Definition
A pump used to remove water that has collected in the lowest interior compartment of a seaplane or amphibian's hull or float. The bilge is the lowest internal section where any water that leaks past the hull or seals naturally pools, and the bilge pump clears it out before the accumulated weight affects buoyancy, balance, or performance.
Plain English
A pump that removes water from the bottom of a seaplane's hull or float, where leaking water tends to collect.
Context Anchor
Seen during seaplane and floatplane preflight checks, after docking, or anytime water may have entered a hull or float.
Derivation
Bilge comes from an old nautical term for the rounded lower part of a ship's hull, where water naturally collects. The same word and the same idea were carried over to seaplanes, since a float or hull on the water has the same problem a boat does.
Why Pilots Care
Removing accumulated water prevents added weight, corrosion, and loss of buoyancy that could compromise takeoff or safety.
Intuition Check
A bilge pump is not a fuel pump or an engine oil pump. In this context, it is for removing water from the lowest part of a seaplane hull or float.
Example Sentence 1
Before the first flight of the day, the pilot used the bilge pump to clear water that had seeped into each float overnight.
Example Sentence 2
During the preflight, she checked that the bilge pump worked before the seaplane flight.