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DGCA CPL Tech Specific study materials
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DGCA CPL Tech Specific practice questions

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Question 1Aircraft - Technical Specific (airframe, systems and powerplant)

On a light aircraft with a fixed-pitch propeller, what happens to engine RPM when the aircraft climbs at constant throttle setting?

  1. RPM increases because the propeller unloads as air density decreases Correct answer.
  2. RPM remains constant because the throttle is unchanged
  3. RPM increases because manifold pressure rises with altitude
  4. RPM decreases because air density and propeller load resistance fall

Explanation

As altitude increases, air density falls, so each blade section meets less resistance and the propeller absorbs less power from the engine, allowing RPM to rise at a fixed throttle setting. The throttle valve position is unchanged, so the change comes from propeller loading, not from more mixture entering the cylinders.

Question 2Aircraft - Technical Specific (airframe, systems and powerplant)

In a four-stroke reciprocating engine, during which stroke is the intake valve open and the piston moving toward bottom dead centre?

  1. Power stroke
  2. Intake stroke Correct answer.
  3. Exhaust stroke
  4. Compression stroke

Explanation

The intake stroke draws the fuel-air charge into the cylinder while the intake valve is open and the piston travels from top dead centre to bottom dead centre. The other three strokes involve the valves closed in various combinations and the piston moving in the opposite direction or against compression.

Question 3Aircraft - Technical Specific (airframe, systems and powerplant)

What is the primary function of the magneto in an aircraft piston engine ignition system?

  1. To step down bus voltage for the spark plug electrodes
  2. To generate a high-tension voltage that fires the spark plugs independently of the aircraft battery Correct answer.
  3. To advance the ignition timing automatically with altitude
  4. To regulate the charging rate of the aircraft battery during flight

Explanation

A magneto is a self-contained generator that produces its own electrical energy from engine rotation and delivers high-tension pulses to the spark plugs. Because it does not rely on the aircraft battery, the engine keeps firing even if the electrical system fails.

Question 4Aircraft - Technical Specific (airframe, systems and powerplant)

Which component converts the reciprocating motion of the pistons into rotary motion of the crankshaft?

  1. Connecting rod Correct answer.
  2. Valve lifter
  3. Pushrod
  4. Camshaft

Explanation

The connecting rod joins the piston to the crankshaft journal, and as the piston reciprocates the rod swings through an arc that turns the crankshaft. The camshaft, lifters and pushrods belong to the valve train and do not transmit power to the crankshaft.

Question 5Aircraft - Technical Specific (airframe, systems and powerplant)

In a semi-monocoque wing structure, what is the main role of the stringers?

  1. They form the fuel-tight boundary of the integral tanks
  2. They provide the hinge attachment for the flaps
  3. They stiffen the skin against buckling and help carry bending loads Correct answer.
  4. They carry the entire bending load in place of the spar

Explanation

Stringers run spanwise and are riveted to the skin, stiffening it against compressive buckling while sharing bending loads with the spar caps. The spars remain the primary bending members, and flap hinges and tank sealing are separate design functions.

Question 6Aircraft - Technical Specific (airframe, systems and powerplant)

What is the purpose of a fuel strainer or gascolator fitted at the low point of a light aircraft fuel system?

  1. To increase fuel pressure before the carburettor
  2. To trap water and coarse sediment before the fuel reaches the carburettor Correct answer.
  3. To measure the rate of fuel flow to the engine
  4. To prevent fuel vapour from forming in the lines

Explanation

The gascolator is placed at the lowest point so that water and sediment collect there and can be drained during the pre-flight check, protecting the carburettor from contamination. It is a filter, not a pump, flow meter or vapour separator.

Question 7Aircraft - Technical Specific (airframe, systems and powerplant)

Which of the following is the correct purpose of an aircraft's pitot-static system?

  1. To supply dynamic pressure to the vertical speed indicator only
  2. To measure outside air temperature for the airspeed indicator
  3. To supply static pressure to the airspeed indicator and pitot pressure to the altimeter
  4. To provide total pressure to the airspeed indicator and static pressure to the altimeter and vertical speed indicator Correct answer.

