Spoilers/Flaps on landing Options

[boeing_joe]

Hey all,

I've seen heaps of vids on this site - and only just noticed that some pilots retract the flaps immediatley after touchdown while others wait until they have taxied of the runway. Why is this? Is it personal preference or something to do with fuel/payload, wx or the runway lenth etc

Any help is appreciated!

Joe

[Empress]

Raising the flaps after landing helps to further kill lift generated by the wings and adds weight to the wheels which increases the effectiveness of the brakes.

[Hawker]

What kinda airplanes?

[airlinepilote]

Never seen a video like that boeingjoe.
Can you sent some links?
That will help

[aircadet]

It would be weird to retarct the flaps right after landing. I have only heard of landing with reduced flaps due to crosswinds. Weird. Maybe the pilot was about to stall and had to retract flaps??

adds weight to the wheels which increases the effectiveness of the brakes

Sorry to ask, but howwill retracting the flaps cause the increase in weight?

[yaarpanjabi]

Sorry to ask, but howwill retracting the flaps cause the increase in weight?

Since flaps increase the lift produced by a wing, retracting them gets rid of any lift that they are producing, thereby the lift reduced from the flaps is transferred to the wheels. Hope that makes sense.

Referring to the original post, it probably wouldn't make a huge difference on the big jets since they use spoilers. As part of my PPL training, my instructor told me specifically to retract the flaps BEFORE I start braking as it will decrease the changes of a wheel lock-up which would cause a skid. As said earlier, it also increases the braking effectiveness.

[Hawker]

Maybe the pilot was about to stall and had to retract flaps??

If the pilot retracted the flaps if he was going to stall... this would be very bad. This would surely MAKE him stall!

[Becky_KSTS]

In the case of General Aviation (GA) when practicing short field landings in the C-172, I was always taught "flaps up, yoke back, breaks on". Like Empress and Yaarpan said, it takes the lift out of the wings and gets those tires firmly planted on the runway. If you are not making a short field approach (in the case of GA), it has been argued that it is a safer practice to "clean up the plane" after leaving the runway and are holding at the taxiway. I have done both and if I have time, would rather do the latter.

[B22EL]

Weird. Maybe the pilot was about to stall and had to retract flaps??

LOL, you really need to read up.

Flaps change the shape of the wing so that it produces more lift. They are used on takeoff to reduce the V1 Vr and V2 speeds, allowing for a shorter takeoff roll, and they are used on final approach for slower approach speeds and shorter landing rolls.

So if the aircraft was about to go into a stall, retracting the flaps would make the situation 10x worse.

[AirRabbit]

Hey Guys – all of this talk about raising flaps to decrease lift and extending flaps to increase lift HAS to be conducted with the understanding that the lift generated (regardless of the flap setting) is due to the airflow over/under the wing. What causes the air to flow over/under the wing? Thrust; pushing the airplane and the wing through the air. Yes, it is true that by extending flaps all the way (for landing) the airplane can fly at a slower speed – but, as I’m sure you all recall, there is a significant increase in thrust required to be able to fly at this slower airspeed. Why? Two primary reasons and they’re both “drag.” The first is the induced drag generated with the increased lift. The second is the form drag from the flaps being further deflected into the otherwise clear air. Those of you who fly will recognize the feeling you get if you trim the airplane for straight and level flight with an approach flap setting and select full flaps, changing nothing else. The airplane slows down almost immediately (directly related to the inertia of the airplane of course) and you either need to add a bunch of power or you need to push the nose over to descend and add some power as well.

The next time you have the opportunity, watch the flaps as they extend and retract. If you’re watching a commercial airplane, the first few increments of flap extension generally only increases the lifting area of the wing. In other words the flaps move rearward, with very little downward deflection. In the intermediate ranges, there is some additional rearward movement but a substantial increase in the downward deflection. And the last increments are almost entirely downward deflection. So, knowing what effect flaps have on the lifting capability of the wing, and keeping the relative movement of the flaps in mind, what happens as the flaps are retracted from fully extended to fully retracted? Yes, lift will be reduced – but that lift is directly related to the amount of “oomph” being used to push that configuration through the air. The other things that get smaller are those drag components; less lift – less induced drag; less deflection into clear air – less form drag.

The other thing you need to be aware of in these discussions is the airspeed that you’re going to be dealing with. Remember that Vref (the speed you should be holding down final – assuming a no-wind condition) is 30% above the stalling speed for that configuration. And the takeoff safety speed (commonly referred to as V2) is about 20% above the stalling speed for that configuration. Sometime, just for grins, you might want to check your airplane manual for these speeds for the same gross weight.