Definition
A flight instrument, typically a magnetic compass, that is sealed and constructed so that the internal damping fluid will not leak or splash out regardless of aircraft attitude. The sealed design allows the instrument to remain readable and serviceable through steep banks, climbs, descents, inverted flight, or aerobatic maneuvers without losing fluid or developing bubbles that would impair its function.
Plain English
An instrument built so that the liquid inside it cannot spill out, no matter what position the aircraft ends up in.
Context Anchor
Seen in unusual-attitude recovery discussions, where the pilot must know which instruments can still be trusted after the airplane has been placed in an extreme attitude.
Derivation
From 'non-' (not) + 'spillable' (able to be spilled). The name simply describes what the instrument cannot do: spill its fluid. Knowing the instrument is fluid-filled (and that the fluid normally could spill in a non-sealed design) explains why this feature matters.
Why Pilots Care
Keeps critical attitude or turn information available when the aircraft is in an unusual attitude, supporting safe and timely recovery.
Intuition Check
Do not read “nonspillable” as meaning only that the instrument cannot leak fluid. In this context, it means the instrument is designed not to lose its correct indication when the airplane is put into an extreme attitude.
Example Sentence 1
Aircraft certified for aerobatic flight are typically fitted with a nonspillable-type instrument in place of the standard magnetic compass.
Example Sentence 2
Preflight inspection confirmed that all nonspillable-type instruments showed no fluid leakage or damage.