Explanation

The pitot tube supplies total (impact) pressure to the airspeed indicator, while the static ports supply undisturbed static pressure to the airspeed indicator, altimeter and vertical speed indicator. Comparing total and static pressure gives dynamic pressure and hence airspeed.

Question 8Aircraft - Technical Specific (airframe, systems and powerplant)

What is the function of the voltage regulator in a light aircraft DC charging system?

  1. To limit generator or alternator output voltage to a safe value across the bus Correct answer.
  2. To disconnect the battery from the bus during engine start
  3. To convert alternating current to direct current for the avionics bus
  4. To reduce the field current to zero when the master switch is turned off

Explanation

The voltage regulator controls the field current so that generator or alternator output stays within a set range, protecting the battery and electrical equipment from overvoltage. Rectification of AC to DC is done by the alternator's own rectifier pack, not by the regulator.

Question 9Aircraft - Technical Specific (airframe, systems and powerplant)

A normally aspirated engine shows a manifold pressure of 20 inHg at sea level with the throttle fully open. What manifold pressure would you expect with the throttle fully open at a higher altitude on a standard day?

  1. Approximately the same value, because throttle position is unchanged
  2. A lower value, because ambient pressure has decreased Correct answer.
  3. Zero, because the engine cannot run above sea level
  4. A higher value, because the throttle is still fully open

Explanation

With the throttle fully open, manifold pressure closely reflects ambient pressure, which falls as altitude increases. The throttle position does not maintain pressure; the reduced outside pressure is what appears in the manifold.

Question 10Aircraft - Technical Specific (airframe, systems and powerplant)

During a magneto check, the engine RPM drops 150 RPM when the right magneto is selected and 40 RPM when the left magneto is selected. What is the most likely interpretation?

  1. The right magneto circuit is faulty or its timing is incorrect Correct answer.
  2. Both magnetos are performing normally
  3. The engine is running too lean and the mixture should be enriched first
  4. The left magneto is faulty because its drop is smaller

Explanation

An excessive drop on one magneto indicates a problem in that circuit, such as a fouled plug, faulty harness or incorrect internal timing, because that magneto alone is producing weak combustion. The other magneto shows an acceptable drop, so the fault lies with the right side.

Question 11Aircraft - Technical Specific (airframe, systems and powerplant)

An aircraft is parked with a full fuel tank and the fuel selector on BOTH. During the pre-flight drain check, water is found in the gascolator. What is the correct action?

  1. Drain until clean fuel appears, then check all sumps again before flight Correct answer.
  2. Ignore it because the engine-driven pump will pass the water through
  3. Add a fuel system drier to absorb the remaining water
  4. Run the engine briefly to purge the water through the exhaust

Explanation

Water is denser than avgas and collects at the lowest drain points, so continued draining until only clean fuel appears is the accepted method. All sumps should then be rechecked because water may remain elsewhere in the system.

Question 12Aircraft - Technical Specific (airframe, systems and powerplant)

What is the effect of a broken or disconnected exhaust muffler shroud on a cabin-heated aircraft?

  1. Cabin heat output increases because more hot air reaches the cabin
  2. The engine will lose manifold pressure and stop
  3. The cabin heat valve will automatically close
  4. Carbon monoxide from exhaust gases may enter the cabin heating air Correct answer.

Explanation

Cabin heat is taken from air that passes over the exhaust muffler shroud; a crack or failed shroud seal allows exhaust gas, including carbon monoxide, to mix with that heated air. This is why exhaust systems are inspected closely and CO detectors are used.

Question 13Aircraft - Technical Specific (airframe, systems and powerplant)

An engine is fitted with a constant-speed propeller and the pilot notes that manifold pressure is 22 inHg and RPM is 2200 in level flight. If the pilot increases the propeller control setting without changing the throttle, what happens?

  1. RPM decreases and manifold pressure rises slightly Correct answer.
  2. RPM increases and manifold pressure falls slightly
  3. RPM increases and manifold pressure rises
  4. RPM and manifold pressure both remain unchanged

Explanation

Increasing the propeller control setting increases blade angle, which loads the engine more and reduces RPM; the reduced airflow causes manifold pressure to rise slightly at the fixed throttle. This is the normal interaction between propeller load and manifold pressure in a constant-speed system.

