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GCAA CAR-66 Category A Exam study materials
GCAA CAR-66 Category A Exam study resources

GCAA CAR-66 Category A Exam practice questions

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Question 1Mathematics

A rectangular aircraft panel measures 0.75 m by 1.2 m. What is its area in square metres?

  1. 1.80 m²
  2. 0.90 m² Correct answer.
  3. 0.09 m²
  4. 1.95 m²

Explanation

Area of a rectangle is length multiplied by width: 0.75 × 1.2 = 0.90 m². The units remain square metres because both dimensions are in metres.

Question 2Mathematics

A torque wrench is set to 45 N·m. Convert this value to pound-force feet (lbf·ft), using 1 N·m = 0.7376 lbf·ft.

  1. 45.7 lbf·ft
  2. 27.6 lbf·ft
  3. 33.2 lbf·ft Correct answer.
  4. 61.0 lbf·ft

Explanation

To convert from N·m to lbf·ft, multiply by the conversion factor: 45 × 0.7376 = 33.192, which rounds to 33.2 lbf·ft.

Question 3Mathematics

An aircraft component has a mass of 2.5 kg. What is its weight in newtons, taking the acceleration due to gravity as 9.81 m/s²?

  1. 24.5 N Correct answer.
  2. 98.1 N
  3. 0.255 N
  4. 2.5 N

Explanation

Weight is mass multiplied by gravitational acceleration: W = m × g = 2.5 × 9.81 = 24.525 N, which rounds to 24.5 N.

Question 4Mathematics

A right-angled triangle has a hypotenuse of 13 cm and one leg of 5 cm. What is the length of the other leg?

  1. 144 cm
  2. 18 cm
  3. 12 cm Correct answer.
  4. 8 cm

Explanation

By Pythagoras’ theorem, the square of the hypotenuse equals the sum of the squares of the other two sides: 13² = 5² + b², so b² = 169 − 25 = 144, giving b = 12 cm.

Question 5Mathematics

A batch of 250 rivets contains 15 defective items. What is the percentage of defective rivets?

  1. 16.7%
  2. 6.0% Correct answer.
  3. 0.6%
  4. 15.0%

Explanation

Percentage defect rate is (number defective ÷ total number) × 100: (15 ÷ 250) × 100 = 6.0%.

Question 6Mathematics

An aircraft travels 480 km in 1 hour 20 minutes. What is its average speed in km/h?

  1. 400 km/h
  2. 320 km/h
  3. 360 km/h Correct answer.
  4. 384 km/h

Explanation

Convert the time to hours: 1 h 20 min = 1 + 20/60 = 1.333… h. Average speed = distance ÷ time = 480 ÷ 1.333… = 360 km/h.

Question 7Mathematics

The resistance of a component is given as 4.7 kΩ. Express this value in megohms (MΩ).

  1. 0.0047 MΩ Correct answer.
  2. 470 MΩ
  3. 4.7 MΩ
  4. 0.047 MΩ

Explanation

One kilo-ohm is 10³ Ω and one megohm is 10⁶ Ω, so 1 kΩ = 0.001 MΩ. Therefore 4.7 kΩ = 4.7 × 0.001 = 0.0047 MΩ.

Question 8Mathematics

A cylinder has a radius of 3 cm and a height of 10 cm. Using π ≈ 3.1416, what is its volume?

  1. 94.2 cm³
  2. 188.5 cm³
  3. 565.5 cm³
  4. 282.7 cm³ Correct answer.

Explanation

Volume of a cylinder is V = π r² h. Substituting: 3.1416 × 3² × 10 = 3.1416 × 9 × 10 = 282.744 cm³, which rounds to 282.7 cm³.

Question 9Physics

A mass of 2 kg is accelerated uniformly from rest to 10 m/s in 5 seconds. What is the magnitude of the net force acting on the mass?

  1. 4 N Correct answer.
  2. 2 N
  3. 10 N
  4. 20 N

Explanation

Acceleration is the change in velocity divided by time: (10 - 0)/5 = 2 m/s². Newton's second law gives F = ma = 2 × 2 = 4 N.

Question 10Physics

Which statement correctly describes the relationship between mass and weight?

