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I'm not even close to an aviation enthusiast, but after watching some videos I found I have a deep misunderstanding on how airplanes work.

airplane image showing engine producing thrust and pushing the plane forwards.

I've seen many cases where one of the engines fail and the plane has to fly on a single engine for a long time.

How doesn't the fact that the forces are now uneven drive the airplane to a side drift? (I'm sure this is all wrong, but I just don't understand how)

Délisson Junio
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    Note that the engine force arrows should be pointing the other way. –  Jun 19 '18 at 10:58
  • @ymb1: Unless that plane's had a double engine failure, in which case the arrows are the right way around for the force generated by those giant windmilling drag buckets. – Vikki May 29 '19 at 01:07
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    @Sean: Indeed –  May 29 '19 at 01:08

1 Answers1

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It does. Asymmetric thrust will in fact force the airplane into a turn unless the pilot counteracts this by using rudder and aileron to command an equal turn force in the other direction. Typically both opposing rudder, and banking away from the dead engine will be used to result in straight (although uncoordinated) flight.

Skip Miller
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  • oh, so I was right? I watched a video about Air Transat 236, and it didn't explained that. thanks. – Délisson Junio May 24 '14 at 21:28
  • Well, from 06:13 until 06:26, the plane was flying with one engine providing thrust. During those few minutes, the pilot would have had to do as Skip suggests. After 06:26, the second engine died due to fuel starvation and the airliner was then a glider. – CGCampbell May 25 '14 at 00:35
  • @wingleader: The interesting part of that incident was when both engines failed. One engine failing happens all the time and is not serious trouble (unless there is a secondary damage) so they would not consider that phase worthy of detailed discussion. – Jan Hudec May 25 '14 at 01:02
  • @Jan One engine failing happens all the time? you couldn't scare me less ): – Délisson Junio May 25 '14 at 04:19
  • Jan has a point: See the Aviation Herald website for all kinds of events in aviation (http://avherald.com). The last plane with engine trouble was a 767-300 on May 22nd. Given the number of flights per day worldwide, the probability for a single airplane is rare, indeed. – Peter Kämpf May 25 '14 at 06:28
  • Is an engine failing ever the kind of thing that can go unnoticed by the passengers, so that it could conceivably have happened to me? Or is it inevitably "we are sorry to announce that we're immediately diverting to the nearest airfield large enough to land, please try not to panic"? – Steve Jessop May 25 '14 at 10:13
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    Passengers would very likely notice. There'd be a change in sound, and the pilot would have to "feel around" for the right balance of controls to compensate for the asymmetrical thrust. And, yes, I'd expect a divert to the nearest suitable airfield if the plane wasn't very close to its original destination. – Russell Borogove May 25 '14 at 15:33
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    @wingleader: All aircraft that carry more than 12 passengers must be able to fly with one engine inoperative (tested during certification) and pilots train it at least twice a year in simulator. There is really no immediate danger in such incidents (unless it's uncontained failure with secondary damage, but even Quantas 32, which was rather serious uncontained failure, flew for another almost 2 hours and safely landed). – Jan Hudec May 25 '14 at 19:54
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    @RussellBorogove: In 2-engine aircraft, it is always emergency (there is no danger yet, but there is no redundancy any more) and land at nearest suitable airport. In 4-engine aircraft the flight may be continued if there is enough fuel and no risk of further damage (usually when the engine was shut down manually because of indications outside limits rather than quit itself). Then it's up to discussion with dispatch. – Jan Hudec May 25 '14 at 19:58
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    @JanHudec: just for posterity because I have this discussion all the time: per definition, an engine failure in a perf class A is an urgency (pan-pan) not an emergency (mayday). – Radu094 Mar 20 '15 at 21:08
  • As a pilot, I really don't care if I have 10 engines on my aircraft. If one fails, it happened for a reason. And that reason can make the next one fail too. In my opinion, it's irresponsible of a pilot to continue flying after a failed engine - especially one that can't be restarted. It may not be an emergency (though I don't know how it's not), but it's darn sure urgent enough to head to my nearest alternate. As the Pilot In Command, I'd always prefer the safe decision. And I wouldn't say that it "happens all the time". – Shawn Mar 20 '15 at 21:55
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    @Radu094 and what happens when your HYD pump on the good motor decides to quit? Engines do a whole lot more than just provide thrusties; in fact, I'm much more concerned with the accessories I might have just lost with an engine failure, vice the actual engine itself. – Rhino Driver Mar 21 '15 at 16:15
  • It doesn't matter: Calling it a mayday instead of pan-pan is at the captain's discretion, but technically a mayday implies you are no longer capable of sustained flight and are crashing. This stuff should've been taught in Radio Comms classes for PPL – Radu094 Mar 21 '15 at 16:57
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    @Radu094: Mayday implies there is an imminent danger to the flight. It does not necessarily mean it's not capable of sustained flight at all. – Jan Hudec Mar 23 '15 at 07:08
  • @JanHudec: incapable of sustained flight is maybe stretching it a bit , but "imminent danger and requiring immediate assistance" usually means just that in aviation. In fact, you will have to work hard to argue the "imminent and immediate" requirement in an aircraft still capable of flight ( ahem and not on fire). Maybe this belongs in a chat... – Radu094 Mar 23 '15 at 19:16
  • @RussellBorogove: And even then, they'd still be going to the nearest suitable airport - it's just that the nearest suitable airport happens to also be the original destination. – Vikki May 29 '19 at 01:05