Question 14Aircraft - Technical Specific (airframe, systems and powerplant)

What is the primary purpose of the primer in a light aircraft piston engine?

  1. To supply extra fuel for starting when the engine is cold Correct answer.
  2. To purge air from the fuel lines before start
  3. To increase fuel pressure at the carburettor inlet
  4. To enrich the mixture during cruise at high altitude

Explanation

The primer injects fuel directly into the induction system or cylinders to provide a rich enough mixture for starting, especially in cold conditions when fuel vaporisation is poor. It is not used for cruise enrichment or line purging.

Question 15Aircraft - Technical Specific (airframe, systems and powerplant)

Aircraft skin panels are often bonded as well as riveted in modern structures. What is the main structural benefit of bonding?

  1. It eliminates the need for any internal structure
  2. It allows the skin to be removed easily for inspection
  3. It increases the electrical conductivity of the airframe only
  4. It distributes load over a larger area and improves fatigue resistance Correct answer.

Explanation

Adhesive bonding spreads load across the joint rather than concentrating it at rivet holes, which reduces stress concentrations and improves fatigue life. It complements, rather than replaces, the internal structure.

Question 16Aircraft - Technical Specific (airframe, systems and powerplant)

During a pre-flight inspection, a control cable is found to have a single broken strand near a pulley. What is the correct course of action?

  1. Shorten the cable to remove the damaged section and re-rig it
  2. Return the aircraft to service because one broken strand is within tolerance
  3. Apply a protective sleeve over the affected area and continue
  4. Refer the cable for maintenance action according to the approved limits before flight Correct answer.

Explanation

Control cable condition is governed by approved inspection criteria, and a broken strand near a pulley indicates wear and possible internal damage that must be assessed before flight. Field repairs such as sleeving or shortening are not acceptable without approved data.

Question 17Aircraft - Technical Specific (airframe, systems and powerplant)

What is the function of the crankcase breather in a piston engine?

  1. To supply oil to the rocker boxes under pressure
  2. To vent fuel vapour from the carburettor bowl
  3. To provide a vacuum source for the gyroscopic instruments
  4. To allow blow-by gases and pressure to escape from the crankcase Correct answer.

Explanation

The breather prevents pressure build-up in the crankcase from piston blow-by and allows moisture and vapours to escape, which helps avoid seal damage and oil being forced past gaskets. It is separate from the oil feed, fuel venting and vacuum systems.

Question 18Aircraft - Technical Specific (airframe, systems and powerplant)

In a hydraulically operated landing gear system, what is the purpose of the selector valve?

  1. To filter contaminants from the hydraulic fluid
  2. To direct hydraulic pressure to the extend or retract side of the actuating cylinders Correct answer.
  3. To store hydraulic fluid under pressure for emergency use
  4. To limit system pressure to a preset value

Explanation

The selector valve routes pressurised fluid to the appropriate side of the gear actuators so the gear extends or retracts, and it also allows fluid to return to the reservoir. Pressure limiting, storage and filtration are performed by other components.

Question 19Aircraft - Technical Specific (airframe, systems and powerplant)

An aircraft alternator warning light stays illuminated after engine start with the alternator switch on. Which condition is most consistent with this indication?

  1. The battery is fully charged and the alternator is off load
  2. The alternator field circuit is open or the alternator is not producing output Correct answer.
  3. The starter relay has remained engaged
  4. The voltage regulator is limiting output correctly

Explanation

A warning light that remains on indicates the alternator is not supplying the bus, commonly because the field circuit is open, the drive has failed or the alternator itself is faulty. A correctly charging system extinguishes the light once output is established.

Question 20Aircraft - Technical Specific (airframe, systems and powerplant)

Why are turbine engine compressor blades in the later stages made progressively shorter than those in the early stages?

  1. To allow more cooling air to reach the combustion chamber
  2. To match the reduced volume of air as it is compressed along the axis Correct answer.
  3. To reduce the rotational speed of the rear stages
  4. To decrease the pressure ratio across each stage

Explanation

As air passes through the compressor its pressure rises and its volume decreases, so later stages need smaller annulus areas and shorter blades to maintain correct velocities. All stages rotate together on the same shaft, so the change is geometric rather than a speed change.

