bragi
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When To Retract Flaps During Landing Run?

Mon Sep 13, 2004 9:06 am

The topic pretty much sums up the question, I was wondering at what time during the landing run is best to retract the flaps?
I was wondering if it's done soon after touchdown to improve braking action, or is it done later to use the drag the flaps provide to slow down the aircraft?
-It may seem as insignificant question, I just want to know for sure. Smile

edit: Spelling error

[Edited 2004-09-13 02:07:27]
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G4Doc2004
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RE: When To Retract Flaps During Landing Run?

Mon Sep 13, 2004 9:35 am

SOP from every instructor I flew with including my multi-engine, as well as SOP for the corporate flight dept I work for is to retract the flaps after departing the active runway. This item is on the "After Landing" checklist which is performed during taxi.
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liamksa
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RE: When To Retract Flaps During Landing Run?

Mon Sep 13, 2004 10:00 am

G'day Bragi

I was wondering if it's done soon after touchdown to improve braking action, or is it done later to use the drag the flaps provide to slow down the aircraft?

On the big jets you get the best of both worlds. On touchdown you may have noticed the ground spoilers on top of the wing deploying on touchdown. These effectively destroy the lift, getting the 'weight-on-wheels' and allowing plenty of friction between the tyre and runway. As well as this you get the drag from the enormous flaps on some types so there's no problem retracting them once you've exited the runway.
 
learpilot
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RE: When To Retract Flaps During Landing Run?

Mon Sep 13, 2004 12:38 pm

A guy I used to work with tried to retract the flaps right after touchdown to "improve braking action", but grabbed the landing gear handle. Result: totalled Beech Baron.

Best to wait until you are off the runway at a slow speed (or better yet, stopped) so you have time to make sure you have the right knob in your hands. (stop snickering)  Big grin
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rendezvous
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RE: When To Retract Flaps During Landing Run?

Mon Sep 13, 2004 5:49 pm

The Cessna 172S manual says for a short field landing to retract the flaps immediately after touchdown, so you can get better braking action. I'm not sure how much distance it would actually make to the landing run though.

In situations where it's not imperative, it's best not to create unecessary things to do during a critical phase of flight.
 
SlamClick
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RE: When To Retract Flaps During Landing Run?

Mon Sep 13, 2004 11:41 pm

This discussion really needs to be type-specific.

I would not presume to argue with the manufacturer's handbook. One thing to consider though. The important difference between takeoff flaps and landing flaps is that the takeoff setting produces more lift and less drag. If you land with a landing flap setting and begin to retract the flaps, you must pass through the takeoff range on the way up. You might be producing more lift, not less, for a time.

Another general piece of advice. Retracting the flaps is not as important as maintaining 1.) control of the airplane and 2.) situational awareness.

I'd say leave them down until you clear the runway.

When I'm performing PNF duties, I have a little flow I perform as we exit the runway. Just off the top of my head it is sort of like this:
  • Retract the ground spoilers

  • Retract the flaps

  • Turn off the transponder

  • Call ground control

  • reset the flight guidance controls on the glareshield

  • Stop the elapsed-time clock

  • Reach for the after-landing checklist

  • Maybe start the APU


  • None of these things happen while we are still rolling out.


    [Edited 2004-09-13 16:46:29]
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    bragi
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    RE: When To Retract Flaps During Landing Run?

    Tue Sep 14, 2004 10:32 am

    I myself am used to retract the flaps when vacating the runway (my instructor told me in initial training; "Don't stop flying even though your wheels have touched the ground.") I always try to adhere to that rule! Big grin

    I was just curios to hear your comments on the subject....

    Maybe the immediate flap retraction would be a bigger factor if it wasn't for the spoilers?
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    cancidas
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    RE: When To Retract Flaps During Landing Run?

    Tue Sep 14, 2004 11:24 pm

    i've done so a few times flying a C172RG into relatively short fields. then again, if the aircraft has spoilers there is no reason to do so. it does help to improve braking action because the wing is no longer producing as much lift as it was with the flaps down. then again, this is minimal and really not too useful in every day flying, especially when you have a longer strip.
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    BMAbound
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    RE: When To Retract Flaps During Landing Run?

    Wed Sep 15, 2004 12:23 am

    I was taught not to touch the flaps on the runway, mainly because the day I move on to complex aircraft, I may retract the gear instead of the flaps. That would kinda ruin the day, wouldn't it?

    johan
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    SlamClick
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    RE: When To Retract Flaps During Landing Run?

    Wed Sep 15, 2004 2:48 am

    If you must retract the flaps on the landing roll in order to get the plane stopped on the available runway, it might be argued that you used bad judgement landing the aircraft in question on this particular runway. I mean how close are you willing to fly to an absolute limit?

    If you do not have to retract them to get the plane stopped - don't do it. Pay attention to flying the plane. It is a little like talking on a cell phone while driving a car in heavy traffic - how damn important could a phone call be?

    Maybe we should light a cigarette while firing a shotgun too?

    Sorry about the sarcasm but I'm no fan of doing things just because someone thinks they look cool. Ever seen a guy hit both starters at the same time on a light twin? Me too. I've also seen a guy do it after clearing one prop.
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    N766UA
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    RE: When To Retract Flaps During Landing Run?

    Wed Sep 15, 2004 4:41 am

    I often retract the flaps and push in the carb heat right after I touch down. This completes cleaning up for landing and it helps alot with braking. Retracting flaps also helps reduce the floating action that Cessnas are prone to.

    [Edited 2004-09-14 21:41:58]
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    rendezvous
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    RE: When To Retract Flaps During Landing Run?

    Wed Sep 15, 2004 2:42 pm

    The only time I've actually retracted them on landing was during a flight test after a simulated engine failure. I landed on the field (airport) and retracted them, then proceeded with heavy braking.

    Other than that, I think it causes too much distraction to reach for the flap lever while the plane is still half flying.
     
    SkyGuy11
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    RE: When To Retract Flaps During Landing Run?

    Wed Sep 15, 2004 3:46 pm

    I dunno, if you can feel and see that you have the FLAP handle in your hand, and know the airplane well enough to realize it's the correct switch, I don't see why not. You can walk and chew gum, can't you? Of course I can also see the benefit to waiting until you're stopped. I say do whatever works for you.

    Hell in a touch and go you're not only retracting flaps, but you're changing from landing config to takeoff config. If you won't touch the flap handle on the runway how will you ever do a T+G?
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    Mr.BA
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    RE: When To Retract Flaps During Landing Run?

    Wed Sep 15, 2004 5:25 pm

    I sort of agree with SlamClick. Retracting the flaps immediately touch down is deemed unnecessary and if you have to just to make sure you stop in time I think you're taking a risk too much. The benefits are stopping within a shorter distance but I don't think you would need that little amount of difference unless you're pushing it to the limits. I mean it's not wrong in the sense to retract the flaps after touchdown to achieve better braking and it may seem very routine after sometime but I still think the pilot should be fully concentrated on flying the plane especially at this critical stage of flight and distraction is surely a no when landing in bad weather.

    It's just not the same as chewing gum as you walk. It's more like you retracting flaps to the next level just after take off to improve your climb rate.
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