100+ Free SACAA CPL Aircraft General Knowledge Practice Questions

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Sample SACAA CPL Aircraft General Knowledge Practice Questions

Try these sample questions to test your SACAA CPL Aircraft General Knowledge exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the correct operational sequence of strokes in a four-stroke internal combustion aircraft piston engine?

A.Induction, Compression, Power, Exhaust

B.Induction, Power, Compression, Exhaust

C.Compression, Induction, Power, Exhaust

D.Power, Induction, Compression, Exhaust

Explanation: The standard four-stroke Otto cycle follows the precise order of Induction (intake of air-fuel mixture), Compression (compressing the mixture), Power (combustion driving the piston down), and Exhaust (expelling combusted gases). This cycle requires two full crankshaft revolutions (720 degrees) to complete all four strokes for each cylinder.

2Why are certified aero piston engines equipped with dual magneto ignition systems?

A.To provide safety redundancy and improve combustion efficiency through dual spark plugs

B.To generate direct current electricity for cockpit avionics and flight instruments

C.To allow automatic switching between high-octane and low-octane aviation gasoline

D.To drive the hydraulic pump in the event of an engine-driven alternator failure

Explanation: Dual ignition systems utilize two independent engine-driven magnetos feeding two separate spark plugs per cylinder. This provides essential safety redundancy if one magneto fails in flight while improving fuel combustion efficiency and engine power output.

3What is the primary operational hazard if a magneto ground wire (P-lead) becomes disconnected or broken?

A.The affected magneto remains live ('hot') and can fire the spark plugs if the propeller is moved even with the ignition switch OFF

B.The engine will immediately shut down during the pre-flight magneto check

C.The alternator will trip off the electrical bus due to high reverse voltage spikes

D.The engine cylinder head temperature will immediately exceed redline limits during taxi

Explanation: A magneto is turned OFF by grounding its primary circuit through the P-lead. If the P-lead breaks or disconnects, the primary circuit cannot be grounded, leaving the magneto live ('hot') regardless of ignition switch position.

4Which operating condition is most conducive to spark plug lead fouling in aircraft piston engines?

A.Extended ground idling at low RPM with an overly rich mixture

B.Cruising at high altitude with a lean-of-peak mixture setting

C.High power climb at full throttle with cowl flaps fully open

D.Descent at high airspeed with low manifold pressure and high RPM

Explanation: Extended ground idling at low cylinder head temperatures with a rich mixture prevents tetraethyl lead additives in AVGAS from vaporizing completely. Lead bromide deposits form on spark plug electrodes, causing electrical shorting and engine roughness.

5How does detonation differ from pre-ignition in a four-stroke aircraft piston engine?

A.Detonation is uncoordinated explosive combustion of remaining fuel charge, whereas pre-ignition occurs when the mixture ignites before the normal spark

B.Detonation is caused solely by cold engine oil, whereas pre-ignition is caused by excessive propeller blade pitch

C.Detonation causes an immediate drop in CHT, whereas pre-ignition causes CHT to remain unchanged

D.Detonation only occurs in diesel engines, whereas pre-ignition only occurs in gas turbine engine combustion chambers

Explanation: Detonation is the instantaneous, explosive combustion of unburned end-gas after normal spark ignition, causing extreme pressure spikes. Pre-ignition occurs when hot spots (e.g., glowing carbon deposits) ignite the air-fuel mixture prior to the timed spark discharge.

6During engine mixture leaning in cruise flight, how do Cylinder Head Temperature (CHT) and Exhaust Gas Temperature (EGT) respond as fuel flow is reduced past peak EGT?

A.Both EGT and CHT decrease as mixture becomes leaner than peak EGT (lean-of-peak)

B.EGT increases continuously while CHT drops to zero

C.EGT decreases while CHT increases to redline limits

D.Both EGT and CHT increase continuously until lean die-out occurs

Explanation: Leaning from rich-of-peak increases EGT until peak EGT is reached. Continuing to lean further (lean-of-peak) lowers fuel burn, reducing total heat energy release; consequently, both EGT and CHT decrease beyond peak EGT.