  1. Mass varies with location, while weight remains constant everywhere.
  2. Mass is a measure of the quantity of matter, while weight is the gravitational force acting on that mass. Correct answer.
  3. Mass and weight are the same quantity expressed in different units.
  4. Weight is a measure of the quantity of matter, while mass is the gravitational force acting on it.

Explanation

Mass is an intrinsic property of a body measured in kilograms and does not change with location. Weight is the force of gravity on that mass (W = mg) and depends on the local gravitational acceleration.

Question 11Physics

A block of density 800 kg/m³ floats in water of density 1000 kg/m³. What fraction of the block's volume is submerged?

  1. 0.2
  2. 1.0
  3. 0.8 Correct answer.
  4. 0.5

Explanation

For a floating body, the submerged fraction equals the ratio of body density to fluid density. Here 800/1000 = 0.8, so 80% of the volume is below the surface.

Question 12Physics

A hydraulic system has a small piston of area 0.01 m² and a large piston of area 0.5 m². If a force of 200 N is applied to the small piston, what force is produced at the large piston (ideal system)?

  1. 4 N
  2. 1 000 N
  3. 10 000 N Correct answer.
  4. 400 N

Explanation

Pascal's principle states pressure is transmitted equally: P = F1/A1 = F2/A2. Thus F2 = F1 × (A2/A1) = 200 × (0.5/0.01) = 10 000 N.

Question 13Physics

A gas is held at constant temperature while its volume is halved. According to Boyle's law, what happens to its pressure?

  1. It is halved.
  2. It is doubled. Correct answer.
  3. It remains unchanged.
  4. It is quadrupled.

Explanation

Boyle's law states that at constant temperature, pressure and volume are inversely proportional (P1V1 = P2V2). Halving the volume therefore doubles the pressure.

Question 14Physics

A body moves in a circular path at constant speed. Which statement about its motion is correct?

  1. It has zero acceleration because its speed is constant.
  2. It accelerates because its velocity direction changes continuously. Correct answer.
  3. It has no net force acting on it because its speed is constant.
  4. Its acceleration is directed along the tangent to the path.

Explanation

Velocity is a vector, so a change of direction is a change of velocity and therefore an acceleration. This centripetal acceleration points toward the centre of the circle and requires a centripetal force.

Question 15Physics

Two resistors of 6 Ω and 3 Ω are connected in parallel. What is the equivalent resistance of the combination?

  1. 4.5 Ω
  2. 2 Ω Correct answer.
  3. 9 Ω
  4. 1.5 Ω

Explanation

For parallel resistors, 1/R = 1/6 + 1/3 = 1/6 + 2/6 = 3/6, so R = 2 Ω. The equivalent resistance is always less than the smallest individual resistance.

Question 16Physics

A body is in static equilibrium under the action of several coplanar forces. Which pair of conditions must both be satisfied?

  1. The sum of the moments about the centre of gravity is zero and all forces act through one point.
  2. The vector sum of the forces is zero and the body is at rest in a vacuum.
  3. The vector sum of the forces is maximum and the moments balance each other.
  4. The vector sum of the forces is zero and the sum of the moments about any point is zero. Correct answer.

Explanation

Static equilibrium requires both translational equilibrium (net force zero) and rotational equilibrium (net moment zero about any point). Satisfying only one condition permits either linear or angular acceleration.

Question 17Electrical Fundamentals

In a purely resistive AC circuit, the current waveform is described as being in phase with the voltage. What does this mean for the phase angle between them?

  1. The phase angle is zero degrees Correct answer.
  2. The phase angle is 90 degrees
  3. The phase angle is 45 degrees
  4. The phase angle is 180 degrees

Explanation

Resistance opposes current without storing energy, so voltage across a resistor and current through it rise and fall together. The phase difference is therefore zero degrees. Phase shifts arise only from reactive components such as inductors or capacitors.

Question 18Electrical Fundamentals

A resistor of 12 ohms carries a current of 0.5 amperes. What is the power dissipated in the resistor?

  1. 3 watts Correct answer.
  2. 24 watts
  3. 6 watts
  4. 12 watts

Explanation

Power in a resistor can be found from P = I squared times R. Squaring 0.5 A gives 0.25, and multiplying by 12 ohms gives 3 watts. The same result follows from P = V times I once the voltage drop of 6 V is calculated.

