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100+ Free SAR-66 Module 16 Practice Questions
CAAS SAR-66 AML Module 16 — Piston Engine (MCQ) practice questions are available now; exam metadata is being verified.
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2026 Statistics
Key Facts: SAR-66 Module 16 Exam
72 Q / 90 min
Module 16 Examination (Cat B1.2/B1.4)
CAAS AC 66-13
75%
Pass Mark per Module
SAR-66 Appendix 2
S$87.20
Fee per examination paper (from 1 Jan 2026)
ANO Twelfth Schedule
10 years
Module Pass Validity
SAR-66
3 months
Wait after 2 Fails in 3 Months
SAR-66
10 Subtopics
Syllabus Areas (16.1 to 16.10)
SAR-66 Appendix 1
CAAS SAR-66 Module 16 Piston Engine MCQ is a 72-question, 90-minute examination for Category B1.2 and B1.4 certifying technicians, requiring a 75% pass mark per module under AC 66-13. The exam fee is S$87.20 under the Air Navigation Order Twelfth Schedule (from 1 Jan 2026). The syllabus covers 10 subtopics: 4-stroke/2-stroke operating cycles, engine performance calculations (IHP, BHP, FHP, volumetric efficiency %, compression ratio), mechanical engine construction, float carburetors and continuous-flow fuel injection, magneto ignition and E-gap timing, induction/exhaust/cooling, turbocharging and wastegate control, lubricants and dry/wet sump oil systems, powerplant installation, and engine monitoring/ground operation troubleshooting.
Sample SAR-66 Module 16 Practice Questions
Try these sample questions to test your SAR-66 Module 16 exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1In a 4-stroke aircraft piston engine operating on the Otto cycle, how many crankshaft revolutions occur during one complete 4-stroke cycle per cylinder?
A.Two revolutions (720°)
B.One revolution (360°)
C.Four revolutions (1440°)
D.Half a revolution (180°)
Explanation: A complete 4-stroke cycle (induction, compression, power, exhaust) requires four piston strokes, which corresponds to two full revolutions (720°) of the crankshaft and one revolution (360°) of the camshaft.
2What is 'valve overlap' in an aircraft 4-stroke piston engine, and what benefit does it provide at high RPM?
A.The angular period near Top Dead Center (TDC) when both intake and exhaust valves are open simultaneously, utilizing exhaust gas inertia to draw in fresh intake charge
B.The time when both intake and exhaust valves are completely closed during the power stroke
C.The period when the intake valve is held open during the compression stroke to reduce starter torque
D.The period when exhaust gas flows back into the carburetor
Explanation: Valve overlap occurs at the end of the exhaust stroke and beginning of the intake stroke near TDC when both valves open simultaneously. High-velocity escaping exhaust gas creates a partial vacuum in the cylinder, drawing in the fresh fuel-air charge and scavenging residual exhaust.
3Calculate the Indicated Horsepower (IHP) of a 6-cylinder 4-stroke engine operating with an Indicated Mean Effective Pressure (IMEP) P of 150 psi, stroke length L of 0.25 ft, cylinder bore area A of 20 sq in, and crankshaft speed N of 2400 RPM.
A.163.6 IHP
B.327.3 IHP
C.81.8 IHP
D.654.5 IHP
Explanation: For a 4-stroke engine, power strokes per minute per cylinder = N / 2 = 2400 / 2 = 1200. IHP = (P · L · A · N_power · K) / 33000 = (150 · 0.25 · 20 · 1200 · 6) / 33000 = 5,400,000 / 33000 ≈ 163.6 IHP.
4If a piston engine develops an Indicated Horsepower (IHP) of 300 HP and a Brake Horsepower (BHP) of 255 HP, what are its Friction Horsepower (FHP) and Mechanical Efficiency?
