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?
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.
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.