13.13 and 13.14 Fuel systems (ATA 28/47) and hydraulic power (ATA 29) for B2

Scope

B2 and B2L Airframe Systems rating.

• 13.13 Fuel: (a) system layout, tanks, supply — level 1; (b) fuel handling, cross-feed, transfer, refuel/defuel — level 2; (c) indications and warnings — level 3; (d) special systems: dumping, venting, draining, inert gas systems — level 1; (e) longitudinal balance (CG) fuel systems — level 3.
• 13.14 Hydraulics: (a) layout, fluids, reservoirs, accumulators, filters, distribution — level 1; (b) pressure generation electric/mechanical, pressure control, indication and warning, servicing — level 3; (c) pneumatic pressure generation, emergency generation, interfaces — level 3.

The B2 emphasis is on sensors, indication, control logic and electrical interfaces.

Fuel system layout

• Integral tanks (sealed wing structure), centre tank, sometimes trim tank in the horizontal stabiliser and additional centre tanks; surge/vent tanks at the wing tips.
• Boost pumps (AC motor-driven, two per tank) supply the engines; override/jettison pumps in the centre tank have higher output pressure so centre fuel is used first.
• Engine LP shut-off (spar) valves, cross-feed valves, transfer valves, APU fuel feed with its own DC pump.
• Suction feed (gravity/engine pump suction) is available if boost pumps fail, with altitude limits.
• Pumps are often cartridge-type, removable without draining the tank (canister with check valve).

Fuel handling

• Pressure refuelling through underwing couplings to a refuel gallery; refuel valves controlled by a refuel panel/computer that closes each tank's valve at the preselected quantity or at high-level sensors (overfill protection).
• Defuelling by suction via the refuel coupling or by the boost pumps; transfer between tanks on the ground.
• Cross-feed connects left and right feed systems — used to correct fuel imbalance or for engine-out operation.