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Old Oct 25, 2012, 12:08 PM
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United States, TN
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How To Eliminate Landing Bounce?

I am frequently getting a significant bounce on my landings. This is happpening with my Apprentice trainer (tricycle gear) and several float planes that I have. What might be the main cause(s) of this happening?

Thank you.
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Old Oct 25, 2012, 12:11 PM
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Lnagel's Avatar
Moab, Utah, USA
Joined Apr 2003
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Landing too fast.

Larry
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Old Oct 25, 2012, 12:42 PM
K_B
1D Flyer
United States, AK, Anchorage
Joined Sep 2012
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It could be a number of things. Sounds like you're not keep the nose down (about 10 degrees down) and once the plane gets in ground effect, you lose your lift and the plane falls out of the sky. This is usually my problem if I end up clunking it in.

When flying on floats, you want to keep a little bit of throttle on until you actually hit the water.

This might be helpful:

Flite Test - Horizon Hobby Flying On Water - FLITE TIP (7 min 59 sec)
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Old Oct 25, 2012, 12:55 PM
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dedStik's Avatar
United States, VA, Virginia Beach
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Coming in too hot and or wrong angle of attack or not flaring prior to touch down.
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Old Oct 25, 2012, 02:39 PM
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South Wales U.K.
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Also check the angle the wing sits at on the ground. With trike undercarriage it helps to have some negative wing angle to destroy any lift when on the ground.

Springy undercarriage also can bounce a model about quite a lot.
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Old Oct 25, 2012, 09:37 PM
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Moab, Utah, USA
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Originally Posted by K_B View Post
It could be a number of things. Sounds like you're not keep the nose down (about 10 degrees down) and once the plane gets in ground effect, you lose your lift and the plane falls out of the sky.
You have everything backwards. The farther down the nose is, the faster the plane will fly and the higher it will bounce. Ground effect increases lift.

Larry
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Old Oct 25, 2012, 10:42 PM
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Canada, BC, Port Coquitlam
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In my experience, floaty high wingers with low wing loading numbers, are the most difficult to land smoothly (without bouncing). It could be the undercarriages are springier but more likely because of ground effect, or fact that their low weight just allows them to keep flying with a less than a perfectly flared, smooth touch down.

On the other hand, it is easier for me to firmly plant or grease in, a low winger with higher wing loading...say a warbird.

I think a low winger's winger position relative to the ground eliminates ground effect, so it doesn't bounce as much.
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Old Oct 26, 2012, 03:03 AM
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You need to smooth those landings out itsme2, too fast, dropping to quick, etc, its good practice to get in some slow, slower, slower fly bys. Try flying the plane as slow as you can coming up your runway. Landing will be a little bit slower, don't rush the landing, give yourself plenty of slowdown room and fly it all the way till the wheels touch.
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Old Oct 26, 2012, 03:20 AM
Complete RC Idiot Savant
The Netherlands
Joined Nov 2009
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It all comes down to controlling your rate of descend to inches per second.

If you can land safely, you could try to make passes with the wheels say, 4 inches off the ground over the length of the runway, with colse to the minimum power that allows for level flight.

Once you get control over your rate of descend, just use that control to set down the wheels as soft as possible.

The problem with most novice pilots is, they either come in at idle and time their flare wrong, OR they come in slichtly over idle and determine the moment of touchdown with closing the throttle.
In both cases the wheels touch down while the rate of descend is increasing, leading to a bounce.

It is better to either come in on power and "fly it to the ground" or alternatively, come down in idle (controlling the glide path with slight and precise dosed shots of throttle) and pull a slight nose-up at exactly the right moment, to reduce rate of descend to zero at the moment of touch down.
Too early and the plane loses airspeed, starting to drop and here's nothing you can do=>bounce
Too late and, well.... rate of descend is not yet zero=>bounce.

It is all easier said than done, but practice makes perfect!

Brgds, Bert
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Old Oct 26, 2012, 05:07 AM
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Landing Bounce

There is such a thing as "in the groove" when it comes to landing.
Given enough room - -
Get close to the ground with enough throttle to maintain a "safe speed" and attitude. Back off the throttle to idle gently, and cut just before the wheels touch.

Or, Since a newbe really needs to be able to land "dead stick" with no power,
setup the approach with power at idle or off if electric. A bit fast is better than slow, until just above the ground. Adjust the rate of decent as needed to a reasonable speed and decent rate.

If the planes is flying towards you and you can see it well, you can look at the wings vs the horizon or any horizon like feature of the field. This helps with setting the decent rate, and you may even be able to judge the proper attitude from how much of the wing bottom is visible.

My DH-2 Beaver and Advance 25 are easy to land using a combination of these methods, with generally no bounce on short grass.
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Old Oct 27, 2012, 05:47 AM
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Contrary to what some others have suggested, my observation at our field is that many bouncy landings are caused by coming in too slow, which (a) makes the model less responsive to control inputs, and (b) makes it stall, hit the ground, and bounce up again one or more times.
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Old Oct 27, 2012, 09:39 AM
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United States, NJ, Newark
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Quote:
Originally Posted by abenn View Post
Contrary to what some others have suggested, my observation at our field is that many bouncy landings are caused by coming in too slow, which (a) makes the model less responsive to control inputs, and (b) makes it stall, hit the ground, and bounce up again one or more times.

An airplane should be stalled at touchdown. Note I said at touchdown, if you stall above the runway that's a different problem. Watch a bird land for an expert example of how it's done

As said by others, landing bounce is caused by too much speed. Too much speed is caused by too much "energy" on the approach. Or in other words, too much altitude or airspeed that has to be bled off. The best way to solve landing bounce is not voodoo over the runway, but to fly a better approach. So in short, it all starts on your downwind leg...if you even fly a pattern
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Old Oct 27, 2012, 12:25 PM
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United States, FL, DeLand
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Quote:
Originally Posted by rogue wolf View Post
An airplane should be stalled at touchdown.
That's not necessarily true. If you establish a flying height of an inch above the ground and reduce throttle you will land without bounce, provided you don't fly back upward again with up elevator. Even then it wouldn't be a bounce, it would be a touch and go!

Bounces happen because of too much vertical velocity when you touch down, not because of too much horizontal velocity. Therefore a bounce-free touchdown can happen at any velocity at which the plane has a sink rate instead of a climb rate.
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Old Oct 27, 2012, 12:51 PM
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Quote:
Originally Posted by Rockin Robbins View Post
Bounces happen because of too much vertical velocity when you touch down, not because of too much horizontal velocity. Therefore a bounce-free touchdown can happen at any velocity at which the plane has a sink rate instead of a climb rate.
This is true. However, different plane types and designs will have different rates of descent that will induce bounce or not. High wingers tend to bounce easier than low-wingers....in general based on my observation.
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Old Oct 27, 2012, 12:55 PM
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The Apprentice is prone to bouncing because the rear LG flex outward and the nose LG doesn't move, which points the plane upward, and if you have any speed, the thing is so light it will start flying again. The trick is to be at full elevator at touch down - that is the proper speed. Note that I denoted a landing speed by saying the elevator position.

You can also tie the wheels together to prevent them bending outward.
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