Free CAAS SAR-66 M16 Piston Engine (Category B1.2) Practice Questions

Sample Practice Questions

Try these 10 sample questions from the CAAS SAR-66 M16 Piston Engine (Category B1.2) practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1Which ratio defines the mechanical efficiency of a reciprocating engine?

   1. A.Friction horsepower divided by indicated horsepower
   2. B.Brake horsepower divided by indicated horsepowerCorrect answer: B
   3. C.Indicated horsepower divided by brake horsepower
   4. D.Friction horsepower divided by brake horsepower

   Explanation: The FAA states, "Mechanical efficiency is the ratio that shows how much of the power developed by the expanding gases in the cylinder is actually delivered to the output shaft." Thus it is brake horsepower divided by indicated horsepower. Friction-to-power ratios describe losses; reversing bhp/ihp gives the reciprocal of efficiency.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 1, Mechanical Efficiency

2. 2A test engine delivers 100 lb-ft of shaft torque at 3,000 rpm. Using bhp = 2π × torque × rpm / 33,000, what is its brake horsepower, to one decimal place?

   1. A.9.1 bhp
   2. B.28.6 bhp
   3. C.57.1 bhpCorrect answer: C
   4. D.114.2 bhp

   Explanation: The FAA states, "If the work is expressed in ft-lb per minute, this quantity is divided by 33,000." Work per revolution is 2π × torque. Thus bhp = 2π × 100 lb-ft × 3,000/min ÷ 33,000 = 57.1199, or 57.1 bhp. 9.1 omits 2π; 28.6 omits the factor 2; 114.2 doubles the correct result.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 1, Brake Horsepower—shaft-power calculation

3. 3What happens to airflow velocity and static pressure as air passes through a carburettor venturi throat?

   1. A.Velocity decreases and pressure increases
   2. B.Velocity and pressure both increase
   3. C.Velocity and pressure both decrease
   4. D.Velocity increases and pressure decreasesCorrect answer: D

   Explanation: The FAA states, "As the velocity of the air increases to get through the narrow portion, its pressure drops." The venturi throat accelerates the air and lowers its static pressure. Reversing either change, or making pressure and velocity rise together, misapplies the venturi principle.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 2, Carburetion Principles—Venturi Principles

4. 4Once a conventional magneto-ignition piston engine is rotating, how does its magneto obtain the energy needed to generate ignition voltage?

   1. A.It draws ignition energy continuously from the aircraft battery
   2. B.Engine rotation moves a permanent magnet relative to coil windingsCorrect answer: B
   3. C.It draws ignition energy continuously from the aircraft alternator
   4. D.Residual magnetism supplies ignition energy without mechanical input

   Explanation: The handbook states, "the engine rotating the permanent magnet and inducing a current to flow in the coil windings." A: This confuses a self-generating magneto with battery ignition. B: The source describes mechanical rotation inducing current in the windings. C: The magneto's energy is not supplied continuously by the aircraft alternator. D: A magnetic field without mechanical input is not a continuing energy source.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 4, Magneto-Ignition System Operating Principles

5. 5What is the purpose of the balance tube joining the two runners of the updraft induction system described in the handbook?

   1. A.To maintain a pressure difference between the two induction runners
   2. B.To meter equal fuel flow from a separate jet into each runner
   3. C.To reduce pressure differences between the two induction runnersCorrect answer: C
   4. D.To keep induction pressure isolated between the two engine sides

   Explanation: The handbook states, "The balance tube is used to reduce pressure imbalances between the two side induction runners." A: The tube reduces rather than deliberately maintains imbalance. B: The balance tube is a pressure connection rather than a pair of metering jets. C: The source explicitly states reduced pressure imbalance between runners. D: A connecting balance tube reduces isolation rather than preserving it.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 3, Reciprocating Engine Induction Systems—updraft system

6. 6Which property describes a lubricating oil's resistance to flow?

   1. A.Specific gravity
   2. B.Flash point
   3. C.Dispersancy
   4. D.ViscosityCorrect answer: D

   Explanation: The FAA states, "The resistance of an oil to flow is known as its viscosity." Specific gravity compares density with water, flash point concerns ignitable vapour, and dispersancy concerns suspended particles. None is the name for resistance to flow.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 6, Requirements & Characteristics of Reciprocating Engine Lubricants

7. 7Where is the main oil supply normally stored in a dry-sump piston-engine lubrication system?

   1. A.In the lower crankcase as the main reservoir
   2. B.In the oil-cooler core as the main reservoir
   3. C.In a separate oil tank outside the engine sumpCorrect answer: C
   4. D.In the scavenge-pump housing as the main reservoir

   Explanation: The handbook states, "The dry sump system uses a scavenge pump, some external tubing, and an external tank to store the oil." A: This confuses dry sump with wet-sump crankcase storage. B: The cooler is a heat exchanger rather than the main supply reservoir. C: The source identifies an external tank for dry-sump storage. D: A pump housing transfers oil rather than serving as the main reservoir.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 6, Reciprocating Engine Lubrication Systems—dry sump

8. 8What rotational speed does the conventional reciprocating-engine tachometer indicate?

   1. A.Camshaft revolutions per minute
   2. B.Crankshaft revolutions per minuteCorrect answer: B
   3. C.Magneto-rotor revolutions per minute
   4. D.Starter-armature revolutions per minute

   Explanation: The FAA states, "The tachometer for reciprocating engines shows the engine crankshaft rpm." Other shafts can turn at different ratios to crankshaft speed. Their speeds are not what this engine tachometer is calibrated to indicate.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 10, Tachometer Indicator

9. 9During an established engine ground run, the oil-pressure indication falls to zero. The manufacturer's permitted starting delay is no longer relevant. What action is appropriate?

   1. A.Continue at idle while watching cylinder-head temperature.
   2. B.Shut down the engine and investigate the loss of indication.Correct answer: B
   3. C.Increase engine speed to restore the indicated pressure.
   4. D.Continue the run if the oil-temperature indication is normal.

   Explanation: The handbook states, "The engine should be shut down immediately if the gauge fails to register pressure when the engine is operating." Zero oil-pressure indication during the established run requires shutdown and investigation; normal temperature cannot establish an adequate oil supply, and increasing speed adds exposure to possible oil starvation.

   Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 10, Oil Pressure Indicator

10. 10Why can an inactive piston engine need internal corrosion protection even though it is not accumulating operating hours?

    1. A.Preservative oil supplies the oxygen that makes old deposits corrosive
    2. B.Combustion residues can contain moisture and corrosive by-productsCorrect answer: B
    3. C.Old carbon deposits provide a corrosion barrier removed by preservative
    4. D.Combustion moisture becomes harmless when the engine cools down

    Explanation: The handbook states, "The normal combustion process creates moisture and corrosive by-products that attack the unprotected surfaces". A: The preservation method isolates deposits from moisture and oxygen rather than supplying oxygen. B: The source identifies these residues as attacking unprotected surfaces during inactivity. C: The source describes vulnerable, residue-bearing surfaces needing protection rather than a dependable carbon barrier. D: Cooling does not remove the moisture/residue corrosion risk described for inactive engines.

    Reference: FAA Aviation Maintenance Technician Handbook–Powerplant — Chapter 8, Preservation & Storage of Engines