Flap retraction on landing

Land something like a 206, 185, 208B, A9, etc in a heavy cross wind, tell me the flaps dont make a diffrence.

Or just re-read what the others, as well as myself, have already stated on this thread.

I know you love that AFM Ron, but flying isn't always paint by numbers.
 
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the Six is another one of those that needs flaps up early to get weight on wheels and any kind of braking action.....without flat spotting a tire.

I had a friend who did that once.....:nono:
 
Ron Levy said:
I don't see how additional weight on the wheels will reduce the number of rocks thrown up, but I do see your point about getting the flaps out of the path of rocks thrown up by the main wheels. However, given the number of landing accidents involving loss of control after landing, and the paucity of cases of gravel damage to flaps, I don't see that as making it worth doing even on a gravel strip.
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For me it's about the control-ability. I feel like dumping the flaps reduces the tendency of the airplane to try to keep flying, especially in gusty wind. It makes the ground control a lot easier especially on surfaces such as grass, dirt or gravel.

Maybe it's just me, but I think it feels better.
 
In the POH for my PA-28-151, it specifically mentions retracting the flaps before applying the brakes.

Normally, the best technique for short and slow landings is to use full flap and enough power to maintain the desired airspeed and approach flight path. Reduce the airspeed during flareout and contact the ground at close to the stalling speed. After ground contact hold the nose wheel off as long as possible. As the airplane slows down, drop the nose and apply the brakes. There will be less chance of skidding the tires if the flaps are retracted before applying the brakes. Braking is most effective when back pressure is applied to the control wheel, putting most of the airplane weight on the main wheels. In high wind conditions, particularly in strong crosswinds, it may be desireable to approach the ground at higher than normal speeds with partial or no flaps.
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Ron Levy said:
And there are very, very few light planes where the takeoff roll is shorter than landing roll with flaps left extended, so there is almost never anything to be gained by retracting the flaps on landing unless you are planning to have the plane trucked out of the landing site.
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I used to agree with the above until I carefully read the Cessna PoH for the 172 and 152 when I started to actually plan landings at short grass fields with both airplanes.

The landing (and takeoff) distance tables come with a number of preconditions, such as "Maximum performance technique as specified in Section <whatever>." One of the performance techniques Cessna mentions in short field landings is retracting the flaps to maximize braking. It doesn't say how much to extend the landing distances in its table figures if flaps aren't immediately retracted, so one is advised to do so if there is a concern.

Example, using figures from the C-172M PoH:
Sea level takeoff
Calm winds
20 C
lightly loaded (1900 lbs)
On grass.
​
Takeoff:
580 ft ground roll, increase by 15% per notes (87 ft), yielding 667 ft.
1035 ft to clear 50 ft obstacle, with added ground roll, yielding 1122 ft.
​
Landing:
530 ft ground roll, increase by 45% per notes (239 ft), to 769 ft. Longer than the takeoff run of 667!
1265 ft to clear 50 ft obstacle, with added ground roll, yielding 1504 ft. Longer than the takeoff distance of 1122 to clear.
​
OK - I cheated a little bit in my scenario selection (but only because it was actually relevant to my flights!) A lightly loaded C-172 has moderately decent short field takeoff performance, so the takeoff distances become longer or comparable to the landing distances when landing on grass. Otherwise takeoff distances for heavily loaded machines on paved runways are the limiting factors, not the landing distances. Flaps up for braking in such cases may not be needed.

By the way, the same is true for the C-152: its ground rolls also stretch out by 45% on grass. In a number of cases that makes the takeoff distance shorter than the landing distance.
 
Ryanb said:
In 152/172's i retract during the rollout. It aids in braking by shifting the weight from toward the front to back on the mains and reduces skidding. (This is the way i was taught anyway)
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On those airplanes, the flaps generate max lift at 20 degrees, and most drag at 40°. With those electric flaps, you're actually increasing lift and reducing traction as the flaps slowly creep through the 20° point. Better to leave them alone. Manual flaps, as found in the 180/185 and Pipers, can be dumped rapidly for best braking.

Full up elevator places useful weight on the mains in a trike.

Dan
 
Ron Levy said:
I don't see how additional weight on the wheels will reduce the number of rocks thrown up...
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By shortening the time the airplane spends at speeds where rocks are thrown up. More traction equals better braking and a shorter ground roll.

