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100+ Free ATPL Aircraft General Knowledge Practice Questions

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2026 Statistics

Key Facts: ATPL Aircraft General Knowledge Exam

80

Official Exam Questions

CAASL Personnel Licensing

3 hours

Exam Duration

CAASL Personnel Licensing

75%

Passing Score Requirement

CAASL Personnel Licensing

LKR 4,000

Exam Registration Fee

CAASL Official Fee Schedule

Katunayake

Exam Center Location

CAASL Head Office Center

EASA FCL

Theoretical Syllabus Base

EASA Part-FCL Subject 021/022

The CAASL ATPL Aircraft General Knowledge exam is a 3-hour, 80-question test covering aircraft systems, electrics, powerplants, and instrumentation. It requires a 75% passing score and has a registration fee of LKR 4,000.

Sample ATPL Aircraft General Knowledge Practice Questions

Try these sample questions to test your ATPL 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.

1In a modern multi-engine transport category aircraft, how is the output voltage of a brushless AC generator controlled under varying electrical loads?
A.By varying the excitation current fed into the exciter stator
B.By adjusting the mechanical speed of the generator rotor via the Constant Speed Drive (CSD)
C.By inserting variable resistors in series with the main stator output windings
D.By switching the number of active poles on the main stator winding
Explanation: A brushless AC generator controls its output voltage by adjusting the Direct Current (DC) excitation current supplied to the stator of the exciter generator. When electrical load increases, the voltage regulator increases the exciter stator current, which increases the AC voltage induced in the exciter rotor, rectifying into a higher current in the main generator field, thereby maintaining a constant output voltage.
2An AC generator rated at 115/200 V, 3-phase, 400 Hz is driven by a Constant Speed Drive (CSD). If the engine speed increases from idle to takeoff thrust, what changes occur in the CSD and generator outputs?
A.The CSD output speed increases, increasing both the frequency and the output voltage of the generator
B.The CSD adjusts its internal hydraulic ratio to keep generator speed and frequency constant at 400 Hz, while the voltage regulator keeps voltage constant
C.The generator output frequency increases linearly with engine RPM, but the voltage is regulated to 115 V by the GCU
D.The CSD disconnects the generator at high engine RPMs to prevent overfrequency and overvoltage conditions
Explanation: The Constant Speed Drive (CSD) uses a continuously variable hydraulic pump/motor system to maintain a constant output rotational speed of 12,000 RPM (for a 4-pole generator) to yield a constant 400 Hz frequency, regardless of engine RPM. Meanwhile, the Generator Control Unit (GCU) regulates the excitation current to maintain a constant output voltage of 115/200 V.
3A 6-pole brushless AC generator is installed on an auxiliary power unit (APU). To maintain a constant output frequency of 400 Hz, what must be the rotational speed of the generator rotor?
A.12,000 RPM
B.8,000 RPM
C.6,000 RPM
D.24,000 RPM
Explanation: Using the formula f = (N * P) / 120, where f is the frequency (400 Hz) and P is the number of poles (6), we can solve for speed N. Rearranging the formula gives N = (120 * f) / P, which calculates as N = (120 * 400) / 6 = 48,000 / 6 = 8,000 RPM.
4What is the primary danger associated with overcharging a Nickel-Cadmium (Ni-Cd) aircraft battery, and how is it characterized?
A.Thermal runaway, characterized by a rapid drop in internal resistance and an exponential rise in cell temperature and charging current
B.Sulfation, characterized by the accumulation of lead sulfate crystals on the cell plates, causing capacity loss
C.Electrolyte stratification, where acid separates from water and concentrates at the bottom of the battery container
D.Memory effect, which causes the battery to instantly discharge when it reaches a specific state of charge
Explanation: In a Nickel-Cadmium battery, overcharging can lead to thermal runaway. High current causes cell heating, which reduces the internal resistance of the cells. In a constant-voltage charging system, this drop in resistance allows even more current to flow, causing further heating in a self-sustaining cycle that can lead to boiling of the electrolyte and fire.
5What is the primary function of a Transformer Rectifier Unit (TRU) in an aircraft electrical system?
A.To convert 28 V DC power to 115 V AC power
B.To step down 115 V AC power and convert it to 28 V DC power
C.To convert variable frequency AC power to constant frequency AC power
D.To step up 28 V DC power to 115 V DC power
Explanation: A Transformer Rectifier Unit (TRU) is a static electrical component that converts Alternating Current (AC) to Direct Current (DC). It uses a transformer to step down 115 V AC to approximately 28 V AC, and then passes it through a solid-state diode rectifier to produce 28 V DC power to feed the DC buses.
