Fuel Systems
Crash-resistant (self-sealing) tanks and breakaway couplings, boost pumps and crossfeed, and capacitance quantity.
Fuel systems — summary notes
Free- Fuel is held in tanks (often CRASH-RESISTANT, self-sealing bladder tanks with breakaway couplings to prevent post-crash fire); boost pumps deliver fuel under positive pressure to the engine(s).
- A crossfeed lets either engine draw from either tank on twins; tanks are vented, have water drains at their low points, and fuel is filtered.
- Fuel QUANTITY is measured by capacitance probes; fuel flow, pressure and low-level/low-pressure warnings are provided.
- Crash-resistant fuel systems (CRFS) — flexible bladder cells, self-sealing breakaway valves and frangible fittings — are a major helicopter safety feature to prevent fuel-fed fires in a survivable crash.
- Refuel/defuel and bonding/earthing for static control follow the same rules as fixed-wing.
- ⚠ Exam trap: helicopters emphasise CRASH-RESISTANT fuel systems (self-sealing bladder tanks + breakaway couplings) to prevent post-impact fire; fuel quantity is by capacitance probes, and crossfeed balances a twin.
What features make a helicopter fuel system 'crash-resistant', and why does it matter?
A crash-resistant fuel system uses flexible, self-sealing bladder tanks that resist tearing, plus breakaway (frangible) couplings and self-sealing valves at every connection so lines separate cleanly and seal rather than spilling fuel. This prevents fuel spraying onto hot or sparking components in an otherwise-survivable crash, dramatically reducing the risk of a post-impact fire — historically a major cause of helicopter accident fatalities.
Fuel systems concept map
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Fuel systems quiz
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