Question 21Aircraft - Technical Specific (airframe, systems and powerplant)

A piston engine is running with the mixture excessively lean at high power. What is the main risk?

  1. Carburettor icing because the mixture is too rich
  2. Excessive oil consumption because of low cylinder pressure
  3. Detonation and high cylinder head temperatures due to inadequate fuel cooling Correct answer.
  4. Spark plug fouling from unburned lead

Explanation

At high power a lean mixture burns hotter and can promote detonation and excessive cylinder head temperatures, because fuel provides charge cooling and detonation suppression. Rich mixtures, not lean ones, cause plug fouling and are used for cooling at high power.

Question 22Aircraft - Technical Specific (airframe, systems and powerplant)

In a twin-engine aircraft with a constant-speed, feathering propeller, what happens to the propeller blade angle when the engine is shut down and the propeller is feathered?

  1. Blades rotate to a negative angle to produce reverse thrust
  2. Blades rotate to a fine angle to increase drag and slow the aircraft
  3. Blades rotate to a coarse angle that aligns them with the relative airflow to minimise drag Correct answer.
  4. Blades remain at the flight angle and windmill at high RPM

Explanation

Feathering turns the blades to a high (coarse) angle so their leading edges face the relative airflow, presenting minimum area and stopping rotation, which reduces drag after an engine failure. Fine pitch would increase drag and windmilling.

Question 23Aircraft - Technical Specific (airframe, systems and powerplant)

A wing spar is designed with upper and lower caps of different cross-sectional area. Which statement best explains this design?

  1. The upper cap is larger because tension loads are always greater than compression loads
  2. The caps are sized only by the attachment fittings for the flaps
  3. Both caps are equal because bending loads reverse in all flight conditions
  4. The lower cap is larger to resist the tensile loads on the lower surface in positive flight Correct answer.

Explanation

In positive flight the wing bends upward, putting the lower surface in tension and the upper surface in compression, so the lower cap is often sized for tensile strength and fatigue while the upper cap resists buckling. The caps are not sized by flap fittings, and load reversal is considered separately.

Question 24Aircraft - Technical Specific (airframe, systems and powerplant)

During a run-up, an engine with a fixed-pitch propeller shows a normal magneto drop but a significant rise in RPM when carburettor heat is applied. What does this indicate?

  1. The engine is developing excess power from the heat
  2. The mixture is too rich, and carburettor heat leans it toward a better setting Correct answer.
  3. The carburettor heat valve is stuck closed
  4. The magneto timing is retarded

Explanation

Applying carburettor heat reduces air density, which richens the mixture further; an RPM rise instead of the expected drop indicates the mixture was already too rich and heat leaned it toward a better ratio. A stuck heat valve or retarded timing would not produce this specific response.

Question 25Aircraft - Technical Specific (airframe, systems and powerplant)

What is the purpose of the diffuser in a gas-turbine engine combustion chamber?

  1. To cool the turbine blades with bypass air
  2. To reduce air velocity and raise static pressure so combustion is stable Correct answer.
  3. To mix fuel with exhaust gas after the turbine
  4. To increase air velocity before combustion

Explanation

The diffuser slows the high-velocity compressor discharge air and converts dynamic pressure into static pressure, creating conditions in which fuel can burn stably without being blown out. Increasing velocity would make flame holding more difficult.

Question 26Aircraft - Technical Specific (airframe, systems and powerplant)

In a light aircraft's landing gear, what is the function of the torque link (scissors) assembly attached to the shock strut?

  1. It provides the hydraulic damping that absorbs landing shock
  2. It keeps the wheel aligned with the direction of travel while still allowing the strut to compress and extend Correct answer.
  3. It locks the gear in the down position after extension
  4. It carries the vertical landing loads from the axle directly into the wing spar

Explanation

The torque links connect the upper and lower halves of the shock strut so that the piston cannot rotate inside the cylinder, which keeps the wheel pointing straight ahead. Because the links are hinged, they fold and unfold as the strut compresses and extends, so they transmit torque but not vertical load. Vertical loads pass through the strut itself, and damping is produced by the internal metering of hydraulic fluid.

Question 27Aircraft - Technical Specific (airframe, systems and powerplant)

A reciprocating engine is fitted with an air-cooled cylinder head. Which feature is mainly responsible for keeping the exhaust valve area cooler than the rest of the head?

