Definition
A flexible, reinforced rubber or synthetic fabric bag installed inside an aircraft structural cavity to hold fuel. The bladder is fitted into a prepared compartment in the wing or fuselage and secured with snaps, lacing, or fittings. The surrounding aircraft structure carries the loads; the bladder simply contains the fuel and prevents leakage.
Plain English
A tough, flexible bag that sits inside the wing or fuselage and holds the aircraft's fuel. The aircraft structure around it provides the strength; the bag just keeps the fuel in.
Context Anchor
Seen in aircraft fuel system descriptions, maintenance records, and inspections for fuel leaks, damage, or replacement.
Derivation
‘Bladder’ comes from the Old English blædre, meaning a flexible sac that holds liquid (as in the human bladder). The name fits because the fuel cell is exactly that — a flexible sac shaped to fit a cavity and hold liquid.
Why Pilots Care
These cells reduce leak risks from corrosion and allow fuel to be carried in irregular spaces, directly affecting flight safety and range.
Analogy
Similar to a durable camping water bladder, but engineered to safely contain aviation fuel inside the wing.
Intuition Check
A bladder-type fuel cell is not an electrical fuel cell that makes power. In this context, “fuel cell” means a tank or chamber that stores fuel, and “bladder-type” means it is flexible rather than rigid.
Example Sentence 1
The mechanic drained the wing and removed the bladder-type fuel cell through the access panel to repair a small leak at one of the fittings.
Example Sentence 2
Many older aircraft rely on bladder-type fuel cells to fit maximum fuel volume within the wing ribs.