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In movies and television, commercial airliners that have lost electronics often go into flat spins and inevitably crash. Is this what would really happen? Would the plane be able to glide to a (possibly survivable) crash landing? Would it dive nose first into the ground? What would really happen?

In the past, some airplanes displayed an unrecoverable spin in which the nose was higher, relative to the horizon, than in conventional spins. This is sometimes called a flat spin, although whether a flat spin is indeed unrecoverable depends on aircraft type and loading. The plane spins on its belly around the normal axis.
Source

Revolution - Trailer (0:40/4:21)

  • Please give some examples of such movies. I don't think you mean "flat spin", and I am not sure this is notable. – Oddthinking Sep 19 '12 at 13:30
  • Revolution showed this in the first 3 minutes when "physics went crazy and no one knows why" – The Evil Greebo Sep 19 '12 at 13:40
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    No kidding. Perhaps that's why the question is being asked. – The Evil Greebo Sep 19 '12 at 14:06
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    Ah, I agree that that is a flat-spin; seemed an unusual rendering for a movie plane-crash. This is a special effect from a fantasy series. The claim isn't notable; no-one is expected to actually believe it. This is a question for scifi.stackexchange.com, not Skeptics.SE. – Oddthinking Sep 19 '12 at 15:02
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    @MichaelEdenfield gasoline engines use electricity to create the spark that ignites the gas, so they would stop if there was no electricity. Steam engines heat water by burning wood, coal, or other fuels, and require no electricity to run. – Tester101 Nov 13 '12 at 11:54
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I assume by "modern" you mean "fly by wire". The description creates an expectation that if "the electronics" go off, the plan can no longer fly and will be out of control (e.g. in a flat spin) until it crashes.

There are multiple levels of redundancy in flight critical avionics, and the degree of automation and "flight envelope protection" degrades in stages as specific pieces of equipment fail.

The Airbus system has 4 stages of electronic control modes ("laws" from "normal" through "alternate", "abnormal" and "direct" modes - basically the plane hands more and more control responsibility over to the pilot as things fail.

In any non-normal mode, it's possible to stall or fly the aircraft unsafely, but there's no expectation that the plane would be "out of control".

Most relevantly to the specific question, there is a 5th "mechanical backup" option, as shown by this description of the Airbus flight laws:

http://www.airbusdriver.net/airbus_fltlaws.htm

The mechanical backup provides for "temporary control" - it's quite unlikely that this would extend to making a safe landing - it wouldn't be possible to put the wheels down, for example, if there were no operating electronics.

Note that loss of all engines does not mean loss of all electricity - planes have a RAT (Ram Air Turbine) for emergencies - a wind-powered generator that pops out and basically turns the planes forward motion into electrical power.

Also, this argument is relevant for commercial passenger planes - for military aircraft, much greater risks are taken for the sake of speed and maneuverability, and fly by wire planes do fall out of the sky:

http://www.flightglobal.com/news/articles/fly-by-wire-failure-downed-indian-su-30mki-330051/

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    +1 for a more reality based answer. ;) The premise in this case, however, is one in which all electricity stops working, meaning even the RAT would fail to generate electricity needed to drive the servos and hydraulics to control the surfaces. – The Evil Greebo Sep 19 '12 at 13:49
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No, airplanes do not always crash from losing electronics.

Here is a real-life counter-example to the claim that losing electronics would cause a loss of control of the aircraft:

In 1998 a jet flew into hail, sustained damage to the electronics, and made a safe emergency landing in Chattanooga TN.

From the report at: http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20001211X10040&ntsbno=DCA98MA045&akey=1

"The flight crewmembers reported that as they proceeded through the gap, they observed an egg-sized piece of hail hit the center windshield, causing its outer pane to shatter. At the same time, they began experiencing turbulence that lasted about 10 seconds. They stated that approximately 1 to 2 seconds after the encounter with the first piece of hail, the airplane encountered significant hail, which lasted about 3 to 5 seconds and shattered the outer panes of the captain's and first officer's windshields. Both pilots stated that the hail caused significant damage to the skin of the airplane but that no control problems were noted. They stated the nose radome cover was torn off and that the noise level in the cockpit was high. They also stated that the airspeed indication was zero and the altimeter indications were erratic."

Erratic indicators show that the electronics was damaged. There was actually quite a bit of damage from this event.

DAMAGE TO AIRPLANE

The airplane's radome had separated and portions of it had been ingested into the right engine. All three outer panes of the cockpit front windshield were shattered. The wing leading edge devices, horizontal stabilizer leading edge, vertical stabilizer leading edge, and both left and right engine inlet cowls were dented and damaged. Both engines sustained foreign object damage.

But even this level of damage did not prevent a safe emergency landing with no fatalities.

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