DGCA Technical General: Fuel Systems Questions
110 exam-style Fuel Systems questions for the DGCA Technical Generalpaper (CPL & ATPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
- Q1
The advantage of a float type fuel gauging system is 1. Simple 2. Compensates for variations of SG 3. Reads fuel quantity by mass 4. Compensates for change of aircraft attitude
- A 3 & 4
- B 2 & 3
- C 1 only
- D 1 & 3
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Correct answer: C. 1 only
The only real advantage of a float-type gauging system is its simplicity. Floats sense fuel level, effectively volume, so the indication cannot compensate for changes in specific gravity, cannot read mass, and is affected by changes of aircraft attitude.
- Q2
The function of baffle check valves in a fuel tank is
- A To reduce fuel flow at altitude
- B To prevent fuel surge during manoeuvring
- C To prevent pump cavitation
- D To prevent movement of fuel to the wingtip
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Correct answer: D. To prevent movement of fuel to the wingtip
Baffle check valves are one-way flap valves fitted in the tank ribs: they allow fuel to flow inboard towards the boost pumps but close against outboard flow, preventing fuel from migrating to the wingtip during wing-low manoeuvres. This keeps the pump inlets covered and the wing loading distribution controlled.
- Q3
In an aircraft with a fuel dumping system it will allow fuel to be dumped
- ADown to a predetermined safe value
- B Down to unuseable value
- C To leave 15 gallons in each tank
- D Down to maximum landing weight
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Correct answer: A. Down to a predetermined safe value
Fuel jettison systems are designed so that dumping stops at a predetermined safe fuel quantity, ensuring enough fuel remains for a go-around and diversion as required by certification rules. The system does not run tanks to unusable fuel, nor does it sense maximum landing weight.
- Q4
On what principle does a fuel flow meter work
- A Volume and viscosity
- BQuantity of movement
- C Capacitive dielectric
- D Pressure and temperature
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Correct answer: B. Quantity of movement
A fuel flow meter senses the momentum, or quantity of movement, imparted to the fuel stream, typically by a swirling impeller that a turbine element then resists in proportion to mass flow. This momentum principle gives an accurate mass-flow indication independent of fuel density changes.
- Q5
If a fuel sample appears cloudy, this is
- A An indication of air in the fuel
- B Normal
- C Due to the addition of FSII
- D An indication of water in the fuel
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Correct answer: D. An indication of water in the fuel
Clean aviation fuel should be clear and bright; a cloudy or hazy appearance indicates suspended water droplets emulsified in the fuel. Clear fuel with droplets settling to the bottom signals water contamination that must be drained off before flight.
- Q6
Vapour locks are caused by ________ Blocking the flow?
- AEvaporated fuel
- BWater vapour
- CAir
- DAnti-icing agent
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Correct answer: A. Evaporated fuel
This Explanation is Coming Soon
- Q7
The function of the baffles in a fuel tank is
- A To prevent movement of fuel to the wingtip
- B To prevent fuel surge (or sloshing) during manoeuvring
- C To prevent pump cavitation
- D To reduce fuel flow at altitude
Show answer
Correct answer: B. To prevent fuel surge (or sloshing) during manoeuvring
Baffles divide the tank interior and restrict the free movement of fuel, preventing it from surging or sloshing violently during manoeuvres and attitude changes. This keeps the fuel over the boost pumps and limits shifts in the aircraft centre of gravity.
- Q8
What voltage is supplied to booster pumps on a modern jet airliner
- A 115v AC single phase
- B 200v AC three phase
- C 28v DC from an inverter
- D 12v DC from the battery
Show answer
Correct answer: B. 200v AC three phase
Fuel booster (boost) pumps on a modern jet airliner are powered from the 115/200 V three-phase AC system, the three-phase supply suiting the induction motors that drive these high-capacity pumps.
- Q9
In a compensated capacitance fuel contents system what happens to a fuel weight of 8000lbs if its volume increases by 5%
- ADecreases by 5%
- B Increases by 5%
- CRemains the same
- D Increases by 5% for every degree rise in temperature
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Correct answer: C. Remains the same
A compensated capacitance system measures fuel mass, not volume, so an 8000 lb quantity remains 8000 lb even if the fuel expands 5% in volume with temperature. As the fuel warms and expands its density falls proportionally, so the indicated weight is unchanged.
- Q10
Fuel tanks accumulate moisture, the most practical way to limit this in an aircraft flown daily is to:
- A Secure the filler cap tightly and plug the drains
- B Drain the tank at the end of each day
- CFill the tank after each flight
- D Drain the water before flight
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Correct answer: C. Fill the tank after each flight
Filling the tanks after each flight leaves little airspace above the fuel, so there is minimal moist air to condense as the temperature falls overnight. This is the most practical way to limit water accumulation in a daily-flown aircraft.
- Q11
Fuel tanks are vented through?
- AThe fuel feed lines
- BThe bleed lines
- CThe return lines
- DPressure relief values at the wing tips
Show answer
Correct answer: D. Pressure relief values at the wing tips
This Explanation is Coming Soon
- Q12
How are modern passenger jet aircraft fuel tanks pressurised
- A By nitrogen from a storage cylinder
- B By ram air through the vent system
- C By bleed air from the pneumatic system
- D By a volumetric top off unit
Show answer
Correct answer: B. By ram air through the vent system
Modern jet fuel tanks are kept at a slight positive pressure by ram air admitted through the vent (surge) tank system, which also allows the tanks to breathe as fuel is used and as altitude changes.
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