6What is the primary purpose of a static inverter in an aircraft electrical system?
A.To convert 115 V AC power to 28 V DC power
B.To convert 28 V DC power to 115 V AC power to run essential AC loads during emergency operations
C.To regulate the voltage output of the auxiliary power unit (APU) generator
D.To convert variable frequency AC from the engines to a constant 400 Hz frequency
Explanation: A static inverter is a solid-state electronic device that converts Direct Current (DC) to Alternating Current (AC). In emergency conditions when all AC generators fail, the static inverter draws 28 V DC from the batteries to produce 115 V AC to power essential instruments and equipment on the AC essential bus.
7In a split-bus electrical system, what is the main function of the Bus Tie Contactors (BTCs)?
A.To automatically connect the main AC generators in parallel to share the electrical load
B.To isolate faulted buses and route power from an operational source to an unpowered bus
C.To step down the main AC generator output before routing it to the TRUs
D.To connect the main batteries directly to the AC distribution system
Explanation: In a split-bus system, AC power sources are never connected in parallel. Bus Tie Contactors (BTCs) open and close to route power from any active generator (including the APU or external power) to any main AC bus whose dedicated generator has failed, keeping the buses isolated from each other but still powered.
8Which of the following functions is NOT performed by a typical modern Generator Control Unit (GCU)?
A.Overvoltage and undervoltage protection
B.Automatic synchronization of generator output phase angles
C.Underfrequency and overfrequency protection
D.Excitation current regulation to control voltage
Explanation: Modern aircraft generators operating in a split-bus configuration do not require phase synchronization because they are never connected in parallel. The GCU controls the output voltage via excitation current, protects against voltage and frequency anomalies, and disconnects the generator line contactor if an anomaly occurs, but it does not synchronize phase angles.
9What is a characteristic advantage of a Nickel-Cadmium (Ni-Cd) battery compared to a Lead-Acid battery in transport aircraft?
A.The Ni-Cd battery has a very flat discharge voltage curve, maintaining constant voltage until near exhaustion
B.The Ni-Cd battery is completely immune to thermal runaway and requires no temperature monitoring
C.The Ni-Cd battery electrolyte can be neutralized with baking soda in the event of a spill
D.The Ni-Cd battery has a lower power-to-weight ratio, which provides better electrical stability
Explanation: Nickel-Cadmium batteries have a very low internal resistance and a flat discharge curve, meaning they maintain a relatively constant terminal voltage of about 1.2 V per cell throughout most of their discharge cycle. However, they require careful temperature monitoring because of their susceptibility to thermal runaway.
10To operate two AC generators in parallel, which of the following parameters must be matched?
A.Voltage, frequency, phase angle, and phase sequence
B.Voltage and frequency only
C.KVAR rating and frequency only
D.Armature current, voltage, and phase angle
Explanation: For two AC generators to be safely connected to the same bus in parallel, they must be synchronized. This means their outputs must match in voltage amplitude, frequency, phase angle (real-time alignment of waves), and phase sequence (order in which phases reach peak voltage), otherwise large destructive circulating currents will flow.

About the ATPL Aircraft General Knowledge Exam

The Sri Lanka CAA ATPL(A) Aircraft General Knowledge Examination is a core theoretical exam for candidates pursuing an Airline Transport Pilot License (Aeroplane) in Sri Lanka. Grounded in the EASA Part-FCL syllabus, the examination evaluates a candidate's comprehensive understanding of aircraft construction, systems, powerplants, instruments, and electrical systems. It ensures pilots possess the engineering and technical depth required to safely command large, complex multi-engine transport category aircraft under normal, abnormal, and emergency conditions. The exam is administered by the Civil Aviation Authority of Sri Lanka (CAASL) as a computer-based test at the Katunayake examination center. Candidates face 80 multiple-choice questions testing systems knowledge (DC/AC electrics, hydraulics, flight controls, pneumatics), powerplants (piston, turboprop, and turbofan engines), and instruments (pitot-static, gyroscopic, air data computer, EFIS, FMS). Solid preparation involves studying system schematics, understanding failure modes, and learning emergency checklists.