Dan
 
that works for the first few hundred feet....but then drag rapidly decays as speed is reduced.
 
Dan Thomas said:
On those airplanes, the flaps generate max lift at 20 degrees, and most drag at 40°. With those electric flaps, you're actually increasing lift and reducing traction as the flaps slowly creep through the 20° point. Better to leave them alone. Manual flaps, as found in the 180/185 and Pipers, can be dumped rapidly for best braking.

Full up elevator places useful weight on the mains in a trike.

Dan
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I think this is worth mentioning as well. I rarely touched them when full in an electric flap 150/172. However, if they're at 10 or 20, pull'em
 
Challenged said:
My Beech Sierra has a placard to retract flaps upon landing to increase braking effectiveness.

Sent from my Nexus 7 using Tapatalk
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All of the Musketeers, Sports, Sundowners and Sierras I've flown have that placard. Get on the brakes with the flaps down on those birds is an easy way to flat spot and get flat tires.
 
I recently watched all four episodes of the series "Worst Place to be a Pilot" and time after time landing on the gnarliest airstrips of wet grass or muddy hillsides I never once saw any of them retract the flaps on rollout, at least not with the Porter or Caravan. That may be a Susi Air policy but I think it demonstrates that lifting the flaps on landing is of little or no benefit even in these extreme situations.
 
James331 said:
Land something like a 206, 185, 208B, A9, etc in a heavy cross wind, tell me the flaps dont make a diffrence.
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I've only flown the first two, and flaps certainly make a difference with them, but not one that would encourage me to go grabbing for them after landing before the aircraft was slowed and under control. I just don't feel I have anything to prove by showing how fast I can do things like that any more.
 
Seriously, how many of y'all are flying 152s and 172s off less than 1000'?:dunno:
 
You should see the pond I'm looking at landing in :yes:
 
Again, stipulating that dumping flaps right after touchdown may have its place...

And referring mainly to smaller, GA aircraft...

Despite all the alleged benefits, in a relatively long flying career flying a variety of planes into both paved and unpaved strips of varying lengths...

1) I have never made it a practice to retract flaps immediately on touchdown.

2) I have never flat-spotted a tire.

3) I have never run off the end of a runway.

4) i have only very, very rarely found myself "lifted" back into the air after initial touchdown - and in those cases it's been easily dealt with.

So, I still hold that, in spite of the alleged theoretical advantages, there's no real necessity to dumping flaps after touchdown as a normal procedure.

I see many, many pilots landing way, way faster than necessary. If a typical small plane is landed at or near it's stall speed - as we all had to demonstrate on the Private Pilot checkride - flap retraction right after landing will provide little or no benefit in the vast majority of cases.

For those who typically land 10, 15, 20kts or more fast, those are the pilots who may flat spot tires or be lifted back into the air or who find themselves out of runway. Getting rid of all the extra lift carried due to the excess speed may benefit them. But I'd still suggest losing most of their energy in the flare - not on the runway.

But all that said, if it's a technique that pleases you, by all means keep it up. Like many things in flying, it ends up being a matter of personal preference.
 
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FastEddieB said:
Again, stipulating that dumping flaps right after touchdown may have its place...

And referring mainly to smaller, GA aircraft...

Despite all the alleged benefits, in a relatively long flying career flying a variety of planes into both paved and unpaved strips of varying lengths...

1) I have never made it a practice to retract flaps immediately on touchdown.

2) I have never flat-spotted a tire.

3) I have never run off the end of a runway.

4) i have only very, very rarely found myself "lifted" back into the air after initial touchdown - and in those cases it's been easily dealt with.

So, I still hold that, in spite of the alleged theoretical advantages, there's no real necessity to dumping flaps after touchdown as a normal procedure.

I see many, many pilots landing way, way faster than necessary. If a typical small plane is landed at or near it's stall speed - as we all had to demonstrate on the Private Pilot checkride - flap retraction right after landing will provide little or no benefit in the vast majority of cases.

For those who typically land 10, 15, 20kts or more fast, those are the pilots who may flat spot tires or be lifted back into the air or who find themselves out of runway. Getting rid of all the extra lift carried due to the excess speed may benefit them. But I'd still suggest losing most of their energy in the flare - not on the runway.

