My understanding of VTOL aircraft (correct me if I am mistaken) is that the plane accelerates vertically until it's a bit off the ground, at which point the thrust is slowly vectored horizontally, and when it's finished, the plane has enough speed to produce sufficient lift. So, what happens if an engine fails before the plane has enough speed to lift itself? I'm asking about both single and double engine planes, for example the F-35, Harrier Jump Jet, or Yak 36.

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    $\begingroup$ I would suggest ejection. Fast. $\endgroup$
    – vasin1987
    Commented Jan 24, 2018 at 17:51
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    $\begingroup$ What plane? This would be different for an F-35 or V-22. $\endgroup$
    – Ron Beyer
    Commented Jan 24, 2018 at 17:52
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    $\begingroup$ @RonBeyer I was thinking along the lines of a jet like the F-35. I'll add that to the question $\endgroup$
    – cat40
    Commented Jan 24, 2018 at 18:48
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    $\begingroup$ I wonder how much thought has been put into it when the airplane is designed. Ones like the Yak has independent engines front and aft and if one fails then the plane would certain just flip over instantly. Being military and especially Russian military pilots's lives is a resource, or even a consumable, so I imagine at the peak of cold war if they could save a reasonable chunk of time and money by increasing the pilot's death rate a littler they would probably do it. Just like what to do if the heat shield of space shuttle is damaged before reentry, the answer could be just "good luck" $\endgroup$ Commented Jan 24, 2018 at 19:16
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    $\begingroup$ Although not during takeoff, there's a video here of the correct procedure when a hover is messed up - youtube.com/watch?v=ax5w_4r7kCI --- note, "An RAF board of inquiry has now established that Flight Lieutenant Cann had accidentally operated the controls for throttle and nozzle direction lever at the same time causing it to drop like a stone." $\endgroup$
    – Party Ark
    Commented Jan 25, 2018 at 10:31

1 Answer 1


F35 and Harrier are both single engined. Both had a forward fan providing lift through this fan, and in case of Harrier forward nozzles turn aft for thrust. F35 it provided lift only. Aft nozzles in both types vector to give lift or thrust. In Harrier all nozzles are synchronised,

So silence from the engine means it's time for the black and yellow handle.. If a twin engine e VTOL aircraft where lift is provided by both engines and one has a failure, then again until you transition to sufficient aerodynamic lift you are going down... But also probably rolling away due to non symmetric thust. Look at design of DornierDo31. You can climb I side on at the Deutches Museum at Oberschleissheim near Munich.( I was Senior Systems Engineer on Harrier, Sea Harrier. )

  • $\begingroup$ The Yak-38 even had an automatic ejection if in the take-off mode it rolled over 60°—whether it was due to failure of one of the engines, sudden wind gust or incorrect handling, it was not recoverable either way and the pilot had to eject before the plane rolled over completely. $\endgroup$
    – Jan Hudec
    Commented May 13, 2020 at 6:13
  • $\begingroup$ Noted, makes sense, Harrie had nothing like that, F35. Harrie r did have pedal shakers to cue pilot to sideslip (press the rudder pedal to reduce) since a phenomenon called" intake momentum drag" at low speeds could cause yaw then roll divergence. It also has a yaw vane just ahead of the windshield to show pilot any sideslip. No associated sensor, just a "weathervane" $\endgroup$ Commented May 14, 2020 at 8:34

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