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NZCAA BGT Exam > Turbine Engine Fuel Systems > Flashcards

Turbine Engine Fuel Systems Flashcards

1
Q

How does the volatility of AVTUR compare to that of AVGAS?

A

The volatility of AVTUR is lower.

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2
Q

How does the calorific value of AVTUR compare to that of AVGAS?

A

The calorific value of AVTUR is higher.

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3
Q

How does the specific gravity of AVTUR compare to that of AVGAS?

A

The specific gravity of AVTUR is higher.

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4
Q

How does AVTUR’s propensity for absorbing water compare to that of AVGAS?

A

AVTUR has a higher propensity for absorbing water.

AVTUR holds significantly more water in suspension.

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5
Q

How does the flashpoint of AVTUR compare to that of AVGAS?

A

The flashpoint of AVTUR is higher.

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6
Q

What safety devices are used to prevent inadvertent selection of the wrong fuel?

A

Different color dyes added to the fuel.

The AVTUR delivery nozzle is too large to fit into an AVGAS tank.

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7
Q

By what names is turbine fuel known?

A

AVTUR; Jet A/ Jet A1; JP4/JP5; or F40/F35.

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8
Q

What is the difference between Jet A/ Jet A1 and JP4/ JP5?

A

In the United States, Jet A is often called JP4 and Jet A1 is often called JP5

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9
Q

Are turbine fuels required to have lubricating properties?

A

Yes

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10
Q

If alternative/emergency fuels are approved for use in an aircraft, in which document would this be specified?

A

In the aircraft flight manual.

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11
Q

Why is water contamination more of a problem in AVTUR than in AVGAS?

A

Water contamination is more of a problem in AVTUR than in AVGAS because AVTUR can hold significantly more water in suspension than can AVGAS.

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12
Q

How is water tested for in turbine fuel?

A

A chemical water check is carried out, where a tester changes color if an excessive amount of water is present in the fuel sample.

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13
Q

What are the common additives put into AVTUR?

A

Anti-icing and anti-microbiocidal additives are often added to AVTUR.

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14
Q

What is the ideal air to fuel ratio for combustion in a turbine engine?

A

The ideal (stochiometric) air to fuel ratio is 15:1.

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15
Q

When refueling, why is the fuel’s density measured and recorded?

A

To enable an accurate fuel weight to be calculated for the volume loaded.

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16
Q

Why is knowledge of fuel’s specific gravity (SG) relevant when refueling an aircraft?

A

Loading is in volume (liters or gallons), and to convert volume to weight (mass) the SG is required.

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17
Q

What is the specific gravity (SG) of Jet A1 at 15 °C?

A

Approx 0.8 kgs per liter (0.8 grams per mililitre )

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18
Q

Does the temperature of the fuel affect its specific gravity?

A

Yes, The relationship inversely proportional. That is, if the temperature increases the specific gravity reduces.

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19
Q

Does the specific gravity of a fuel affect the range of an aircraft?

A

Yes. Higher specific gravity means greater range for a given volume of fuel.

20
Q

Does the temperature of the fuel affect its calorific value?

A

No.

21
Q

Before refueling (pressure) how should the aircraft and tanker/bowser be bonded?

A

The aircraft and tanker should first be bonded to earth then to each other.

22
Q

When an aircraft is parked for a prolonged period, how is condensation formation in the fuel tank minimised?

A

By leaving the tanks as full as possible?

23
Q

Why are fuel temperatures monitored in cruise flight?

A

Because if the fuel is allowed to get too cold, ice may form in the fuel and the fuel may freeze (become waxy).

24
Q

Why should turbine fuel not be allowed to drop below specified minimum temperature limits?

A

To reduce the possibility of ice crystals forming in the fuel or of the fuel freezing (become waxy).

25
Q

What is the freezing point of Jet A1 (JP5)?

A

-47°C

26
Q

What is the freezing point of Jet A (JP4)?

A

-40°C

27
Q

Why is a fuel heater (heat exchanger) part of a turbin engine’s fuel system?

A

To prevent ice crystal formation in the fuel.

28
Q

What do fuel heaters/heat exchangers use to raise the temperature of fuel?

A

Usually engine or gearbox oil, sometimes hydraulic fluid and occasionally bleed air.

29
Q

What would be the function of a hydraulic fluid (or engine oil ) heat exchanger located in a fuel tank?

A

To cool the hydraulic fluid/engine oil and to warm the fuel.

30
Q

Why is AVTUR given an upper temperature limit?

A

To ensure the fuel does not boil ( vapor release/lock)

31
Q

What is the function of the fuel boost (auxiliary) pump?

A

To provide fuel under pressure to the inlet side of the main fuel pump.

32
Q

Where are the fuel boost (auxiliary) pumps usually located?

A

In the fuel tanks

33
Q

What type pump is usually used for the fuel boost pumps?

A

Electrically driven gear or impeller type pumps.

34
Q

What is the effect of a fuel tank’s boost (auxiliary) pump(s) failing?

A

To main pump sucks the fuel out of the tanks

35
Q

What is the function of the fuel jettison (dump) system?

A

To reduce the fuel quantity and therefore aircraft weight in the even t of an emergency landing.

36
Q

During fuel jettisoning, what feature protects against the inadvertent dumping of all the fuel?

A

Automatic jettison system shutoff and standpipes in the tanks.

37
Q

What is the function of the fuel filter bypass valve?

A

To ensure that fuel flow is not impeded if the filter becomes blocked.

38
Q

What is the function of a fuel flow meter system?

A

To measure the rate fuel is being used by the engine.

39
Q

Where is the fuel flow transmitter located in the fuel system?

A

At the outlet of the fuel control/metering unit.

40
Q

What is the purpose of the bypass system in the high pressure filter of a turbine engines fuel system?

A

To open and allow continued fuel flow if the filter becomes blocked.

41
Q

What limiting functions does the FCU perform?

A

Limits the turbine outlet temperature and fan speeds.

42
Q

What is basic function of an electronic engine control (EEC)?

A

To schedule (trim/find tune/adjust) the fuel flow to the engine under all conditions.

43
Q

What method is used to reduce combustion temperature without reducing mass flow of the gases?

A

To trim the fuel /air ratio as lean as possible.

44
Q

What is the function of the air shroud on an atomiser type (duplex) fuel spray nozzle?

A

To cool the nozzle and to reduce the formation of carbon deposits around the tip of the nozzle.

45
Q

What is the function of the dump valve on engine shutdown?

A

To allow fuel in the manifold to drain away.

NZCAA BGT Exam (16 decks)

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