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bouncing off the runway



 
 
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  #11  
Old June 26th 08, 05:50 PM posted to rec.aviation.piloting
Robert M. Gary
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Posts: 2,767
Default bouncing off the runway

BTW: The tail can rise even after the wing is stalled.

-Robert
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  #13  
Old June 26th 08, 07:14 PM posted to rec.aviation.piloting
Ol Shy & Bashful
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Posts: 222
Default bouncing off the runway

On Jun 26, 11:49*am, "Robert M. Gary" wrote:
On Jun 26, 7:25*am, E Z Peaces wrote:

Doesn't a three-point landing occur at stall speed? *


That is one of the biggest myths in aviation. I've flown a lot of
taildraggers (GA) and few of them had the stall angle and the 3 pt
angle in alignment. As an example the Globe Swift stalls with the tail
about 2 feet off the ground while the Decathlon/Citabria stalls with
the tail on the ground and the mains still several feet in the air,
its very, very much still flying in the 3pt position. The hard part of
landing a Citabria is not to crush the mains after landing the tail.

-Robert, CFII


Bull****!
  #14  
Old June 26th 08, 07:32 PM posted to rec.aviation.piloting
Ol Shy & Bashful
external usenet poster
 
Posts: 222
Default bouncing off the runway

On Jun 25, 10:00*pm, E Z Peaces wrote:
Yesterday I chatted with a retired man flying a model airplane. *He said
he'd taken lessons in a plane with conventional gear in the 1950s. *On
his third lesson, the instructor had him land. *It was perfect.

After that, every time he landed he would bounce and float above the
runway. *His instructor didn't know what caused it. *A senior instructor
* went up with him and observed that when he touched down, he didn't
continue to hold the stick back. *That caused the tail to rise and the
plane to lift off.

That doesn't make sense to me. *I've always understood that with
conventional gear, excess speed is the cause of bouncing and floating.
With the main wheels forward of the center of mass, your angle of attack
will increase when you touch down, and the plane will rise if you still
have flying speed.

If a pilot touches down too fast, I've understood that he needs to keep
the tail up and use the brakes without nosing over.

If the instructor had told him he was touching down too fast because he
wasn't holding the stick back far enough during descent, that would make
sense to me because a higher angle of attack induces more drag.

The man said the problem was that he had failed to keep the stick back
after touchdown. *Does his recollection make sense?


Are you kidding? After nearly 60 years the recollections of a 3 hour
student have any validity? The VAST majority of botched landings are
due to flawed airspeed control and it doesn't matter what kind of
airplane. Many instructors fail to recognize that, or, fail to do
anything about it, especially when instructing. I see it all the time,
harp about it daily,and continue to mentor less experienced pilots on
this.
In the case of taildraggers specifically, if the airspeed and vertical
speed are not controlled, it will nearly guarantee a bounce with
predictable control problems. For a three point to be executed
properly, the airspeed MUST be near stall as in within Vso+ 5 mph or
less. Anything in excess of that must be dissapated during the flare/
roundout or touchdown and will result in an unpredictable touchdown
point.
Now, are you talking about a full stop landing? Then the touchdown
speed should be as low as possible. Are you talking about a gusty
cross wind? Then you have a different set of conditons to deal with.
Not to be a pushy butthead but I've got at least 6-7000 hours in
tailwheel aircraft crop dusting in a broad variety of aircraft
including twin engined and a lot of time instructing in them (couple
of thousand hrs..?)
taking a deep breath and just sitting back now .....
Ol S&B
p.s. I realize you were asking and not postulating so please don't
feel I was being gruff towards you personally?
  #15  
Old June 26th 08, 08:36 PM posted to rec.aviation.piloting
E Z Peaces
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Posts: 8
Default bouncing off the runway

Bertie the Bunyip wrote:
E Z Peaces wrote in
:

Bertie the Bunyip wrote:
More_Flaps wrote in
news:0390ffd1-a85e-4ae3-8971-
:

On Jun 26, 3:00 pm, E Z Peaces wrote:

The man said the problem was that he had failed to keep the stick
back after touchdown. Does his recollection make sense?
Nope


Does actually. Little tailfraggers, and big ones, come to think of
it, bounce along of you dont get the stick back after three pointing.
the mains will thrust it back up into the air a bit and then the nose
comes back down again repeating the cycle.



Bertie

Doesn't a three-point landing occur at stall speed?



Not always.


Isn't the plane
going too slowly to lift off again? Besides, if the tail is that low,
touching down won't increase the angle of attack, will it?


If the tail is that low, you have th estick all the way back.


The man said it was after touchdown that he'd quit holding the stick back.

You say the mains will thrust it back up into the air and the cycle
will repeat. In a three-point landing, it seems it would take springs
to make a plane rise. Aren't shock absorbers supposed to prevent
that?



Shock absorbers are for cars and they'r emade to dampen cycles such as
that.




Bertie


I've read about oleo aircraft struts at least as early as the 1920s.

Sorry about my multiple posts this morning. Each time I sent it, my
newsreader said the news server had not responded, so I'd try again.
  #16  
Old June 27th 08, 12:24 AM posted to rec.aviation.piloting
Bertie the Bunyip[_24_]
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Posts: 2,969
Default bouncing off the runway

E Z Peaces wrote in
:

Bertie the Bunyip wrote:
E Z Peaces wrote in
:

Bertie the Bunyip wrote:
More_Flaps wrote in
news:0390ffd1-a85e-4ae3-8971-
:

On Jun 26, 3:00 pm, E Z Peaces wrote:

The man said the problem was that he had failed to keep the stick
back after touchdown. Does his recollection make sense?
Nope


Does actually. Little tailfraggers, and big ones, come to think of
it, bounce along of you dont get the stick back after three
pointing. the mains will thrust it back up into the air a bit and
then the nose comes back down again repeating the cycle.



