Module 11A.10 — Fuel systems (ATA 28) and inerting (ATA 47)

Levels

All parts of 11.10 are level 1 for A1 and level 3 for B1.1: system layout, tanks, supply, cross-feed/transfer, refuel/defuel, indication and warnings, dumping/venting/draining, inert gas systems (ATA 47) and longitudinal balance (CG) fuel systems.

Fuels

Fuel	Key properties
Jet A-1	Kerosene; freezing point −47 °C max; flash point 38 °C min; standard outside North America
Jet A	As Jet A-1 but freezing point −40 °C (mainly USA)
Jet B / JP-4	Wide-cut (kerosene + naphtha), lower flash point, higher fire risk; cold-climate use
AVGAS 100LL	Piston fuel, dyed blue (see 11B/11C)

• Additives: anti-icing (FSII), anti-static, anti-oxidant, corrosion inhibitor, biocides.
• Contamination: water (free, entrained, dissolved), solids, microbial growth (fungi/bacteria at the fuel/water interface — black sludge, corrosion of integral tanks), and mis-fuelling.
• Fuel density varies with temperature (~0.78–0.84 kg/L for Jet A-1); quantity is measured as mass.

11.10(a) System layout, tanks and supply

Tanks

Type	Features
Integral (wet wing)	Sealed wing structure; ribs act as baffles; baffle check valves keep fuel near pumps; access panels on lower skin
Centre tank	In the wing centre box; on many types it is used first; heat from adjacent packs raises flammability → inerting
Bladder (bag) tanks	Flexible tanks in cavities (some business jets, helicopters)
Rigid removable	Light aircraft
Surge (vent) tanks	At wing tips; catch fuel from vents and return it
Trim tank	In the horizontal stabiliser on some long-range types — see 11.10(e)
Auxiliary tanks	In cargo holds on some aircraft

Supply to engines

• Booster pumps: AC electric centrifugal pumps, two per main tank (redundancy), in canisters so they can be changed without draining; pressure switches for low-pressure warnings.
• Ejector (jet) pumps: motive flow from the booster pump or engine supply entrains fuel from tank corners/scavenge areas — no moving parts.
• Suction feed: if boost pumps fail, engine-driven pumps can suck fuel through a bypass valve — altitude limits apply (dissolved air, vapour lock).
• LP (spar) valve / fire shut-off valve: closes fuel to the engine (pulling the fire handle or engine master switch).
• Engine-driven pumps and fuel heaters/filters (see Module 15).