  1. A sodium-filled stem that transfers heat from the valve head to the guide Correct answer.
  2. A shrunk-in valve seat insert of high-conductivity material
  3. A bronze or sintered valve guide with a close tolerance
  4. An inter-cylinder baffle that blocks airflow at the rear of the engine

Explanation

A sodium-filled exhaust valve stem is partly filled with metallic sodium, which melts in service and, because it is flung up and down by valve motion, carries heat from the valve head to the guide and then to the cylinder head. This keeps exhaust valve head temperatures well below the level at which the metal loses strength. The guide and seat insert assist heat transfer but do not provide the internal heat-pumping action.

Question 28Aircraft - Technical Specific (airframe, systems and powerplant)

An aircraft battery is rated 24 V, 17 Ah. During a ground check with the alternator off, a 10 A load is connected. Ignoring efficiency and end-of-discharge effects, approximately how long will the battery sustain the load?

  1. 0.6 hour
  2. 2.4 hours
  3. 10 hours
  4. 1.7 hours Correct answer.

Explanation

Capacity in ampere-hours divided by the discharge current gives the nominal discharge time: 17 Ah / 10 A = 1.7 hours. This is an idealised figure because the usable capacity falls at high discharge rates and the battery voltage declines as it discharges. The calculation nevertheless shows the order of magnitude a pilot should expect.

Question 29Aircraft - Technical Specific (airframe, systems and powerplant)

What is the primary purpose of the baffles and seals installed around an air-cooled engine in a tractor installation?

  1. To support the weight of the engine accessories
  2. To reduce engine noise radiated into the cabin
  3. To force cooling air to flow through the cylinder fins instead of bypassing them Correct answer.
  4. To prevent oil mist from reaching the magnetos

Explanation

Air follows the path of least resistance, so without baffles most of the cooling air would flow around the engine rather than between the closely spaced fins. Baffles and flexible seals form a plenum that forces the air through the fin passages, where heat is transferred to it. Poor baffling is a classic cause of high cylinder head temperatures in the climb.

Question 30Aircraft - Technical Specific (airframe, systems and powerplant)

A pilot notices that cylinder head temperature rises sharply and oil temperature also climbs during a prolonged climb, while oil pressure remains normal. Which combination of factors best explains this?

  1. An over-rich mixture causing excessive carbon formation
  2. A shorted oil temperature gauge circuit
  3. Low airspeed with high power, giving inadequate cooling airflow and high heat rejection Correct answer.
  4. A failed oil pressure relief valve dumping oil back to the sump

Explanation

In a long climb the engine produces high power, so it rejects a large amount of heat to the oil and cylinder fins, while the low airspeed and reduced mass flow of cooling air remove that heat less effectively. The result is a simultaneous rise in both cylinder head and oil temperature. The correct response is to reduce power, lower the nose or increase airspeed, and enrich the mixture as required.

Question 31Aircraft - Technical Specific (airframe, systems and powerplant)

Which statement correctly describes how a constant-speed propeller governor responds when engine RPM tends to rise above the selected value?

  1. It increases oil pressure to the propeller, driving the blades towards coarse pitch Correct answer.
  2. It reduces oil pressure to the propeller, allowing the blades to move towards coarse pitch
  3. It disconnects the propeller from the engine until RPM falls
  4. It increases oil pressure to the propeller, driving the blades towards fine pitch

Explanation

The governor senses RPM through a flyweight assembly and controls oil flow to the propeller. If RPM rises above the setting, the flyweights move outwards and the pilot valve directs increased oil pressure to the propeller, moving the blades to a coarser pitch, which increases the aerodynamic load and slows the engine. This feedback loop holds RPM essentially constant as power or airspeed changes.

Question 32Aircraft - Technical Specific (airframe, systems and powerplant)

A fuel-injected light aircraft engine is being started hot and the engine fails to fire. Which technique is most appropriate?

  1. Use the boost pump and mixture rich with the throttle wide open
  2. Prime repeatedly with the electric primer while cranking
  3. Close the throttle fully and crank with mixture rich
  4. Leave mixture idle cut-off and crank with the throttle open to clear vapour, then introduce mixture Correct answer.