But all that said, if it's a technique that pleases you, by all means keep it up. Like many things in flying, it ends up being a matter of personal preference.
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I'm with you, I don't get it, I don't really get it as that big of a deal. When I land, the plane has stalled, it's not inclined to fly, when I let the nose down, it's further disinclined to fly. If we are talking an advantage in runway use by dumping the flaps, we are talking about people who land way too fast, that I see as common. I don't flat spot tires either as I hardly get on brakes at speed. Never once have I been in a situation that necessitated dumping the flaps on touchdown.
 
I do it in the 172, just as soon as the aircraft is down on all 3 and stable the flap switch comes up immediately. My home strip is only 2500' with power lines on both ends, so I've effectively only got about 2000' to play with, making every landing a short-field landing. Airspeed control is key but I still don't want a gust of wind trying to convince the airplane to get light. I don't dump the flaps to enable heavier braking - I dump the flaps to get a little more grip on the tires to make the transition from an airplane to a land vehicle a little quicker.
 
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I TRY to remember to retract them as I am turning off the runway. I actually am embarrassed if I forget and someone sees me on the Ramp with flaps still deployed.
 
airguy said:
I do it in the 172, just as soon as the aircraft is down on all 3 and stable the flap switch comes up immediately. My home strip is only 2500' with power lines on both ends, so I've effectively only got about 2000' to play with, making every landing a short-field landing. Airspeed control is key but I still don't want a gust of wind trying to convince the airplane to get light. I don't dump the flaps to enable heavier braking - I dump the flaps to get a little more grip on the tires to make the transition from an airplane to a land vehicle a little quicker.
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That's a good situation to keep your flying that much sharper. Most of my work is out of a 4,000 feet runway with the single turn off about 1,500 feet from the South End. When using the 35 I try to set down on the end of the runway and see how far short of the turnoff I can get it down to taxi speed.

Having a goal like this on many landings helps to keep you from getting lazy and throwing out the need for precision. Your situation has more motivation for precision than mine though.:)
 
airguy said:
I do it in the 172, just as soon as the aircraft is down on all 3 and stable the flap switch comes up immediately. My home strip is only 2500' with power lines on both ends, so I've effectively only got about 2000' to play with, making every landing a short-field landing. Airspeed control is key but I still don't want a gust of wind trying to convince the airplane to get light. I don't dump the flaps to enable heavier braking - I dump the flaps to get a little more grip on the tires to make the transition from an airplane to a land vehicle a little quicker.
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That's a good situation to keep your flying that much sharper. Most of my work is out of a 4,000 feet runway with the single turn off about 1,500 feet from the South End. When using the 35 I try to set down on the end of the runway and see how far short of the turnoff I can get it down to taxi speed.

Having a goal like this on many landings helps to keep you from getting lazy and throwing out the need for precision. Your situation has more motivation for precision than mine though.:) My situation only sets me up for a possible loss of face. Yours sets up for more possible loss than that.
 
airguy said:
I don't dump the flaps to enable heavier braking - I dump the flaps to get a little more grip on the tires to make the transition from an airplane to a land vehicle a little quicker.
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Not clear on that concept. If not for braking, would not leaving flaps down add drag that would aid the short field attempt?

And if you land in a full stall, would not the transition to "land vehicle" be nearly instantaneous?

Like I said, I've done lots of short field landings, and not one of the required dumping flaps.
 
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MBDiagMan said:
Having a goal like this on many landings helps to keep you from getting lazy and throwing out the need for precision. Your situation has more motivation for precision than mine though.:)
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When my Cirrus was based at HWO, my goal was to exit mid-field - about 1,500'.

Never needed to dump flaps to accomplish that.
 
Ron Levy said:
And there are very, very few light planes where the takeoff roll is shorter than landing roll with flaps left extended,
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There are lots of places where the runway available for landing (e.g., displaced thresholds, obstacles on short final, etc.) is considerably less than the runway available for takeoff.
 
airguy said:
I do it in the 172, just as soon as the aircraft is down on all 3 and stable the flap switch comes up immediately. My home strip is only 2500' with power lines on both ends, so I've effectively only got about 2000' to play with, making every landing a short-field landing. Airspeed control is key but I still don't want a gust of wind trying to convince the airplane to get light. I don't dump the flaps to enable heavier braking - I dump the flaps to get a little more grip on the tires to make the transition from an airplane to a land vehicle a little quicker.
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2000 feet is not a short field in a 172. Not even close, really.

1500 feet in no wind becomes marginal.

1000 feet is short.

