Thread: Cessna v. Piper trainers
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Old 07-28-2009 | 05:29 PM
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3664shaken
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Originally Posted by Cubdriver
This is why low wing airplanes tend not to bounce, although they do tend to float.


Hmmmm, I have seen many bounced landings in low wing A/C, including the worst one ever in a Extra 300L.

There are many reasons an airplane bounces upon landing.

Too much airspeed.
Improper elevator application by the pilot.

Some landing gear is more prone to bounces then others. Piper uses oleo struts which dampen botched landings and result in less bounces. Cessna flat spring steel gear legs are particularly bounce prone while the tubular steel gear legs are less, they are still more bounce prone then oleo struts.

The other reason Cessna's may bounce more is the approach profile that is flown by them vs the Piper's approach.

In the Piper most CFI's instruct flying into ground effect, leveling off and then increasing attitude as the plane begins to fall out. The drawback with this method is nose gear first touchdowns in the beginning.

With Cessna's a round out is usually started at about 20 feet and when you enter ground effect you are already pitching for the flare. The drawback is if you are not managing speed and sink rate a higher than usual sink rate may occur, couple that with springy landing gear and the tendency for the student to pull back even harder and viola you have more bounces.

There is also one more reason why a low wing airplane tends to settle down and stick and this is due to their design and ground effect. Downwash normally reduces the angle at which the airstream hits the horizontal stabilator, when the airplane enters ground effect, downwash is reduced. This reduction in downwash increases the angle and gives the stabilator a higher (or less negative) AoA. This result is a small nose down pitching moment that decreases lift and gives the feeling of the low wing A/C sticking onto the runway. Of course the obvious resultant minor loss of lift also decreases the chances of a bounce.

Originally Posted by Cubdriver
Not at all correct... first of all, have you ever noticed that designers prefer a high-wing configuration for short field and STOL airplanes? Why, if there is so much more lift in ground effect would they do this?


There are a plethora of reasons that they choose high-wing aircraft but none of them have to do with ground effect, although there is one benefit but it is incidental.

First of all back-country A/C are conventional gear, low wing conventional gear would be suspect to hitting, rocks, shrubs, etc. Ever seen the flaps of a Piper, Mooney, Beech, etc, that has been landed on dirt strips, they are dinged up, hence you want/need your wings up high.

#2 the wing of a high -wing A/C is a complete lifting surface, from tip to tip therefore you can have a smaller wing for equal amount of lift, highly important in small spaces

#3 Forward and Down visibility is extremely important while scouting out the landing strip, nailing the landing and then taxing afterwards.

There are many more reasons, but ground effect is not one of them.

However, one good thing about a high wing A/C is that if they are overloaded they usually don't fly until they are able to. We have all seen videos or heard of stories about low-wing A/C struggling to get out of ground-effect when overloaded, or in high density altitude situations.

http://www.youtube.com/watch?v=gOaAZ1i2gNA

I could only imagine more of these incidents happening on backcountry strips if low-wing A/C were flown into them.
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