Explanation

In a hot engine the fuel lines and injector lines can contain vapour, and the fuel control unit may have residual fuel, producing an over-rich condition. Cranking with the mixture at idle cut-off and the throttle open purges the vapour and clears excess fuel, after which the mixture can be introduced smoothly as the engine catches. This is the standard hot-start procedure for many injected engines.

Question 33Aircraft - Technical Specific (airframe, systems and powerplant)

What is the main function of the compressor bleed valves (start bleed valves) on a turbojet engine during start and low-power operation?

  1. To supply pressurisation air to the cabin at idle
  2. To prevent compressor surge by reducing delivery pressure and axial load on the front stages Correct answer.
  3. To increase fuel flow to the combustor at low RPM
  4. To cool the turbine blades during start

Explanation

At low rotational speeds the rear compressor stages cannot accept the volume delivered by the front stages, so the pressure ratio becomes unstable and the compressor may surge or stall. Bleed valves open to release some air into the bypass duct or overboard, reducing the pressure and axial load on the front stages and keeping the airflow matched. They close as RPM and pressure ratio rise into the stable operating range.

Question 34Aircraft - Technical Specific (airframe, systems and powerplant)

Why are the blades of the first turbine stage in a gas-turbine engine often made hollow and fed with cooling air?

  1. To reduce the pressure ratio across the turbine stage
  2. To reduce the centrifugal stress at the blade root while allowing operation at gas temperatures above the material limit Correct answer.
  3. To allow the blade to be forged rather than cast
  4. To increase the mass of the rotor for smoother idle running

Explanation

Turbine entry temperatures are high enough to exceed the melting or creep limit of the blade alloy if the blade were solid. Hollow, film-cooled blades use compressor air to keep the metal cooler, while the hollow construction and reduced mass lower the centrifugal stress at the root at high rotational speed. This combination allows higher turbine temperatures and therefore more thrust for a given size.

Question 35Aircraft - Technical Specific (airframe, systems and powerplant)

In a semi-monocoque wing, what is the role of the stringers attached to the skin?

  1. They stiffen the skin against buckling and help carry bending loads Correct answer.
  2. They provide attachment points for the engine mount
  3. They act as the primary fuel tank seal
  4. They carry the entire bending load instead of the spar caps

Explanation

Semi-monocoque construction relies on the skin to carry part of the bending and shear loads, but thin skin would buckle under compression without support. Stringers riveted to the skin divide it into smaller panels, raising the buckling stress, and they also pick up bending loads in their own right. Spar caps still carry the greatest share of the bending moment.

Question 36Aircraft - Technical Specific (airframe, systems and powerplant)

A pilot selects the landing gear down and the green light does not illuminate, but the gear horn does not sound and the gear appears down. Which condition is the most likely explanation?

  1. The down-lock microswitch or its bulb circuit has failed Correct answer.
  2. The gear is still in transit and the down-lock has not engaged
  3. The hydraulic pump has failed completely
  4. The gear selector valve is stuck in the up position

Explanation

If the gear were not down and locked, the warning horn would normally sound with the throttle retarded and the gear not down, so the absence of the horn together with a gear that appears extended points to an indication fault. A failed down-lock switch or bulb is the most likely cause. The correct action is to verify the gear visually if possible and treat the indication as unreliable.

Question 37Aircraft - Technical Specific (airframe, systems and powerplant)

What is the purpose of the check valve installed in the pressure line of a hydraulic system between the pump and the selector valves?

  1. To filter contaminants from the hydraulic fluid
  2. To allow the system to be hand-pumped in an emergency
  3. To limit the maximum system pressure
  4. To prevent pressure from the accumulator or actuator from back-feeding the pump Correct answer.

Explanation

A check valve permits flow in one direction only. In the pump delivery line it allows pressurised fluid to reach the system but blocks reverse flow, so accumulator pressure or actuator feedback cannot drive the pump backwards or leak away through a stationary pump. Pressure limiting is a separate function performed by the relief valve.

Question 38Aircraft - Technical Specific (airframe, systems and powerplant)

During a pre-flight walk-around, a small amount of clear fluid is found dripping from the engine cowling beneath the cylinder area after the aircraft has stood overnight. Which interpretation is most reasonable?