Ground roll is 530 feet at sea level on a standard day with no wind. It can be arbitrarily shorter in the presence of wind.

My home airport is 2400 feet. People land King Airs there, and other aircraft considerably larger than a 172. I get really ****ed off if I need as much as 1000 feet past the threshold to stop ('cause it means a long taxi and I'd really better be able to handle the airplane better than that).

And I don't mess with flaps on touchdown. I've found it makes no difference if I don't try to land much too fast. When the plane is done flying, the wheels come down and stay there.
 
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One must understand what flaps produce, one must also understand that you DONT land in a stall :rolleyes2:


As to Ron's question about my flaps, that wing make a good deal of lift, especially with the drooping ailerons, this is a good thing until I turn into a car or a boat, then I don't want any of that lift anymore, luckily there is a handle destroys quite a bit of that lift. Think of it as a poor mans spoilers.
 
FastEddieB said:
Not clear on that concept. If not for braking, would not leaving flaps down add drag that would aid the short field attempt?

And if you land in a full stall, would not the transition to "land vehicle" be nearly instantaneous?

Like I said, I've done lots of short field landings, and not one of the required dumping flaps.
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Well that begs the question: is there a theoretical floor of lift? Does a wing generate lift at VS0 minus 1kt? And therefore it would be prudent that you're adding margin above VS1
 
Jaybird180 said:
Well that begs the question: is there a theoretical floor of lift?...
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Not really, any flow over the airfoil is going to create some lift as is evidenced by the wings of a parked airplane rocking in the wind. The amount of lift is also influenced by the AOA up to the critical point where a stall occurs. When the flaps are deployed you have a different airfoil, one that creates greater lift at a slower speed but it's all relevant because you land at that slower speed.

In the OP's original post he specifically asked about Cessna 152/172's which are both tricycle geared aircraft with pretty much identical wing and flap designs driven by an electric motor. By the time you have flared to the stall point, planted the mains and dropped the nose wheel you have put the airfoil into an AOA that will not support enough lift for further flight. You are also in a constant deceleration and the flaps at that point, as designed, are providing aerodynamic drag to help slow the airplane down.

In that specific scenario I see no advantage to raising the flaps early.
 
James331 said:
One must understand what flaps produce, one must also understand that you DONT land in a stall :rolleyes2:
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I think that's just semantics.

I was taught to keep the plane flying until it literally can't be kept in the air.

IOW, conditions permitting, the perfect landing is one where the stick hits the aft stop just as the mains touch. And we used to call that a "full stall" landing, whether that was a slight misnomer or not.

It was, in fact, the same stick position that DID result in a full stall at altitude, so even allowing for ground effect, I think it's a close approximation to a full stall.

And though we can bicker about how "full" a "full stall" landing is, and whether some lift is still being produced, the chart below shows how quickly lift falls off beyond the critical angle of attack:

fig9.jpg
 
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FastEddieB said:
I think that's just semantics.

I was taught to keep the plane flying until it literally can't be kept in the air.

IOW, conditions permitting, the perfect landing is one where the stick hits the aft stop just as the mains touch. And we used to call that a "full stall" landing, whether that was a slight misnomer or not.

It was, in fact, the same stick position that DID result in a full stall at altitude, so even allowing for ground effect, I think it's a close approximation to a full stall.

And though we can bicker about how "full" a "full stall" landing is, and whether some lift is still being produced, the chart below shows how quickly lift falls off beyond the critical angle of attack:

fig9.jpg
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In my book a full stall is when the nose drops. Flare to the shaker in a larger plane, that's well, bad form.

Still taking the flaps out is similar to deploying ground spoilers.
 
James331 said:
In my book a full stall is when the nose drops.
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I agree - at altitude.

In ground effect, the elevator can keep the nose up even as the wing stalls.

It may not be a full stall, but you are definitely in the area where any further increase in angle-of-attack causes a decrease in lift. As the stick nears it's aft limit one can feel the lift dissipating as the mains drop on.

As far as big planes and stick shakers, that's beyond my level of expertise. I realize that jets are typically not held off to a stall - for reasons that do not apply to most small, GA planes.
 
RotorAndWing said:
You keep saying that, but it's not true. :nonod:

Have you flown anything with ground spoilers?
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Please explain to me the purpose of a spoiler.

Please explain what happens to lift when you take the flaps back to 0.
 
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