Assessment

80 multiple-choice questions, 3 hours, 75% passing score, computer-based testing at the CAASL Katunayake exam center

Time Limit

3 hours

Passing Score

75%

Exam Fee

LKR 4,000 (Civil Aviation Authority of Sri Lanka (CAASL) Examination Center)

ATPL Aircraft General Knowledge Exam Content Outline

25%

System Components, Hydraulics & Pneumatics

Hydraulic systems, reservoirs, accumulators, landing gear extension/retraction, anti-skid, carbon brakes, nose-wheel steering, bleed air pneumatics, air conditioning packs, and cabin pressurization control.

25%

DC & AC Electrics

Batteries, DC generators, brushless AC generators, IDGs/CSDs, AC/DC distribution, bus tie contactors, Transformer Rectifier Units (TRUs), static inverters, and emergency electrical power configuration.

25%

Turbine Engines & Powerplants

Compressor design (axial/centrifugal), combustion, turbine section cooling and limits, exhaust, thrust reversers, FADEC systems, engine starting, ignition, fuel systems, and propeller control systems.

25%

Instrumentation & Avionics

Pitot-static instruments (ASI, VSI, Altimeter, Machmeter), Air Data Computers (ADC), gyroscopes, Apparent/Transport wander calculations, Inertial Reference Systems (IRS), EFIS, TCAS, EGPWS, and FMS operations.

How to Pass the ATPL Aircraft General Knowledge Exam

What You Need to Know

  • Passing score: 75%
  • Assessment: 80 multiple-choice questions, 3 hours, 75% passing score, computer-based testing at the CAASL Katunayake exam center
  • Time limit: 3 hours
  • Exam fee: LKR 4,000

Keys to Passing

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

ATPL Aircraft General Knowledge Study Tips from Top Performers

1Prioritize electrical bus logic (CSD/IDG operation, split-bus vs parallel systems) as electrics is a heavily tested and complex area.
2Memorize turbine engine terminology and parameters, specifically the differences between N1 (fan/LP compressor speed), N2 (HP compressor speed), EGT, and EPR.
3Practice gyro apparent drift and transport wander calculations, ensuring you know when to add or subtract rates based on the hemisphere.
4Understand hydraulic components, focusing on the specific functions of accumulators (storing pressure, dampening surges) and hydraulic fuses (isolating leaks).
5Familiarize yourself with altimeter temperature correction calculations: a colder-than-standard atmosphere causes the altimeter to over-read.

Frequently Asked Questions

What is the fee and location for the CAASL ATPL AGK exam?

The examination fee is LKR 4,000 per subject registration. All CAASL computerized theoretical knowledge examinations are conducted in person at the Civil Aviation Authority of Sri Lanka Head Office located in Katunayake, near the Bandaranaike International Airport.

What is the structure and passing score of the actual examination?

The official CAASL ATPL Aircraft General Knowledge (AGK) exam consists of 80 multiple-choice questions. The allowed duration is 3 hours (180 minutes), and you must score a minimum of 75% (at least 60 correct answers) to pass.

What happens if I fail an ATPL theoretical knowledge subject?

If you fail, you can book a retake for a subsequent session by paying the LKR 4,000 fee again. Under EASA rules adopted by CAASL, you must pass all 14 ATPL subjects within 18 months from the end of the calendar month when you first sat for an exam, and you are limited to a maximum of 4 attempts per subject and 6 sittings in total.

How does this practice bank compare to the actual CAASL exam?

This practice bank provides 100 high-quality multiple-choice questions designed to mirror the EASA Part-FCL syllabus used by CAASL. While it serves as an excellent study tool, the actual CAASL exam uses a randomized selection of 80 questions covering the same detailed learning objectives.