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Landing Question

Landing Question

Old Jan 2, 09, 3:28 pm
  #1  
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Landing Question

I always wondered why doesn't the pilot retract the flaps immediately after landing on the runway. They seem to wait until they are on the taxi way? I thought once the plane has fully landed they can retract the flaps.
danielonn is offline  
Old Jan 2, 09, 4:20 pm
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for flying smaller cessna type planes, flap retraction is on a checklist completed after the plane has cleared the active runway. This is simply to expedite clearing of the runway and reduce the chance you will get distracted and somehow mess up. Its probably similar reasoning for larger commercial aircraft.
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Old Jan 2, 09, 4:40 pm
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Flaps

It is safety discipline. The idea is to focus on the landing, the stopping, and exiting the runway promptly to make it available for the next plane. There is plenty of time to take care of after landing checklist items after clearing the runway.
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Old Jan 2, 09, 7:13 pm
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I also suspect that flaps down during runway roll after landing increases drag and supplements using spoilers to slow down the plane prior to moving on to a taxiway.
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Old Jan 3, 09, 8:44 am
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Originally Posted by tonywestsider View Post
I also suspect that flaps down during runway roll after landing increases drag and supplements using spoilers to slow down the plane prior to moving on to a taxiway.
This is also true, but as previous posters have mentioned, the primary reason is safety. There's simply too much happening in the cockpit during that phase of flight to worry about getting the flaps up. It's important to note that on many commercial jets, the flap handle is located right next to the landing gear handle. There have been instances where in the hustle of it all, the wrong handle was pulled. (Most modern airliners now have a safety mechanism that prevents gear retraction with the full weight of the aircraft resting on them.)
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Old Jan 3, 09, 4:20 pm
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Originally Posted by tonywestsider View Post
I also suspect that flaps down during runway roll after landing increases drag and supplements using spoilers to slow down the plane prior to moving on to a taxiway.
Yes, flaps result in more drag, but they also generate more lift. The increased lift makes wheel braking less effective (less weight on the tires). A technique for short-field landing is to raise the flaps (on the ground) to improve braking. This applies to small aircraft, I'm pretty sure not to large ones though.

Still, retracting flaps on the landing roll-out is normally discouraged. The landing and roll-out is a critical maneuver and demands all of the pilot's attention. You just don't want to be messing with other things during that phase.
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Old Jan 4, 09, 1:13 am
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What's the hurry? There are more important priorities immediately after touchdown than raising the flaps.

The ground spoilers kill the lift on touchdown so raising the flaps shouldn't make much difference with regard to the amount of weight on the wheels during braking. Some airplanes, i.e. J31/J32, use the flaps for lift-dump instead of ground spoilers. The flaps are extended well past the normal landing setting to kill the lift and increase drag.

Not sure why it was said that the flaps and gear handles are located close together on airliners. They are not. The flap handle is usually down on the right side of the center console while the gear handle is up on the instrument panel.
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Old Jan 4, 09, 1:30 am
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Originally Posted by tonywestsider View Post
I also suspect that flaps down during runway roll after landing increases drag and supplements using spoilers to slow down the plane prior to moving on to a taxiway.
Although spoilers do contribute to drag on the aircraft, the majority of the work they do is in separating the air from the top of the wing, drastically reducing lift.
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Old Jan 4, 09, 8:49 am
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Originally Posted by johnnybgood3 View Post
Although spoilers do contribute to drag on the aircraft, the majority of the work they do is in separating the air from the top of the wing, drastically reducing lift.
Hence the name "spoilers." Speed brakes, do the opposite: add lots of drag, little effect on lift.
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Old Jan 4, 09, 1:17 pm
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Originally Posted by After Burner View Post
Hence the name "spoilers." Speed brakes, do the opposite: add lots of drag, little effect on lift.
Yet the speed brakes and spoilers are often the exact same panels doing the exact same thing.
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Old Jan 4, 09, 8:36 pm
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PropWasher is offline  
Old Jan 4, 09, 11:44 pm
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Another related question (re: landing)

Why is that some airlines (LH and SQ, for instance) consistently have the most graceful of landings, IMO? These planes touch down ever so gently, while this isn't always the case in some of the other airlines.

Just curious!
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Old Jan 5, 09, 10:45 am
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Originally Posted by malgudi View Post
Another related question (re: landing)

Why is that some airlines (LH and SQ, for instance) consistently have the most graceful of landings, IMO? These planes touch down ever so gently, while this isn't always the case in some of the other airlines.

Just curious!
Are you comparing apples with apples here? Same aircraft type, same airport, same runway, same winds, etc.?

As a pilot of a small airplane, I usually strive for gentle, passenger-pleasing landings. That's no problem on a 10,000 ft runway. But on a short runway you don't have the luxury of gradually losing speed, holding the tires a few inches above the surface and waiting for the airplane to gently settle down. That uses up a lot of runway. Sometimes you need to "slam it down" firmly and get the brakes on. Even on a long runway, it's often desirable to slow down in time to exit on one of the first taxiways.

Someone who pilots heavy metal might chime in here with their perspective, but I imagine the principles are the same.
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Old Jan 5, 09, 11:56 am
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I have a commercial pilot friend who once commented to me the difference between "good" landings as far as pilots and pax are concerned.

Passengers consider a 'good' landing to be a gentle one.

Pilots consider a 'good' landing to be one where the wheels touch down early enough that you still have thousands of feet of runway out in front of you.

In other words, a 'gentle' landing in the middle of the runway is a bad landing; a somewhat bumpy one right at the start of the runway is a good one.
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Old Jan 5, 09, 12:22 pm
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Flaps are used for take offs too (was it 25% or 50% for the 747?), so if the plane needs to take off again after touching down (in emergency situations), the flaps are still there, better to have more instead of less?
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