11.10 Fuel Systems

Question 1

What does a fuel system usually consist of?

Answer 1

Tanks, pumps, filters, valves, lines and metering and monitoring devices.

Question 2

What are rigid fuel lines made of?

Answer 2

Steel or aluminium alloy

Question 3

What are the two basic types of fuel?

Answer 3

Reciprocating fuel (avgas)
Turbine fuel (Jet fuel)

Question 4

How is AVGAS made?

Answer 4

Hydrocarbon compound refined from crude oil by a process called fractional distillation.

Question 5

How is AVGAS different to jet fuel?

Answer 5

It is really volatile and extremely flammable with a low flash point.

Question 6

What types of jet fuel are there?

Answer 6

Jet A1
Jet A
Jet B

Question 7

What is the flashpoint of Jet A and A1?

Answer 7

43 to 65 degrees c

Question 8

Which is better at the lower temp, A1 or A?

Answer 8

A1

Question 9

What is the density of A1 and A at 15 degrees c?

Answer 9

0.81kg/litre

Question 10

What three types of fuel tank are there?

Answer 10

Rigid removable
Bladder
Integral

Question 11

What were many early fuel tanks made of?

Answer 11

Terneplate, a thin sheet of steel coated in lead or tin alloy.

Question 12

What is a wet wing?

Answer 12

Integral tank design

Question 13

What does NGS stand for?

Answer 13

Nitrogen generating system

Question 14

What does the NGS do?

Answer 14

Designed to improve safety by reducing the risk of fuel tank explosions in aircraft. It does this by replacing oxygen in the fuel tanks with nitrogen

Question 15

How does the NGS get nitrogen?

Answer 15

Extracted from the bleed air.

Question 16

What four classifications of fuel leak are there?

Answer 16

Leak
Seep
Heavy seep
Running leak

Question 17

How long is needed to monitor a leak?

Answer 17

30 mins

Question 18

What area is classed as a stain?

Answer 18

19mm diameter

Question 19

What area is classified as a seep?

Answer 19

19-38mm diameter

Question 20

What area is a heavy seep?

Answer 20

38-101mm

Question 21

What is SFAR 88?

Answer 21

Manages the safety, inspection and procedures of the fuel system and its components.

Question 22

What is CDCCL?

Answer 22

Critical design control configuration limitations.

Question 23

What does CDCCL control?

Answer 23

Refers to a feature of the fuel system design, for which integrity must be maintained to ensure that unsafe conditions do not develop.

Question 24

What kind of components may you find as part of CDCCL?

Answer 24

Bonding leads
Harnesses and probes
Pumps
Access panels

Question 25

Are CDCCL's mandatory and how can they be changed?

Answer 25

Yes, only with approval from the NAA

Question 26

What must the concentration of fuel vapours be kept below?

Answer 26

The lower explosive limit.

Question 27

What is FQIS?

Answer 27

Fuel Quantity Indicating System

Question 28

What four options does the selector valve have in a gravity feed system?

Answer 28

Shut off to the engine Feed from the right wing Feed from the left wing Feed from both wings

Question 29

What are large aircraft fuel systems split into?

Answer 29

Storage Vent Distribution Feed Indicating

Question 30

What is a wobble pump?

Answer 30

Old school hand operated pump that delivers fuel backing up the engine driven pump.

Question 31

What is the disadvantage of a wobble pump?

Answer 31

It requires fuel lines to be run through the flight deck.

Question 32

How do vane type pumps regulate flow?

Answer 32

Adjustable pressure relief component

Question 33

Centrifugal pumps are normally in the tank, what do they need if they are outside the tank?

Answer 33

Removal valve so that the pump can be removed without draining the fuel.

Question 34

Depending on aircraft design what is the centrifugal boost pump used for?

Answer 34

EDP

Question 35

What are fuel pumps cooled by?

Answer 35

The fuel flow

Question 36

What do flapper valves allow?

Answer 36

Allow fuel to flow inboard to the pump.

Question 37

What does an ejector pump do?

Answer 37

Ensure the pump always has liquid fuel at the inlet.

Question 38

What is installed between the supply tanks and the engine fuel system to protect the engine-driven fuel pump and various control devices?

Answer 38

Low pressure filter

Question 39

What are the three most common types of fuel filter?

Answer 39

Micron Wafer screen Plain screen

Question 40

What size particles can a micron filter remove?

Answer 40

10-25 microns

Question 41

What is the downside of micron filters?

Answer 41

They are easily clogged therefore a bypass is required.

Question 42

What are the two weight limits that must not be exceeded?

Answer 42

Max take off Max structural landing weight

Question 43

What are fuel vent systems designed to do?

Answer 43

Relieve pressure in the fuel tanks and to allow proper flow of fuel.

Question 44

What does the vent system maintain the pressure at?

Answer 44

Atmospheric

Question 45

What can under pressurisation of the fuel tanks cause?

Answer 45

Component malfunction and engine fuel starvation.

Question 46

What does not happen in an inflight fuel transfer?

Answer 46

Fuel is not moved from one tank to another, instead it is used to feed the engine until the levels are corrected.

Question 47

For a ground fuel transfer what must the engineer do?

Answer 47

-Open the x feed valves -Switch on boost pumps in tank which fuel is leaving -Open defuel valve -Open refuel valve for tank that is receiving

Question 48

In a ground fuel transfer what does opening the defuel valve achieve?

Answer 48

Connects the engine feed manifold to the refuel manifold.

Question 49

Fuel cross feed valves are motor actuated, what main parts do they have?

Answer 49

Valve body Adapter and shaft Actuator

Question 50

What is the actuator in the fuel x feed valve?

Answer 50

28V DC

Question 51

How many fuel flow indicators are there?

Answer 51

One per engine

Question 52

Where is the temp sensor usually located?

Answer 52

Main fuel tank

Question 53

Where are low pressure sensors located?

Answer 53

Boost pump inlet lines

Question 54

What is a ratiometer type fuel quantity sensor?

Answer 54

The most common, uses a DC loop which utilises variable resistance to drive the indicator.

Question 55

How do capacitance type fuel quantity sensors work?

Answer 55

Wired in parallel, as the level changes so does the capacitance of each one. A computer then sums the individual capcitances.

Question 56

What is used to match the capacitance output with the pre calibrated indicator?

Answer 56

A trimmer

Question 57

The amount of electricity stored in a capacitor depends on what 3 things?

Answer 57

Area of the plates Distance between the plates Dielectric constant

Question 58

What is meant by the ullage?

Answer 58

Emptiness of the tank

Question 59

What calculations does an ultrasonic fuel quantity system use?

Answer 59

Fillage = Total height - ullage

Question 60

Valve in transit lights have what lighting states to indicate position?

Answer 60

Abnormal condition- Dim Transit- bright Normal- off

Question 61

What two methods of refuelling are there?

Answer 61

Gravity overwing Pressure

Question 62

What are the main components of a typical refuelling system?

Answer 62

Couplings Valves Manifold Diffusers

Question 63

What three modes of pressure refuelling are there?

Answer 63

Manual Automatic Override

Question 64

What is key before refuelling in manual mode?

Answer 64

Calculate the distribution

Question 65

What pressure is pressure defuelling?

Answer 65

25 psi to 50psi

Question 66

When will the FCMC start an aft transfer?

Answer 66

Landing gear and slats retracted Trim tank not full Inner tank above 6250kg

Question 67

When will the aircraft do an automatic fuel transfer forward?

Answer 67

CG equals target Inner tank less than 4000kg