7What is the primary function of cowl flaps on high-performance air-cooled piston aircraft?

A.To regulate cooling airflow through the engine compartment to control cylinder head temperatures

B.To increase wing lift coefficient during short-field takeoffs

C.To bleed high-pressure air into the cabin pressurization system

D.To redirect exhaust gas flow into the turbocharger turbine housing

Explanation: Cowl flaps control the exit area for cooling air flowing past engine cylinder cooling fins. Opening cowl flaps increases airflow pressure differential, enhancing cooling during high-power climbs; closing them reduces aerodynamic drag in high-speed cruise.

8What condition causes fuel vapor lock in aircraft fuel supply lines, and how is it prevented?

A.High fuel temperature and low atmospheric pressure cause volatile fuel components to vaporize; prevented by boost pumps pushing fuel under pressure

B.Low fuel temperature causes water ice to block fuel filters; prevented by adding isopropyl alcohol

C.High fuel density blocks engine fuel nozzles; prevented by leaning the mixture prior to descent

D.Excessive fuel tank venting allows fuel to overflow; prevented by closing tank cap air vents

Explanation: Vapor lock occurs when high ambient temperatures, low ambient pressure at altitude, or high fuel volatility cause fuel to vaporize in suction lines before reaching the engine pump. Electric boost pumps installed in fuel tanks submerge the line in positive pressure, suppressing vapor formation.

9Which array of vital functions is performed by engine lubricating oil in a reciprocating aircraft engine?

A.Lubrication, cooling, sealing, cleaning, corrosion protection, and hydraulic actuation for constant-speed propellers

B.Electrical insulation, fuel atomization, cabin pressurization, and anti-ice thermal protection

C.Oxygen generation, exhaust gas filtration, cylinder spark timing, and vacuum gyro drive

D.Brake pressure boost, wing flap actuation, cabin air heating, and pitot tube heating

Explanation: Engine oil reduces friction between moving metal parts, carries heat away from pistons/cylinders, seals piston ring gaps, removes contaminants to the oil filter, protects internal components against corrosion, and serves as hydraulic fluid for propeller governors.

10An aircraft piston engine produces 200 brake horsepower (BHP) while burning 12 US gallons of AVGAS per hour. Assuming standard AVGAS weight of 6 lb/gal, calculate the Specific Fuel Consumption (SFC).

A.0.36 lb / BHP-hr

B.0.48 lb / BHP-hr

C.0.24 lb / BHP-hr

D.0.60 lb / BHP-hr

Explanation: Fuel consumption weight per hour = 12 US gal/hr × 6 lb/gal = 72 lb/hr. Specific Fuel Consumption (SFC) = Fuel Flow (lb/hr) ÷ Power (BHP) = 72 lb/hr ÷ 200 BHP = 0.36 lb / BHP-hr.

About the SACAA CPL Aircraft General Knowledge Exam

The SACAA CPL Aircraft Technical & General Knowledge examination is a mandatory theoretical paper for obtaining the Commercial Pilot Licence (Aeroplane) in South Africa. It assesses candidate knowledge of aircraft structures, flight control mechanics, 4-stroke piston engines, light turboprop gas turbine operations, fuel injection and carburetion, supercharging and turbocharging, constant-speed feathering propellers, hydraulic and pneumatic actuation, AC/DC electrical distribution, wheel brakes, retractable landing gear, fire detection and extinguishing systems, and onboard emergency equipment under SACAA CAR/CATS Part 61.

Questions

40 scored questions

Time Limit

120 minutes

Passing Score

75%

Exam Fee

R450 per subject sitting under SACAA Part 187 user fees (South African Civil Aviation Authority (SACAA))

SACAA CPL Aircraft General Knowledge Exam Content Outline

20%

Piston Engines & Ignition Systems

Four-stroke operating cycles, cylinder head temperatures, dual ignition systems, spark plug fouling, detonation, pre-ignition, and engine cooling.