A.FHP = 45 HP, Mechanical Efficiency = 85%
B.FHP = 55 HP, Mechanical Efficiency = 80%
C.FHP = 45 HP, Mechanical Efficiency = 75%
D.FHP = 555 HP, Mechanical Efficiency = 95%
Explanation: Friction Horsepower FHP = IHP - BHP = 300 HP - 255 HP = 45 HP. Mechanical Efficiency η_m = (BHP / IHP) · 100% = (255 / 300) · 100% = 0.85 · 100% = 85%.
5What is 'detonation' in an aircraft piston engine, and what causes it?
A.Uncontrolled, instantaneous explosive burning of the unburned fuel-air mixture ('end gas') caused by excessively high cylinder temperature and pressure
B.Ignition of the fuel-air mixture prior to the timed spark plug discharge
C.Slow, incomplete burning of fuel inside the exhaust muffler
D.Failure of the spark plug to fire on one cylinder
Explanation: Detonation is the spontaneous, explosive auto-ignition of the unburned fuel-air mixture ahead of the flame front. It is caused by low octane fuel, excessive manifold pressure, high CHT, or overly lean mixture, leading to destructive pressure spikes and piston damage.
6How does pre-ignition differ from detonation in a piston engine cylinder?
A.Pre-ignition occurs when the fuel-air mixture is ignited by a localized hot spot (e.g., glowing carbon deposit) before normal spark plug firing
B.Pre-ignition occurs after the piston passes BDC on the exhaust stroke
C.Pre-ignition can only occur when using 100LL fuel in a diesel engine
D.Pre-ignition causes an immediate drop in cylinder head temperature
Explanation: Pre-ignition is caused by a hot spot (glowing carbon deposit, cracked ceramic, or overheated valve) igniting the mixture prematurely before the timed spark. It leads to severe peak pressure before TDC, causing rapid engine damage.
7What is the purpose of pendulum dynamic dampers attached to aircraft engine crankshaft counterweights?
A.To suppress torsional vibrations induced by power impulses at specific engine operating speeds
B.To increase the stroke length of the pistons
C.To splash oil onto the camshaft lobes
D.To lock the crankshaft during starter engagement
Explanation: Dynamic dampers are pendulum counterweights mounted on crank cheeks that oscillate out of phase with power stroke torque fluctuations. This dampens destructive torsional vibration frequencies, protecting the crankshaft from fatigue failure.
8What are the two primary types of piston rings installed on aircraft engine pistons?
A.Compression rings (top) and oil control/wiper rings (bottom)
B.Retaining snap rings and rubber O-rings
C.Ceramic sealing rings and brass scraper rings
D.Helical spring rings and friction lock rings
Explanation: Piston grooves hold compression rings (top grooves) to seal high combustion pressure inside the combustion chamber, and oil control/wiper rings (bottom grooves) to scrape excess oil from cylinder walls back into the crankcase.
9Why are exhaust valve stems in high-output aircraft engines often hollowed out and partially filled with metallic sodium?
A.Sodium melts at operating temperature (~98 °C) and sloshes inside the stem, transferring heat rapidly from the valve head to the guide and cylinder cooling fins
B.Sodium reacts with fuel to increase exhaust gas velocity
C.Sodium makes the valve stem lightweight so it moves at twice the camshaft speed
D.Sodium acts as a dry lubricant for the rocker arm face
Explanation: Liquid sodium sloshes back and forth inside the hollow stem during valve movement, transferring extreme heat away from the hot valve head (> 700 ° C) to the cooled valve guide in the cylinder head.
10What main component controls the fuel level inside the float chamber of a float-type aircraft carburetor?
A.A brass or composite float acting on a needle valve at the fuel inlet seat
B.A high-pressure electric fuel pump bypass valve
C.The mixture control needle in the discharge nozzle
D.The throttle butterfly valve shaft
Explanation: The float rises with fuel level, pressing a needle valve into its seat to stop fuel entry when the correct fuel height is reached, maintaining a constant fuel head relative to the main discharge nozzle.
About the SAR-66 Module 16 Practice Questions
Verified exam format metadata for CAAS SAR-66 AML Module 16 — Piston Engine (MCQ) is pending. The practice questions above remain available while official exam length, timing, passing score, fee, and administrator details are reviewed.