Author Topic: Flare During Landing  (Read 438 times)

Offline Palace Cobra

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Re: Flare During Landing
« Reply #15 on: May 23, 2020, 12:09:24 PM »
The primary factor in ground effect is a reduction in drag. Wingtip vortices are disrupted resulting in an almost 50% reduction in induced drag. The wing is not simply producing more lift as maximum lift is generated outside of ground effect. The wing is primarily experiencing an increased efficiency as the lift/drag ratio is improved.   This is not because the L gets bigger in as much as the D gets smaller. 

Reduced drag also allows the airplane to "fly" with far less thrust. It will also stall at a lower angle of attack.

It's extremely complicated but in essence it is a function of drag reduction not lift increase.

Offline FLS

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Re: Flare During Landing
« Reply #16 on: May 23, 2020, 03:52:31 PM »
Vraciu made that exact point in his PM.

However the coefficient of lift is also increased in ground effect so for a given AOA there is more lift in ground effect along with the drag reduction.

I assume this is because the circulation of air pushing the ground is more effective than air pushing air.

Offline Palace Cobra

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Re: Flare During Landing
« Reply #17 on: May 23, 2020, 04:20:35 PM »
The change in lift coefficient is marginal. The overriding factor is drag reduction.

Offline FLS

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Re: Flare During Landing
« Reply #18 on: May 23, 2020, 05:15:51 PM »
Every published reference mentions the lift increase but none of them describe it as marginal. They all seem to think it's the more noticeable effect.

It's what causes the " floating on a cushion of air " that makes the flare challenging.

Offline Palace Cobra

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Re: Flare During Landing
« Reply #19 on: May 23, 2020, 05:39:24 PM »
Any chart that shows the effect on lift shows it as marginal.

It's certainly not as big as the change in induced drag which is massive. 

Wings create "more" lift only three ways:

1) Increase in airflow (speed).
2) Increase in angle of attack.
3) Increase in wing area.

Flaring is not the least bit challenging. It's slow flight at idle close to the ground.

The whole "cushion of air" sloppy language is where the problem lies. Vortices and their relationship to drag is the key to everything. That's why aspect ratios and winglets matter so much.

Offline FLS

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Re: Flare During Landing
« Reply #20 on: May 23, 2020, 07:03:23 PM »
Your point seems to be that increasing the coefficient of lift does not increase lift. Isn't that what slats and flaps do?

Offline Puma44

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Re: Flare During Landing
« Reply #21 on: May 23, 2020, 07:14:32 PM »
Then, there’s the drag associated with landing gear up.......



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Offline Wildin

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Re: Flare During Landing
« Reply #22 on: May 24, 2020, 12:37:30 PM »
Had to land gear up in a Cessna 210 at Lafayette LA after a pin in the gear failed. Weird feeling when you sink lower than usual on landing. Very fond of ground effect as it saved my bacon one night in Bard CA when throttle linkage failed while spraying a cotton field. Quick check of mags, fuel valve, dump load, trying to remember what obstacles on other end of field
beyond reach of lights, I think I was actually pulling up on harness lol, so relieved to see  a field of alfalfa across a road and ditch that the lovely ground effect helped me clear. Knees actually shook a little when I deplaned.

Offline Busher

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Re: Flare During Landing
« Reply #23 on: May 24, 2020, 04:56:09 PM »
Had to land gear up in a Cessna 210 at Lafayette LA after a pin in the gear failed. Weird feeling when you sink lower than usual on landing. Very fond of ground effect as it saved my bacon one night in Bard CA when throttle linkage failed while spraying a cotton field. Quick check of mags, fuel valve, dump load, trying to remember what obstacles on other end of field
beyond reach of lights, I think I was actually pulling up on harness lol, so relieved to see  a field of alfalfa across a road and ditch that the lovely ground effect helped me clear. Knees actually shook a little when I deplaned.

You still make a living crop dusting?
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Offline Wildin

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Re: Flare During Landing
« Reply #24 on: May 25, 2020, 04:33:09 AM »
No, in 1970 or 71 we lost 2 pilots, 25% of us flying in the Yuma AZ area and my daughter was born all of which led to me deciding to quit my adrenaline addiction and seek other work.

Offline mikeWe9a

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Re: Flare During Landing
« Reply #25 on: June 09, 2020, 02:15:49 PM »
Vraciu made that exact point in his PM.

However the coefficient of lift is also increased in ground effect so for a given AOA there is more lift in ground effect along with the drag reduction.

I assume this is because the circulation of air pushing the ground is more effective than air pushing air.

The increased lift is primarily due to the disruption of wingtip vortices - the vortices, in addition to creating drag, allow high static pressure air to flow over the wingtip and onto the upper surface of the wing.  This reduces the low pressure effect on the upper surface, reducing lift.

Mike

Offline save

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Re: Flare During Landing
« Reply #26 on: June 11, 2020, 01:29:09 PM »
I flew mostly taildraggers IRL, since we normally have 0 crosswind in AH, IRL landings are much harder, we said - as the main gear has touching the ground, you had half the work left - to keeping it from groundlooping. often landing on one main gear with the wing down into the wind
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Offline Busher

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Re: Flare During Landing
« Reply #27 on: June 11, 2020, 05:53:14 PM »
I flew mostly taildraggers IRL, since we normally have 0 crosswind in AH, IRL landings are much harder, we said - as the main gear has touching the ground, you had half the work left - to keeping it from groundlooping. often landing on one main gear with the wing down into the wind

I agree. All my initial time was in Tdrggrs - Aeronca's, Cubs, Luscombes, etc.
If HT ever made landings like real life, crosswinds or not, very few would get a landed successfully without a lot of practice.
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Offline hitech

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Re: Flare During Landing
« Reply #28 on: June 23, 2020, 09:48:43 AM »
Depend which piece of the landing you are speaking about.

The touch down is slightly easier  in AH. But all the other parts of the landing like down wind, the judging when to turn base, and base to final. Speed and targeting touch down point are all way easier in real life.

As far as the rudder control on ground , the issue is that almost all your response in a tail dragger keeping it straight is do to feel of side load in the seat of your but.  Hence one of those things there is no way to model it 100 % like the real aircraft and produce an accurate result.

HiTech