Question 19Electrical Fundamentals

Which statement correctly describes the magnetic field produced around a straight current-carrying conductor?

  1. It forms concentric circles around the conductor and strengthens with distance
  2. It lies parallel to the conductor and increases with distance
  3. It forms concentric circles around the conductor and weakens with distance Correct answer.
  4. It lies parallel to the conductor and weakens with distance

Explanation

A current produces a magnetic field whose lines encircle the conductor in planes perpendicular to it. The field strength falls as distance from the conductor increases. The direction of the field is given by the right-hand grip rule.

Question 20Electrical Fundamentals

A capacitor of 10 microfarads is charged to 50 volts. How much charge is stored?

  1. 0.5 millicoulombs Correct answer.
  2. 500 microcoulombs
  3. 5 millicoulombs
  4. 50 millicoulombs

Explanation

Charge is given by Q = C times V. Multiplying 10 microfarads by 50 volts gives 500 microcoulombs, which equals 0.5 millicoulombs. Converting units carefully avoids confusing micro and milli prefixes.

Question 21Electrical Fundamentals

Which material property makes a substance suitable for use as a permanent magnet?

  1. Low permeability with low retentivity
  2. Low electrical resistance
  3. High permeability with high retentivity Correct answer.
  4. High electrical resistance

Explanation

A permanent magnet must be easily magnetised and must retain its magnetism once the magnetising force is removed. High permeability allows strong magnetisation, and high retentivity keeps the flux after the field is gone. Hard magnetic materials such as certain steels meet both requirements.

Question 22Electrical Fundamentals

Two resistors of 6 ohms and 3 ohms are connected in parallel. What is the equivalent resistance of the combination?

  1. 0.5 ohms
  2. 2 ohms Correct answer.
  3. 9 ohms
  4. 4.5 ohms

Explanation

For parallel resistors the reciprocals add: 1/R = 1/6 + 1/3 = 1/2. Inverting gives 2 ohms. The equivalent resistance of a parallel network is always less than the smallest individual resistor.

Question 23Electrical Fundamentals

A coil has an inductive reactance of 40 ohms at a particular frequency. If the frequency is doubled while inductance stays constant, what is the new reactance?

  1. 40 ohms
  2. 20 ohms
  3. 80 ohms Correct answer.
  4. 160 ohms

Explanation

Inductive reactance is directly proportional to frequency according to X = 2 pi f L. Doubling the frequency therefore doubles the reactance to 80 ohms. The relationship is linear with respect to frequency.

Question 24Electrical Fundamentals

A transformer has 500 turns on the primary and 50 turns on the secondary. If the primary is supplied at 230 volts, what is the secondary voltage under no load?

  1. 2300 volts
  2. 2.3 volts
  3. 23 volts Correct answer.
  4. 230 volts

Explanation

The voltage ratio equals the turns ratio: Vs/Vp = Ns/Np. The ratio here is 50/500, or one tenth, so the secondary voltage is 23 volts. This is a step-down transformer.

Question 25Electrical Fundamentals

In a three-phase star-connected supply, the line voltage is 400 volts. What is the phase voltage?

  1. 133 volts
  2. 692 volts
  3. 230 volts Correct answer.
  4. 400 volts

Explanation

For a star connection the line voltage is the phase voltage multiplied by the square root of three. Dividing 400 volts by roughly 1.732 gives about 231 volts, conventionally quoted as 230 volts. In a delta connection the line and phase voltages are equal.

Question 26Electrical Fundamentals

Which effect explains why the current in an inductive circuit appears to lag the applied voltage?

  1. The inductor stores energy in an electric field that opposes voltage change
  2. The inductor stores energy in a magnetic field that assists current change
  3. The inductor stores energy in a magnetic field that opposes current change Correct answer.
  4. The inductor dissipates energy as heat that opposes current change

Explanation

An inductor stores energy in a magnetic field, and by Lenz's law the induced emf opposes any change in current. This opposition delays the rise of current, so current lags voltage. The energy is returned to the circuit when the field collapses.

Question 27Electrical Fundamentals

A 12 volt battery is connected to a circuit with a total resistance of 4 ohms. What current flows, and how much charge passes a point in 30 seconds?

