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Would this not be smart to do because you may come in a little fast, therefore the flaps would send you back up? Or would you absolutely want flaps in this situation

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    $\begingroup$ Read up on the story of the Gimli Glider - how to fly and land a large modern passenger jet without any engines. $\endgroup$ – Flydog57 Feb 10 '20 at 22:40
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    $\begingroup$ Flaps are controlled by hydraulic systems which are powered by the engines. No engines, no flaps. Aircraft are usually equipped with ram air turbines for this case, but they often do not provide enough power for flaps. $\endgroup$ – jcaron Feb 10 '20 at 23:10
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Flaps steepen the descent angle - in other words, you run the risk of falling short of the runway. So in a glide you keep the flaps up until you can be certain of making the landing point. Once the landing is guaranteed, you can then deploy gear as well as flap to slow down as much as possible - being aware that these actions will further reduce the gliding range, so constant reevaluation is required.

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That would be up to the discretion of the flight crew, what forced landing site they selected, approach route, etc. Typically deployment of flaps in a forced landing scenario will only be done once the airplane is guaranteed to make the landing site by gliding in that landing configuration.

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You would certainly prefer to have flaps available in order to reduce landing speed. If so, the pilot in command has discretion whether using flaps is appropriate to the situation. Unfortunately, the loss of all engines may prevent flaps from being deployable. In two of the most famous airline no-engine landings I can think of, the Gimli Glider and Air Transat Flight 236, flaps could not be used due to lack of hydraulics.

In the case of US Airways Flight 1549, however, the APU was used to provide hydraulic pressure (which was impossible in the other flights mentioned, since there was no fuel left in those cases). Partial flaps were used in the ditching.

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Yes flaps would be used when landing the 737 with the loss of double engine failure. A double engine failure landing is an Emergency Procedure. Intentionally landing flaps-up with a double engine failure creates an unnessary Second Emergency.

A double engine failure flaps-up stopping distance may exceed runway length & the speed limits of the tires.

The Airbus flap system is electrical only.

The Boeing 737 flap system is normally hydraulically operated. In the event of a Double-Engine failure, the 737 flaps can be extended electrically.

A 737 double engine failure landing is similar to a screwed-up parachute landing...there are no do-overs.

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    $\begingroup$ "The Airbus flap system is electrical only." -> No, it isn't: "The motors use green and blue hydraulic power for slats and yellow and green power for the flaps." (A320 FCOM - Flight Controls) $\endgroup$ – Bianfable Oct 16 '20 at 21:49
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    $\begingroup$ While a dual-engine failure is certainly quite the emergency, I'm not so sure about it being an Emergency Procedure. Do you have a checklist that gives steps -- i.e. a procedure -- for such a landing in a 737? I've done it in the sim, although not as a procedure -- you're well beyond all of our checklists if you're landing both-engines-out. (The checklist we have for Dual Engine Failure consists of steps to get one or both restarted.) I don't think this answer adds anything to the other answers here. $\endgroup$ – Ralph J Oct 17 '20 at 4:24

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