  1. It is certainly aviation fuel and the aircraft must be defuelled
  2. It indicates a cracked crankcase that makes the engine unairworthy
  3. It is probably condensed water or oil seepage past the piston rings and should be investigated before flight Correct answer.
  4. It is hydraulic fluid from the brake system

Explanation

Small amounts of oil can seep past the piston rings and valve guides into the lower cylinders when an engine stands, and condensation can also collect in the cowling. The fluid should be identified by smell and colour and the source traced, and a hydraulic lock check by turning the propeller is prudent before start. Unexplained fluid always warrants investigation, but it does not automatically mean the engine is unairworthy.

Question 39Aircraft - Technical Specific (airframe, systems and powerplant)

An aircraft has a 28 V DC system with a 24 V lead-acid battery and a 28 V alternator. What is the main reason the battery is not a 28 V unit?

  1. A 28 V battery would be too heavy for the aircraft
  2. The battery only supplies the emergency bus
  3. The alternator cannot charge a battery above 24 V
  4. Lead-acid cells are nominally 2 V each, so 12 cells give about 24 V, which suits the 28 V regulated bus Correct answer.

Explanation

Each lead-acid cell produces about 2 V on open circuit, so a 12-cell battery gives roughly 24 V nominal, and the charging system regulates the bus at about 28 V to drive current into it. The 28 V bus voltage is a charging and distribution level, not the battery's nominal voltage. This is why a 24 V battery is standard on aircraft described as 28 V systems.

Question 40Aircraft - Technical Specific (airframe, systems and powerplant)

A turbocharged piston engine is climbing with the waste gate fully closed. The pilot notices that manifold pressure remains at the selected value as altitude increases, but cylinder head temperature rises. Which explanation is most consistent?

  1. The mixture is too rich and is cooling the cylinders excessively
  2. The turbocharger is maintaining sea-level manifold pressure, so the engine is producing high power with a reduced cooling margin Correct answer.
  3. The waste gate is stuck open and boost is being lost
  4. The magnetos are mistimed and retarding the spark

Explanation

With the waste gate closed the turbocharger keeps raising the compressor delivery pressure as ambient pressure falls, so the engine keeps its rated manifold pressure and power up to the turbocharger's limit. Because the engine is working hard while the aircraft climbs into thinner, warmer air, the cooling margin is reduced and cylinder head temperature rises. The pilot must manage mixture and power and respect the turbocharger's temperature limits.

Question 41Flight performance, planning and loading

In aircraft mass-and-balance work, what does the datum refer to?

  1. The fixed reference point from which all longitudinal arm measurements are taken Correct answer.
  2. The aft limit beyond which the aircraft becomes unstable in pitch
  3. The point about which the aircraft is designed to rotate on take-off
  4. The centre of gravity position at maximum take-off mass

Explanation

The datum is an arbitrary but fixed reference plane or point, chosen by the manufacturer, from which all longitudinal arms (stations) are measured. Arms and moments are only meaningful when referred to the same datum, so the datum itself does not move with loading.

Question 42Flight performance, planning and loading

An aircraft has an empty mass of 1,200 kg at an arm of 2.0 m, and a pilot of 80 kg at an arm of 1.0 m. What is the loaded centre of gravity arm?

  1. 1.94 m Correct answer.
  2. 1.50 m
  3. 1.80 m
  4. 1.87 m

Explanation

Total mass is 1,280 kg. Total moment is (1,200 × 2.0) + (80 × 1.0) = 2,400 + 80 = 2,480 kg·m. Dividing moment by mass gives 2,480 / 1,280 = 1.9375 m, which rounds to 1.94 m.

Question 43Flight performance, planning and loading

Which condition describes the aircraft being in equilibrium about the lateral axis during the take-off run?

  1. The tail-down moment of the main wheels equals the nose-down moment of the tail
  2. The nose-up moment of the lift equals the nose-down moment of the weight
  3. The nose-down moment of the weight equals the nose-up moment of the main-wheel reaction Correct answer.
  4. The nose-down moment of the weight equals the nose-up moment of the tailplane download

Explanation

During the ground run the aircraft pivots about the main wheels. The weight acts at the CG ahead of that pivot, producing a nose-down moment, which is balanced by the nose-up moment of the reaction at the main wheels. This balance determines the load on the nose or tail wheel.