15%

Turboprop Engines & Gas Turbines

Gas turbine principles, compressor types, combustion chambers, free-turbine turboprops, torque, ITT/EGT limits, reverse flow, and beta range.

15%

Propellers & Constant-Speed Governors

Fixed-pitch vs variable-pitch, governor flyweight and pilot valve operation, coarse/fine pitch, feathering, unfeathering accumulators, and synchrophasers.

15%

Airframe Structures & Flight Controls

Monocoque and semi-monocoque airframes, primary flight controls, trim/balance tabs, flaps/slats/spoilers, structural limit load factors, and maneuver envelopes.

20%

Hydraulic, Pneumatic & Fuel Systems

Pascal's law, hydraulic fluids and pumps, accumulator functions, vacuum and pneumatic systems, de-icing boots, fuel injection, carburetion, carb icing, and fuel venting.

15%

Electrical Systems, Instruments & Emergency Equipment

AC and DC electrical generation, alternators, busbars, batteries, circuit breakers, landing gear extension/retraction, wheel brakes, fire detection/extinguishing, and emergency equipment.

How to Pass the SACAA CPL Aircraft General Knowledge Exam

What You Need to Know

Passing score: 75%
Exam length: 40 questions
Time limit: 120 minutes
Exam fee: R450 per subject sitting under SACAA Part 187 user fees

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

SACAA CPL Aircraft General Knowledge Study Tips from Top Performers

1Understand constant-speed propeller governor mechanics: practice trace diagrams of flyweight positions, pilot valve movements, oil pressure flow to/from prop hub, and counterweight/spring forces during overspeed, underspeed, and feathering.

2Master piston engine induction and turbocharging: know the difference between turbochargers (exhaust-driven, wastegate controlled, critical altitude) and superchargers (gear-driven), as well as carb icing formation envelopes.

3Learn turboprop engine operating parameters: understand free-turbine vs fixed-shaft designs, ITT/EGT thermal limits, torque limits, propeller reduction gearboxes, and beta range ground handling.

4Review structural load limits and maneuver envelopes: memorize standard category limit load factors (+3.8g / -1.52g for normal category), maneuvering speed (Va), and stall speed scaling ($V_s = V_{s0} \\sqrt{n}$).

5Study electrical and hydraulic \architecture: know DC alternator vs generator characteristics, split-bus vs cross-feed tie breakers, hydraulic fluid types (e.g. MIL-H-5606 red mineral vs phosphate ester Skydrol), and hydraulic accumulator pre-charge principles.

Frequently Asked Questions

What is the pass mark and time limit for SACAA CPL Aircraft General Knowledge?

The pass mark is 75% under CAR 61.01.10. The computer-based examination consists of 40 multiple-choice questions to be completed in 120 minutes.

What is the exam fee for SACAA CPL theory subjects?

The examination fee is R450 per subject sitting under the SACAA Part 187 user fee schedule (approved ATO test centres may charge additional invigilation or facility fees).

What powerplants and systems \are covered on the CPL AGK exam?

The syllabus covers four-stroke piston engines (fuel injection, carburetors, turbocharging/supercharging, ignition systems), light turboprop engines (free-turbine, ITT/torque limits, beta mode), constant-speed propellers, airframe structures, hydraulics, electrical generation, pneumatic de-icing, and fire protection.

Are mathematical calculations included in the Aircraft General Knowledge paper?

Yes, candidates must be prepared to calculate hydraulic output force (F = P × A), load factors in banked turns, stall speed increases, electrical power/current (P = V × I, V = IR), fuel consumption/endurance, and ISA temperature/pressure altitude density corrections.

How should I structure my preparation for SACAA CPL AGK?

Focus on understanding mechanical relationships rather than rote memory: how governor flyweights react to engine speed, how wastegates regulate turbocharger manifold pressure, hydraulic accumulator charging, alternator bus shedding, and structural limit load factors.

100+ Free SACAA CPL Aircraft General Knowledge Practice Questions

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