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Phugoid
In aviation, a phugoid or fugoid (/ˈfjuːɡɔɪd/ ⓘ) is an aircraft motion in which the vehicle pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes "downhill" and "uphill". This is one of the basic flight dynamics modes of an aircraft (others include short period, roll subsidence, dutch roll, and spiral divergence).
In the 1975 Tan Son Nhut C-5 accident, USAF C-5 68-0218 with flight controls damaged by failure of the rear cargo/pressure door, encountered phugoid oscillations while the crew was attempting a return to base and crash-landed in a rice paddy adjacent to the airport. Chesley "Sully" Sullenberger, Captain of US Airways Flight 1549 that ditched in the Hudson River on January 15, 2009, said in a Google talk that the landing could have been less violent had the anti-phugoid software installed on the Airbus A320-214 not prevented him from manually getting maximum lift during the four seconds before water impact. Retrieved 6 July 2022.^ Frederick William Lanchester, Aerodonetics: Constituting the second volume of a complete work on aerial flight, (London, England: Archibald Constant Co. Ltd., 1908), p. viii and p. 348.^ Ranter, Harro.
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