Turbine Engine Fuel Systems Flashcards
How does the volatility of AVTUR compare to that of AVGAS?
The volatility of AVTUR is lower.
How does the calorific value of AVTUR compare to that of AVGAS?
The calorific value of AVTUR is higher.
How does the specific gravity of AVTUR compare to that of AVGAS?
The specific gravity of AVTUR is higher.
How does AVTUR’s propensity for absorbing water compare to that of AVGAS?
AVTUR has a higher propensity for absorbing water.
AVTUR holds significantly more water in suspension.
How does the flashpoint of AVTUR compare to that of AVGAS?
The flashpoint of AVTUR is higher.
What safety devices are used to prevent inadvertent selection of the wrong fuel?
Different color dyes added to the fuel.
The AVTUR delivery nozzle is too large to fit into an AVGAS tank.
By what names is turbine fuel known?
AVTUR; Jet A/ Jet A1; JP4/JP5; or F40/F35.
What is the difference between Jet A/ Jet A1 and JP4/ JP5?
In the United States, Jet A is often called JP4 and Jet A1 is often called JP5
Are turbine fuels required to have lubricating properties?
Yes
If alternative/emergency fuels are approved for use in an aircraft, in which document would this be specified?
In the aircraft flight manual.
Why is water contamination more of a problem in AVTUR than in AVGAS?
Water contamination is more of a problem in AVTUR than in AVGAS because AVTUR can hold significantly more water in suspension than can AVGAS.
How is water tested for in turbine fuel?
A chemical water check is carried out, where a tester changes color if an excessive amount of water is present in the fuel sample.
What are the common additives put into AVTUR?
Anti-icing and anti-microbiocidal additives are often added to AVTUR.
What is the ideal air to fuel ratio for combustion in a turbine engine?
The ideal (stochiometric) air to fuel ratio is 15:1.
When refueling, why is the fuel’s density measured and recorded?
To enable an accurate fuel weight to be calculated for the volume loaded.
Why is knowledge of fuel’s specific gravity (SG) relevant when refueling an aircraft?
Loading is in volume (liters or gallons), and to convert volume to weight (mass) the SG is required.
What is the specific gravity (SG) of Jet A1 at 15 °C?
Approx 0.8 kgs per liter (0.8 grams per mililitre )
Does the temperature of the fuel affect its specific gravity?
Yes, The relationship inversely proportional. That is, if the temperature increases the specific gravity reduces.
Does the specific gravity of a fuel affect the range of an aircraft?
Yes. Higher specific gravity means greater range for a given volume of fuel.
Does the temperature of the fuel affect its calorific value?
No.
Before refueling (pressure) how should the aircraft and tanker/bowser be bonded?
The aircraft and tanker should first be bonded to earth then to each other.
When an aircraft is parked for a prolonged period, how is condensation formation in the fuel tank minimised?
By leaving the tanks as full as possible?
Why are fuel temperatures monitored in cruise flight?
Because if the fuel is allowed to get too cold, ice may form in the fuel and the fuel may freeze (become waxy).
Why should turbine fuel not be allowed to drop below specified minimum temperature limits?
To reduce the possibility of ice crystals forming in the fuel or of the fuel freezing (become waxy).
What is the freezing point of Jet A1 (JP5)?
-47°C
What is the freezing point of Jet A (JP4)?
-40°C
Why is a fuel heater (heat exchanger) part of a turbin engine’s fuel system?
To prevent ice crystal formation in the fuel.
What do fuel heaters/heat exchangers use to raise the temperature of fuel?
Usually engine or gearbox oil, sometimes hydraulic fluid and occasionally bleed air.
What would be the function of a hydraulic fluid (or engine oil ) heat exchanger located in a fuel tank?
To cool the hydraulic fluid/engine oil and to warm the fuel.
Why is AVTUR given an upper temperature limit?
To ensure the fuel does not boil ( vapor release/lock)
What is the function of the fuel boost (auxiliary) pump?
To provide fuel under pressure to the inlet side of the main fuel pump.
Where are the fuel boost (auxiliary) pumps usually located?
In the fuel tanks
What type pump is usually used for the fuel boost pumps?
Electrically driven gear or impeller type pumps.
What is the effect of a fuel tank’s boost (auxiliary) pump(s) failing?
To main pump sucks the fuel out of the tanks
What is the function of the fuel jettison (dump) system?
To reduce the fuel quantity and therefore aircraft weight in the even t of an emergency landing.
During fuel jettisoning, what feature protects against the inadvertent dumping of all the fuel?
Automatic jettison system shutoff and standpipes in the tanks.
What is the function of the fuel filter bypass valve?
To ensure that fuel flow is not impeded if the filter becomes blocked.
What is the function of a fuel flow meter system?
To measure the rate fuel is being used by the engine.
Where is the fuel flow transmitter located in the fuel system?
At the outlet of the fuel control/metering unit.
What is the purpose of the bypass system in the high pressure filter of a turbine engines fuel system?
To open and allow continued fuel flow if the filter becomes blocked.
What limiting functions does the FCU perform?
Limits the turbine outlet temperature and fan speeds.
What is basic function of an electronic engine control (EEC)?
To schedule (trim/find tune/adjust) the fuel flow to the engine under all conditions.
What method is used to reduce combustion temperature without reducing mass flow of the gases?
To trim the fuel /air ratio as lean as possible.
What is the function of the air shroud on an atomiser type (duplex) fuel spray nozzle?
To cool the nozzle and to reduce the formation of carbon deposits around the tip of the nozzle.
What is the function of the dump valve on engine shutdown?
To allow fuel in the manifold to drain away.