  1. 48 A and 1440 coulombs
  2. 3 A and 90 coulombs Correct answer.
  3. 3 A and 360 coulombs
  4. 0.33 A and 10 coulombs

Explanation

Ohm's law gives I = V/R = 12/4 = 3 amperes. Charge is current multiplied by time, so 3 A times 30 s equals 90 coulombs. Both steps use fundamental DC relationships.

Question 28Electrical Fundamentals

A capacitor and a resistor are connected in series across a DC supply. Which statement describes the steady-state condition after the capacitor has fully charged?

  1. Current continues at a constant value and the capacitor voltage is zero
  2. Current is maximum and the capacitor voltage equals the supply voltage
  3. Current is zero and the capacitor voltage equals the supply voltage Correct answer.
  4. Current is zero and the capacitor voltage is zero

Explanation

Once fully charged, the capacitor blocks further direct current, so the current falls to zero. With no current there is no drop across the resistor, so the full supply voltage appears across the capacitor. A capacitor passes current only while its voltage is changing.

Question 29Electrical Fundamentals

A wire of uniform material has a resistance of 8 ohms. If its length is doubled and its cross-sectional area is also doubled, what is the new resistance?

  1. 4 ohms
  2. 8 ohms Correct answer.
  3. 32 ohms
  4. 16 ohms

Explanation

Resistance is proportional to length and inversely proportional to cross-sectional area. Doubling the length doubles the resistance, while doubling the area halves it, so the two effects cancel. The resistance remains 8 ohms.

Question 30Electrical Fundamentals

An AC circuit contains a resistor of 30 ohms and an inductive reactance of 40 ohms in series. What is the impedance?

  1. 70 ohms
  2. 10 ohms
  3. 35 ohms
  4. 50 ohms Correct answer.

Explanation

Impedance in a series R-L circuit is the vector sum given by the square root of R squared plus X squared. That is the square root of 900 plus 1600, which is the square root of 2500, or 50 ohms. Resistance and reactance cannot simply be added arithmetically.

Question 31Electrical Fundamentals

A series circuit has a 6 volt source and two resistors of 2 ohms and 4 ohms. Using Kirchhoff's voltage law, what is the voltage drop across the 4 ohm resistor?

  1. 2 volts
  2. 6 volts
  3. 3 volts
  4. 4 volts Correct answer.

Explanation

The total resistance is 6 ohms, so the current is 1 ampere. The drop across the 4 ohm resistor is therefore 4 volts, and the drop across the 2 ohm resistor is 2 volts, summing to the supply voltage as Kirchhoff's voltage law requires.

Question 32Electrical Fundamentals

A coil of 0.2 henries carries a current that changes at a rate of 50 amperes per second. What emf is induced in the coil?

  1. 10 volts Correct answer.
  2. 0.004 volts
  3. 250 volts
  4. 0.1 volts

Explanation

The self-induced emf equals the inductance multiplied by the rate of change of current, with a sign that opposes the change. Multiplying 0.2 H by 50 A/s gives 10 volts. This is the basis of the inductor's opposition to changing current.

Question 33Electronic Fundamentals

In a forward-biased silicon PN junction diode, the typical voltage drop across the junction is approximately:

  1. 0.7 V Correct answer.
  2. 1.2 V
  3. 5.0 V
  4. 0.3 V

Explanation

A silicon junction requires about 0.7 V of forward bias before it conducts appreciably, set by the barrier potential of the material. Germanium junctions are lower, around 0.3 V. Values well above 0.7 V would indicate excessive current or a different device type.

Question 34Electronic Fundamentals

The primary function of a capacitor in an electronic circuit is to:

  1. Convert alternating current into direct current
  2. Store energy in an electric field Correct answer.
  3. Limit current flow in one direction
  4. Amplify the voltage of a signal

Explanation

A capacitor stores charge and therefore energy in the electric field between its plates. Its opposition to current depends on frequency, which is why it is used for coupling, filtering and timing. Rectification and one-way conduction are diode functions, and amplification is a transistor function.

Question 35Electronic Fundamentals

A resistor has coloured bands of brown, black, red and gold. What is its nominal value and tolerance?

