I am curious if the inverted plane in the movie Flight 2012 has anything to do with reality / emergency practices. And if it does, can you please explain the concept/ aerodynamics behind of it , or why someone would ever do that even as last resort?
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2 Answers
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In the movie Flight (2012), Captain Whittaker (Denzel Washington) does not explain why he deliberately inverted his aircraft, but the obvious inference is: since the horizontal stabilizer has slipped off its jackscrew and become jammed into a descent angle beyond the authority of the elevators to correct, in inverted flight this would push the nose far above the horizon and result in either a climb or a stall.
In this attitude, Whittaker would have been pulling back on the yoke to prevent the stall. In the movie, this worked. The aircraft was still not under control, but was no longer diving and overspeeding. Suddenly rolling the aircraft upright in the last seconds before contact with terrain is the unrealistic part. A hot fighter jet might accomplish this but the roll rate of a passenger jet is too slow.
The movie's flight emergency is based mostly on the crash of Alaska Airlines flight 261 on January 31, 2000. In that incident, the pilots experienced a jammed horizontal stabilizer with uncontrollable dive, and inverted their MD-80 to arrest their descent. Unfortunately in real life neither flying officer was stuffed to the gills with booze and coke: the maneouver failed and the aircraft crashed with no survivors.
answered Jan 19, 2014 at 1:33
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2$\begingroup$ @Breveleri a jammed horizontal stabilizer does not leave you with many options? but coke and booze helps?:) $\endgroup$– blendedCommented Jan 19, 2014 at 12:29
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10$\begingroup$ Indeed. An important plot point of the movie is that a clean and sober pilot would never have attempted such an insane stunt. $\endgroup$ Commented Jan 19, 2014 at 15:43
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2$\begingroup$ It would also be worth mentioning that in real life the fuel feed lines are designed to have gravity in a specific direction. In the Alaska 261 case the engines started spooling down shortly after the inverted position was achieved (see final report) $\endgroup$– FedericoCommented Apr 25, 2016 at 12:37
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FedEx 705 underwent extreme maneuvers, even inverted flight. The captain was trying to disorient a hijacker while the first officer fought him hand-to-hand.
Here's a dramatization of it. Not sure if it's the best one but there are others.
Most of your airfoils are designed to produce lift at 0 angle of attack (a perfectly symmetrical airfoil will not), which means that although it's more difficult than with a symmetrical airfoil, you can fly (inverted) at an angle that they will produce lift at negative angles as well. You will be inverted with the nose very high above the horizon, higher than it would be for level flight at a normal attitude.
Beyond that, the aircraft is really not built to do invert maneuvers. Legally they must be able to withstand -1G, but that doesn't leave much room to maneuver while inverted. In reality, most aircraft are designed beyond legal limits just for safety. On top of that, just because an aircraft is rated for a certain load limit does not mean that it will catastrophically fail if that limit is exceeded. It may bend and wrinkle beyond repair, but it should take a lot more than that to fall apart. The problem is that you have no guarantee.
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6$\begingroup$ A barrel roll is a 1G maneuver, it doesn't put any unnatural stress on the airframe if done correctly. FedEx 705 didn't do a barrel roll -at least not a coordinated one- he was inverted. $\endgroup$ Commented Jan 18, 2014 at 21:48
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3$\begingroup$ Then flight movie i guess is just... movie:) $\endgroup$– blendedCommented Jan 18, 2014 at 21:56
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3$\begingroup$ I would add that Airbus A320 and all later models, Boeing 777 and 787 and some other aircraft won't let you invert them, because their control computer limits pitch and roll. $\endgroup$ Commented Jan 18, 2014 at 22:44
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5$\begingroup$ @JanHudec yeah, talk about taking the fun out of airliner aerobatics ;-) $\endgroup$ Commented Jan 20, 2014 at 10:49
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2$\begingroup$ Apart from aerodynamics and strength, there are other systems considerations, most notably fuel. The fuel system of most non-aerobatic aircraft is not designed for negative G forces (notwithstanding the fuel pumps etc.) While it will often allow brief excursions to that territory, sustained inverted flight will likely result in fuel starvation or at least unstable fuel supply. $\endgroup$– ZeusCommented Feb 23, 2016 at 7:01