39. Fuel/air ratio is the ratio between the:

a) mass of fuel and mass of air entering the cylinder.
b) volume of fuel and volume of air entering the cylinder.
c) mass of fuel and mass of air entering the carburettor
d) volume of fuel and volume of air entering the carburettor.

40. When the combustion gases pass through a turbine the:

a) velocity decreases.
b) pressure drops.
c) temperature increases.
d) pressure rises.

41. In a single spool gas turbine engine, the compressor rpm is:

a) greater than turbine rpm.
b) less than turbine rpm.
c) independent of turbine rpm.
d) the same as turbine rpm.

42. The purpose of an ignition switch is to:

a) connect the secondary coil to the distributor
b) control the primary circuit of the magneto
c) connect the contact breaker and condenser in series with the primary coil
d) connect the battery to the magneto

43. Pre-ignition refers to the condition that may arise when:

a) a rich mixture is ignited by the sparking plugs.
b) the sparking plug ignites the mixture too early.
c) the mixture is ignited by abnormal conditions within the cylinder before the spark occurs at the plug
d) the mixture is ignited before the piston has reached top dead centre.

44. The air in a piston engine turbo-supercharger centrifugal compressor:

a) enters at the periphery and leaves via the eye of the impeller.
b) enters via the diffuser and is fed to the impeller at the optimum angle of attack.
c) enters the eye of the impeller and leaves at a tangent to the periphery.
d) enters at a tangent to the rotor and leaves via the stator.

45. Under normal running conditions a magneto draws primary current:

a) from the booster coil.
b) directly from the aircraft batteries.
c) from the aircraft batteries via an inverter.
d) from a self-contained electro-magnetic induction system.

46. A fuel strainer when fitted to a carburettor will be positioned:

a) between the needle valve and the metering jet.
b) downstream of the discharge nozzle.
c) between the metering jet and the discharge nozzle.
d) upstream of the needle valve.

47. The very rapid magnetic field changes (flux) around the primary coil in a magneto are accomplished by the:

a) contact breaker points opening.
b) contact breaker points closing.
c) distributor arm aligning with one of the high tension segments.
d) rotor turning past the position of maximum flux in the armature.

48. The reason for having a low pressure fuel-cooled oil cooler in a recirculatory type oil system is to:

a) heat the fuel only.
b) cool both the oil and the fuel.
c) cool the oil only.
d) cool the oil and heat the fuel.

49. Overheating of a piston engine is likely to result from an excessively:

a) weak mixture.
b) rich mixture.
c) high barometric pressure.
d) low barometric pressure.

50. The purpose of a distributor in an ignition system is to distribute:

a) secondary current to the condenser.
b) primary current to the sparking plugs.
c) primary current to the condenser.
d) secondary current to the sparking plugs.

51. A "fan" stage of a ducted-fan turbine engine is driven by:

a) the high pressure turbine.
b) the high pressure compressor through reduction gearing.
c) the low pressure turbine.
d) airflow drawn across it by the high pressure compressor.

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