  1. 100 ohm, 10 percent
  2. 1000 ohm, 10 percent
  3. 1000 ohm, 5 percent Correct answer.
  4. 10 ohm, 5 percent

Explanation

Brown is 1, black is 0, giving the digits 10, and red is a multiplier of 100, so the value is 1000 ohm. Gold in the fourth band indicates a tolerance of plus or minus 5 percent. Silver would indicate 10 percent.

Question 36Electronic Fundamentals

In a bipolar junction transistor operating in its active region, the collector current is principally controlled by:

  1. The base current Correct answer.
  2. The junction temperature
  3. The emitter doping level
  4. The collector-emitter voltage

Explanation

In the active region the collector current is approximately beta times the base current, so the base current is the controlling input. Collector-emitter voltage has only a small effect on collector current in this region. Doping and temperature influence behaviour but are not the control variable.

Question 37Electronic Fundamentals

A half-wave rectifier is supplied from a 50 Hz AC source. The ripple frequency of its output is:

  1. 150 Hz
  2. 50 Hz Correct answer.
  3. 100 Hz
  4. 25 Hz

Explanation

A half-wave rectifier passes only one half of each input cycle, so it produces one output pulse per input cycle. The ripple frequency therefore equals the supply frequency, 50 Hz. A full-wave rectifier would double this to 100 Hz.

Question 38Electronic Fundamentals

An operational amplifier connected as a voltage follower has a voltage gain of approximately one because:

  1. Its inputs are driven differentially
  2. Its open-loop gain is very low
  3. Its input impedance is very high
  4. Its output is fed back to its inverting input Correct answer.

Explanation

With the output returned directly to the inverting input, negative feedback forces the inverting input to track the non-inverting input, giving unity gain. The very high open-loop gain makes the closed-loop gain depend almost entirely on the feedback network. High input impedance and differential inputs are useful properties but do not by themselves set unity gain.

Question 39Electronic Fundamentals

A zener diode is to be used as a shunt voltage regulator. For stable regulation it must be:

  1. Forward biased with the load in series
  2. Reverse biased and operated in its breakdown region Correct answer.
  3. Forward biased and operated below its knee voltage
  4. Reverse biased and operated below its knee voltage

Explanation

Regulation relies on the near-constant reverse voltage that appears once the zener enters controlled breakdown. The series resistor must limit current so the zener stays above its knee current but within its power rating. Operating below the knee gives an unstable, load-dependent voltage, and forward bias gives only a normal diode drop.

Question 40Electronic Fundamentals

In a three-phase, six-diode full-wave rectifier fed from a 400 Hz supply, the fundamental ripple frequency of the DC output is:

  1. 1200 Hz
  2. 2400 Hz Correct answer.
  3. 400 Hz
  4. 4800 Hz

Explanation

A six-pulse bridge produces six output pulses per input cycle, so the ripple frequency is six times the supply frequency. Six times 400 Hz gives 2400 Hz. This higher ripple frequency allows smaller filter components than a single-phase supply would require.

Question 41Digital Techniques / Electronic Instrument Systems

In a digital data bus used on aircraft, what is the primary purpose of the parity bit?

  1. To synchronise the transmitter and receiver clocks
  2. To encrypt the transmitted data word
  3. To increase the data throughput of the bus
  4. To detect single-bit errors during transmission Correct answer.

Explanation

A parity bit is appended to a data word so the receiver can check whether the total number of set bits matches the agreed odd or even convention. A mismatch signals that a bit has changed in transit. Parity detects errors but does not correct them or provide timing or security.

Question 42Digital Techniques / Electronic Instrument Systems

An electronic instrument display uses a liquid crystal matrix. Which statement describes how a pixel in a passive-matrix LCD is addressed?

  1. By heating a thermochromic element at the pixel location
  2. By directing a beam of electrons onto a phosphor dot
  3. By moving a small mirror to reflect an external light source
  4. By applying a voltage across the intersection of a selected row and column electrode Correct answer.

Explanation

In a passive-matrix LCD the pixel sits at the crossing of a row electrode and a column electrode, and the voltage difference applied across that intersection controls the liquid crystal. This multiplexed addressing is what allows a grid of pixels to be driven with relatively few connections.

Question 43Digital Techniques / Electronic Instrument Systems

A flight deck display shows a red horizontal line across the screen where a system parameter should be displayed. In the context of electronic instrument systems, what does this most likely indicate?

