Spoiler (aeronautics) - Lift Dumpers

Lift Dumpers

Lift dumpers are a special type of spoiler extending along most of the wing's length and designed to dump as much lift as possible on landing. Lift dumpers have only two positions, deployed and retracted, and must not be used in flight as they completely stall the aircraft.

Lift dumpers have three main functions:

• Preventing the aircraft 'bouncing' on the runway, a common problem with older airliners
• Providing greatly increased drag for slowing the aircraft
• Putting the weight of the aircraft on the wheels so that full braking may be immediate

Lift dumpers are almost always deployed automatically on touch down. The flight deck control has three positions: off, automatic ('armed'), and manual (rarely used). On landing approach 'automatic' is selected and at the moment of touchdown lift dumpers are deployed in a fraction of a second (flight spoilers will also be raised automatically).

Virtually all modern aircraft are fitted with lift dumpers. The Bae 146 was designed with particularly large full width lift dumpers providing sufficient drag to eliminate the need for thrust reversers.

A number of accidents have been caused either by inadvertently deploying lift dumpers on landing approach, or forgetting to set them to 'automatic'.