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26-06-2008, 01:00 PM
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#1
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bouncing off the runway
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?
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26-06-2008, 01:54 PM
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#2
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Re: bouncing off the runway
On Jun 26, 3:00*pm, E Z Peaces <c...@invalid.invalid> wrote:
>
> The man said the problem was that he had failed to keep the stick back
> after touchdown. *Does his recollection make sense?
Nope
Cheers
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26-06-2008, 01:59 PM
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#3
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Re: bouncing off the runway
E Z Peaces <cash@invalid.invalid> wrote in news:g3v0og$d61$1
@registered.motzarella.org:
> 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?
>
Yep.
Bertie
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26-06-2008, 02:36 PM
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#4
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Re: bouncing off the runway
More_Flaps <Moreflaps@gmail.com> wrote in news:0390ffd1-a85e-4ae3-8971-
a9859f3558ae@g16g2000pri.googlegroups.com:
> On Jun 26, 3:00*pm, E Z Peaces <c...@invalid.invalid> 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
>
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26-06-2008, 04:34 PM
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#5
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Re: bouncing off the runway
On Jun 25, 8:00*pm, E Z Peaces <c...@invalid.invalid> 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.
You have to hold the stick back until you tie the plane down in order
to plant the little tailwheel on the ground. Without the stick back
not only do you have less steering but because it has so little weight
it could easily pop back up (if you push the stick forward right after
landing you could pop it up easily). In most light taildraggers one
person can easily lift the tail off the ground (which is how we would
move the plane, no tow bar required).
-Robert
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27-06-2008, 12:25 AM
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#6
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Re: bouncing off the runway
Bertie the Bunyip wrote:
> More_Flaps <Moreflaps@gmail.com> wrote in news:0390ffd1-a85e-4ae3-8971-
> a9859f3558ae@g16g2000pri.googlegroups.com:
>
>> On Jun 26, 3:00 pm, E Z Peaces <c...@invalid.invalid> 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? 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?
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?
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27-06-2008, 12:29 AM
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#7
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Re: bouncing off the runway
Bertie the Bunyip wrote:
> More_Flaps <Moreflaps@gmail.com> wrote in news:0390ffd1-a85e-4ae3-8971-
> a9859f3558ae@g16g2000pri.googlegroups.com:
>
>> On Jun 26, 3:00 pm, E Z Peaces <c...@invalid.invalid> 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? 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?
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?
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27-06-2008, 12:33 AM
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#8
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Re: bouncing off the runway
Bertie the Bunyip wrote:
> More_Flaps <Moreflaps@gmail.com> wrote in news:0390ffd1-a85e-4ae3-8971-
> a9859f3558ae@g16g2000pri.googlegroups.com:
>
>> On Jun 26, 3:00 pm, E Z Peaces <c...@invalid.invalid> 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? 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?
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?
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27-06-2008, 01:57 AM
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#9
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Re: bouncing off the runway
E Z Peaces <cash@invalid.invalid> wrote in
news:g408u4$k19$1@registered.motzarella.org:
> Bertie the Bunyip wrote:
>> More_Flaps <Moreflaps@gmail.com> wrote in
>> news:0390ffd1-a85e-4ae3-8971-
>> a9859f3558ae@g16g2000pri.googlegroups.com:
>>
>>> On Jun 26, 3:00 pm, E Z Peaces <c...@invalid.invalid> 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.
>
> 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
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27-06-2008, 02:49 AM
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#10
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Re: bouncing off the runway
On Jun 26, 7:25*am, E Z Peaces <c...@invalid.invalid> 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
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27-06-2008, 02:50 AM
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#11
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Re: bouncing off the runway
BTW: The tail can rise even after the wing is stalled.
-Robert
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27-06-2008, 04:01 AM
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#12
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Re: bouncing off the runway
"Robert M. Gary" <N7093v@gmail.com> wrote in news:bc1da0d3-1801-4602-8a5b-
011bae1790d2@v1g2000pra.googlegroups.com:
> On Jun 26, 7:25*am, E Z Peaces <c...@invalid.invalid> 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
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27-06-2008, 04:14 AM
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#13
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Re: bouncing off the runway
On Jun 26, 11:49*am, "Robert M. Gary" <N70...@gmail.com> wrote:
> On Jun 26, 7:25*am, E Z Peaces <c...@invalid.invalid> 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
Bullshit!
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27-06-2008, 04:32 AM
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#14
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Re: bouncing off the runway
On Jun 25, 10:00*pm, E Z Peaces <c...@invalid.invalid> 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?
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27-06-2008, 05:36 AM
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#15
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Re: bouncing off the runway
Bertie the Bunyip wrote:
> E Z Peaces <cash@invalid.invalid> wrote in
> news:g408u4$k19$1@registered.motzarella.org:
>
>> Bertie the Bunyip wrote:
>>> More_Flaps <Moreflaps@gmail.com> wrote in
>>> news:0390ffd1-a85e-4ae3-8971-
>>> a9859f3558ae@g16g2000pri.googlegroups.com:
>>>
>>>> On Jun 26, 3:00 pm, E Z Peaces <c...@invalid.invalid> 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.
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