  1. The sensor is operating in its normal calibration band
  2. A valid but out-of-range parameter is being displayed
  3. The parameter has been selected for trend monitoring
  4. The display unit has failed and the data is invalid Correct answer.

Explanation

Colour conventions on electronic displays reserve red for warnings and for invalid or failed data. A red line replacing a parameter typically means the display unit or its data source has failed, so the value cannot be trusted. Valid out-of-range values are usually shown by other cues such as amber or flashing.

Question 44Digital Techniques / Electronic Instrument Systems

An analogue sensor output is converted to digital form by an 8-bit ADC with a full-scale input range of 0 to 5 V. What is the resolution of this converter?

  1. 5.0 mV
  2. 39.1 mV
  3. 19.6 mV Correct answer.
  4. 9.8 mV

Explanation

An 8-bit converter divides the full-scale range into 2^8 = 256 steps. Dividing 5 V by 256 gives approximately 0.0195 V, or about 19.6 mV per step. This step size is the smallest input change the converter can resolve.

Question 45Digital Techniques / Electronic Instrument Systems

Two avionics units exchange data over a serial bus using a protocol in which each transmitted frame begins with a defined start sequence and ends with a checksum. What is the main function of the start sequence?

  1. It corrects any bit errors introduced during transmission
  2. It allows the receiver to identify the beginning of a valid frame Correct answer.
  3. It converts the serial data into parallel form for the receiver
  4. It stores the address of the transmitting unit permanently

Explanation

A start sequence is a recognisable pattern that lets the receiving unit detect where a frame begins and align its bit sampling accordingly. It is a framing aid, not an error-correction or address-storage mechanism.

Question 46Digital Techniques / Electronic Instrument Systems

An aircraft uses a digital data bus in which each LRU is connected to a single twisted pair that carries all traffic, and each receiver filters messages by an identifier label. Which bus architecture does this describe?

  1. A dedicated discrete-wire architecture
  2. A star-coupled point-to-point architecture
  3. A multidrop broadcast architecture Correct answer.
  4. A parallel backplane architecture

Explanation

When all units share one bus and every receiver sees all messages but selects those with matching identifiers, the architecture is a multidrop broadcast bus. This is characteristic of label-filtered serial data buses used in avionics.

Question 47Digital Techniques / Electronic Instrument Systems

A flight deck display is described as having a redundancy architecture in which two independent symbol generators drive a single display unit. What is the principal benefit of this arrangement?

  1. It maintains display availability if one generator fails Correct answer.
  2. It reduces the wiring weight of the display system
  3. It removes the need for any built-in test equipment
  4. It allows the display to show two different parameters at once

Explanation

Redundant symbol generators provide a backup path so that loss of one generator does not blank the display; the remaining generator continues to drive the unit. This improves dispatch reliability and safety rather than adding new display functions.

Question 48Digital Techniques / Electronic Instrument Systems

A digital instrument system samples an analogue pressure signal at 100 Hz. According to the Nyquist criterion, what is the highest signal frequency that can be faithfully represented without aliasing?

  1. 25 Hz
  2. 50 Hz Correct answer.
  3. 100 Hz
  4. 200 Hz

Explanation

The Nyquist criterion states that the sampling rate must be at least twice the highest frequency of interest. With a 100 Hz sampling rate, the maximum faithfully represented frequency is 50 Hz. Frequencies above this would alias into the sampled data.

Question 49Materials and Hardware

Which aluminium alloy series is the primary choice for high-strength aircraft structural components after suitable heat treatment?

  1. 3000 series
  2. 7000 series Correct answer.
  3. 1000 series
  4. 2000 series

Explanation

The 7000 series, alloyed mainly with zinc and magnesium, can be heat treated to the highest strengths of the aluminium families and is widely used for primary structural parts. The 2000 series is also heat treatable but generally achieves lower peak strength.

Question 50Materials and Hardware

In the 2024-T3 designation, what does the 'T3' temper indicate?

  1. Annealed after cold working
  2. Solution heat treated and artificially aged
  3. Solution heat treated, cold worked and naturally aged Correct answer.
  4. Strain hardened only

Explanation

The T3 temper means the alloy was solution heat treated, then cold worked to improve strength, and finally naturally aged at room temperature. Artificial ageing would be denoted by a different T number such as T6.