Bertie

Doesn't a three-point landing occur at stall speed?



Not always.


Isn't the plane
going too slowly to lift off again? Besides, if the tail is that
low, touching down won't increase the angle of attack, will it?


If the tail is that low, you have th estick all the way back.


The man said it was after touchdown that he'd quit holding the stick
back.




Yes, I know. I read your post.



You say the mains will thrust it back up into the air and the cycle
will repeat. In a three-point landing, it seems it would take
springs to make a plane rise. Aren't shock absorbers supposed to
prevent that?



Shock absorbers are for cars and they'r emade to dampen cycles such
as that.




Bertie


I've read about oleo aircraft struts at least as early as the 1920s.


Theyre not dampers, they're oleos and provide no damping. Shock
absorbers are something different and have a different function, though
tey're misnamed in any case, since its the springs that absorb and the
shicks, as they;'re called, prevent the energy stored in the spring from
rebounding the wheel off the road. Airplanes don't have shock absorbers.
  #18  
Old June 27th 08, 12:44 AM posted to rec.aviation.piloting
Robert M. Gary
external usenet poster
 
Posts: 2,767
Default bouncing off the runway

On Jun 26, 11:01*am, Bertie the Bunyip wrote:
"Robert M. Gary" wrote in news:bc1da0d3-1801-4602-8a5b-
:

On Jun 26, 7:25*am, E Z Peaces wrote:


Doesn't a three-point landing occur at stall speed? *


That is one of the biggest myths in aviation. I've flown a lot of
taildraggers (GA) and few of them had the stall angle and the 3 pt
angle in alignment. As an example the Globe Swift stalls with the tail
about 2 feet off the ground while the Decathlon/Citabria stalls with
the tail on the ground and the mains still several feet in the air,
its very, very much still flying in the 3pt position. The hard part of
landing a Citabria is not to crush the mains after landing the tail.


You're right about the Citabria, but not the Swift. The Swift's thing, like
a lot of low wing airplanes, is that the stab gets into roiled air as it
gets near the stall. As further evidence, the alpha on a swift in three
point is about 10 Degrees, no way you're going to have a critical angle
that low on anything this side of a razor blade.

Bertie


Maybe it depends on if you have the stall strips or not but mine would
go thunk on the mains with the stick all the way back and the tail was
no where near the ground. The Swift association would lecture pilots
not to 3 pt the Swift because of this. On the other hand I never flew
a plane that wheel landed as nicely as the Swift. It was like landing
a 172.

-Robert
  #19  
Old June 27th 08, 12:45 AM posted to rec.aviation.piloting
Robert M. Gary
external usenet poster
 
Posts: 2,767
Default bouncing off the runway

On Jun 26, 11:14*am, "Ol Shy & Bashful" wrote:
On Jun 26, 11:49*am, "Robert M. Gary" wrote:

On Jun 26, 7:25*am, E Z Peaces wrote:


Doesn't a three-point landing occur at stall speed? *


That is one of the biggest myths in aviation. I've flown a lot of
taildraggers (GA) and few of them had the stall angle and the 3 pt
angle in alignment. As an example the Globe Swift stalls with the tail
about 2 feet off the ground while the Decathlon/Citabria stalls with
the tail on the ground and the mains still several feet in the air,
its very, very much still flying in the 3pt position. The hard part of
landing a Citabria is not to crush the mains after landing the tail.


-Robert, CFII


Bull****!


I'll be happy to provide you a tailwheel checkout.

-Robert
  #20  
Old June 27th 08, 01:02 AM posted to rec.aviation.piloting
Bertie the Bunyip[_24_]
external usenet poster
 
Posts: 2,969
Default bouncing off the runway

"Robert M. Gary" wrote in
:

On Jun 26, 11:01*am, Bertie the Bunyip wrote:
"Robert M. Gary" wrote in
news:bc1da0d3-1801-4602-8a5b

-
:

On Jun 26, 7:25*am, E Z Peaces wrote:


Doesn't a three-point landing occur at stall speed? *


That is one of the biggest myths in aviation. I've flown a lot of
taildraggers (GA) and few of them had the stall angle and the 3 pt
angle in alignment. As an example the Globe Swift stalls with the
tail about 2 feet off the ground while the Decathlon/Citabria
stalls with the tail on the ground and the mains still several feet
in the air, its very, very much still flying in the 3pt position.
The hard part of landing a Citabria is not to crush the mains after
landing the tail.


You're right about the Citabria, but not the Swift. The Swift's
thing, li

ke
a lot of low wing airplanes, is that the stab gets into roiled air as
it gets near the stall. As further evidence, the alpha on a swift in
three point is about 10 Degrees, no way you're going to have a
critical angle that low on anything this side of a razor blade.

Bertie


Maybe it depends on if you have the stall strips or not but mine would
go thunk on the mains with the stick all the way back and the tail was
no where near the ground. The Swift association would lecture pilots
not to 3 pt the Swift because of this. On the other hand I never flew
a plane that wheel landed as nicely as the Swift. It was like landing
a 172.


It's the stab. Many low wing taildraggers have issues here. The Twin
Beech, for instance. You can three point it if you get it right, but if
you screw up and get it in the three point attitude when the mains are
more than about an inch off the ground, it will pitch forward and start
porpoising all over the place. The DC 3 as well. The Swift does the same
thing.

Bertie
 




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