called a weight-on-wheels switch signals the lift dumpers to be raised. The flight control spoilers are also raised as additional lift dumpers. Virtually all modern jet aircraft are fitted with lift dumpers. The British Aerospace 146 is fitted with particularly wide-span spoilers to generate additional drag and make reverse thrust unnecessary. A number of accidents have been caused either by inadvertently deploying lift dumpers on landing approach, or forgetting to set them to 'automatic'. Incidents and accidents Air Canada Flight 621 – Premature deployment of the spoilers at low altitude contributed to this crash in Toronto on 5 July 1970. United Airlines Flight 553 – Forgetting to deactivate the spoilers contributed to crash at Chicago Midway International Airport on 8 December 1972. Loftleiðir Icelandic Airlines Flight 509 – Deployment of lift dumpers while attempting to arm them 40 feet above the runway caused this accident at John F. Kennedy International Airport on 23 June 1973. American Airlines Flight 965 – Forgetting to deactivate the spoilers while climbing to avoid a mountain contributed to this crash on 20 December 1995. American Airlines Flight 1420 – Forgetting to deploy the spoilers contributed to this crash at Little Rock National Airport on 1 June 1999. Atlantic Airways Flight 670 – The spoilers did not deploy during landing on a fairly short wet runway, causing overrun and falling over a cliff, on 10 October 2006. TAM Airlines Flight 3054 – This Airbus A320's pilots were aware of their deactivated starboard engine #2 thrust reverser, and so apparently did not attempt to use it to brake when attempting to land at São Paulo's Congonhas Airport on 17 July 2007; under one theory of the cause, they used an old procedure, which reduced the required runway length for landing but was superseded because it invited pilot error, which required them to leave the engine in idle rather than reverse thrust, and mistakenly left the engine at full power. The plane's spoilers may have been their only method of braking at speed. The plane slid off the runway, over a major highway, and ploughed into a warehouse, killing all 186 on board as well as several on the ground. It was Brazil's worst aviation disaster. See also Air brake (aircraft) References Spoiler Aircraft wing components