Question 44Flight performance, planning and loading

What is the effect on take-off ground roll of operating from an aerodrome with a pressure altitude higher than the elevation?

  1. Ground roll decreases because thrust increases in thinner air
  2. Ground roll is unchanged because only elevation affects performance
  3. Ground roll increases because density altitude is higher than elevation Correct answer.
  4. Ground roll decreases because the altimeter under-reads

Explanation

Pressure altitude above the aerodrome elevation means the actual air density corresponds to a higher altitude, so density altitude exceeds elevation. Lower density reduces engine power and propeller thrust and raises true airspeed for a given IAS, lengthening the ground roll.

Question 45Flight performance, planning and loading

An aircraft has a maximum structural take-off mass of 3,800 kg and a performance-limited take-off mass of 3,650 kg for the conditions. Which mass must be used for flight planning?

  1. 3,725 kg, the average of the two values
  2. 3,800 kg, because it is the certified limit
  3. 3,800 kg, provided the runway is long enough
  4. 3,650 kg, because performance is the more restrictive limit Correct answer.

Explanation

The regulated take-off mass is the lowest of the structural limit and all performance-limited masses (runway, climb, obstacle, tyre speed). Here performance restricts the aircraft to 3,650 kg, so that is the planning value.

Question 46Flight performance, planning and loading

Where is the centre of gravity located relative to the neutral point for an aircraft to have positive static longitudinal stability?

  1. Forward of the neutral point Correct answer.
  2. Aft of the neutral point
  3. Coincident with the neutral point
  4. At the aerodynamic centre of the wing

Explanation

Positive static stability in pitch requires the CG to be ahead of the neutral point, so that a disturbance produces a restoring moment. As the CG moves aft toward the neutral point, stability decreases and stick forces lighten.

Question 47Flight performance, planning and loading

Loading an aircraft beyond its aft CG limit most directly affects which characteristic?

  1. Flap limiting speed
  2. Take-off run and climb gradient
  3. Directional stability on the ground
  4. Longitudinal stability and control Correct answer.

Explanation

An aft CG reduces the static margin, so longitudinal stability and control degrade and recovery from a stall or upset becomes more difficult. The aircraft may also require less elevator force, giving a false sense of responsiveness.

Question 48Flight performance, planning and loading

An aeroplane is loaded such that its CG lies within limits at zero fuel mass but moves outside the forward limit when fuel is added in a fuselage tank located ahead of the CG. What is the correct planning action?

  1. Add ballast aft of the CG after take-off
  2. Reduce the take-off mass to the maximum landing mass
  3. Accept the condition because the zero-fuel CG is within limits
  4. Reduce fuel load or redistribute load so that the CG stays within limits throughout the flight Correct answer.

Explanation

The CG must remain within limits at all stages, including with fuel loaded and after fuel burn-off. If a forward fuselage tank pushes the CG ahead of the forward limit, fuel or payload must be redistributed to restore a compliant envelope throughout the flight.

Question 49Flight performance, planning and loading

What does the term 'basic empty mass' include that dry operating mass also includes?

  1. Crew, crew baggage and unusable fuel Correct answer.
  2. Payload and usable fuel
  3. Nothing; basic empty mass is always the larger figure
  4. Only the airframe and engines

Explanation

Basic empty mass covers the airframe, engines, equipment, unusable fuel and full operating fluids. Dry operating mass adds crew, crew baggage and catering or crew supplies, so it is the larger figure and is the basis for operational mass computations.

Question 50Flight performance, planning and loading

An aircraft with a mass of 1,050 kg has its CG at 2.30 m from the datum. A 50 kg item is moved from an arm of 1.10 m to an arm of 3.30 m. What is the new CG arm?

  1. 2.20 m
  2. 2.40 m Correct answer.
  3. 2.30 m
  4. 2.51 m

Explanation

Moving 50 kg through 2.20 m produces a moment change of 110 kg·m aft. Total mass is unchanged at 1,050 kg, so the CG shift is 110 / 1,050 = 0.105 m aft, giving 2.405 m, which is 2.40 m.