A new direction for an old thread: Crosswind landings

Martin, you are entirely wrong. I'm not obsessed. Really. No, I mean
it. ;-)

I use slips as a matter of course because I understand their USE and
RISKS and I am competent. What I am obsessed with is finding the
language that will let me explain clearly, succinctly, that crabbing
and slipping are not means to the same end. Perhaps I should refocus
attention on the word crabbing... which give the impression that it is
a maneuver as opposed to being normal wings level flight. Maybe the
better way to discuss this is to talk about approaches being
coordinated or uncoordinated.

We all agree that in order to transition to the ground in a crosswind
situation, we must move from coordinated to uncoordinated flight. You
have a choice when to apply controls to establish uncoordinated flight.
You can do it just before touch down (in which case the turn that
accompanies a skid is manageable), or you may do it earlier on final.
What I want to knock down is this notion of either a crab or a slip as
it infects our understanding of the purpose of the slip.

In order to establish a new ground track, you must turn. A side slip is
not a turn. All forces are balanced. As I've already described, many
pilots are confused about this difference. They explain that the side
slip works because the tilted left vector points into the crosswind,
dragging the glider sideways and compensating for wind drift. This
works in practice, but is wrong in fact because the tilted lift vector
is exactly matched by fuselage drag. If there were an unbalance force,
the glider's direction would continue to change... that is, circle. The
point is to find a better way of saying this. The place I'm trying to
get to is that when we compensate for crosswind on final, what we are
really doing when we initiate the side slip is a turn... what is in the
first instant a coordinated turn (remember which way the nose goes if
we don't use coordinating rudder while we roll into the bank), which
becomes a slipped turn as we reverse the progressively rudder against
the turn to keep heading aligned with runway, until we reach a beta
where the wing turning force is exactly compensated by the fuselage
force.

A better way to teach this and practice it is to keep the turn
coordinated until the desired ground track is achieved. This
demonstrates clearly the only way to establish a new ground track... by
turning to what we typcially call a crabbed approach. Then, at the
pilot's option, he may enter a slip, which will align the gliders
heading with its ground track. This crearly demonstrates that the
slip's only purpuse is alignment, just as the only purpose for the
rudder kick before touchdown is alignment (the only purpose of which is
to reduce side loading on the gear). The advantage of the slip is that,
unlike the rudder kick, all foreces are balanced. If the touch down is
delayed, you are much less likely to have to make large corrections in
direction.

In your experience, how many pilots stick with this sport. I've heard
commercial operators say it's about 1 in 5. Twenty percent get it.
Eighty percent don't. And of the 20% that get, how many really get it?

I already know how to do it. Now I'm trying to "get it" in a way that I
can easily explain, and maybe help that other 80% figure things out.

Martin Eiler wrote:
The following is a snip from one of Fiveniner's
early posts regarding the use of side slips for
dealing with wind drift while on final.

At 00:00 20 February 2005,
wrote:
But the notion that the tilted lift vector is compensating
for
wind drift is flawed. Useful, but flawed.

Having read all of his posts in this thread, it is
apparent that he has supplied no real data
capable of substantiating his position that side
slips cannot compensate for wind drift. Yes,
there is a portion of the soaring community
that are die-hard crab pilots. That does not
mean that their choice automatically validates
his opinion that side slips can't compensate for
cross wind. Those pilots who are experienced
with side slips seem to agree with the SSA's
Soaring Manual, in that a side slip does have
some limitations, and consequently at some point,
some amount of crab may be needed to be added
to the side slip to achieve the desired result.

Interestingly, after rereading his other posts, it
becomes quite obvious that he is obsessed with
the opinion that pilots should only be allowed to
fly coordinated while at or below pattern altitude.
Although he is entitled to his opinion, few other
pilots would support the concept that a pilot who
intentionally flies uncoordinated on final is operating
dangerously.

Generally speaking having lofty ideals is admirable,
however it is more warmly accepted when an
individual signs his post with his real name.

M Eiler

Still, Martin's point stands - you don't sign with your name.

And the whole thing somehow looks pretty much like intellectual
masturbation. Getting a ship onto a runway in a crosswind isn't the most
diffult thing in flying glider, and if a student doesn' get it, he wouldn't
get a number of things anyway.

--
Bert Willing

ASW20 "TW"


a écrit dans le message de news:
...
Martin, you are entirely wrong. I'm not obsessed. Really. No, I mean
it. ;-)

I use slips as a matter of course because I understand their USE and
RISKS and I am competent. What I am obsessed with is finding the
language that will let me explain clearly, succinctly, that crabbing
and slipping are not means to the same end. Perhaps I should refocus
attention on the word crabbing... which give the impression that it is
a maneuver as opposed to being normal wings level flight. Maybe the
better way to discuss this is to talk about approaches being
coordinated or uncoordinated.

We all agree that in order to transition to the ground in a crosswind
situation, we must move from coordinated to uncoordinated flight. You
have a choice when to apply controls to establish uncoordinated flight.
You can do it just before touch down (in which case the turn that
accompanies a skid is manageable), or you may do it earlier on final.
What I want to knock down is this notion of either a crab or a slip as
it infects our understanding of the purpose of the slip.

In order to establish a new ground track, you must turn. A side slip is
not a turn. All forces are balanced. As I've already described, many
pilots are confused about this difference. They explain that the side
slip works because the tilted left vector points into the crosswind,
dragging the glider sideways and compensating for wind drift. This
works in practice, but is wrong in fact because the tilted lift vector
is exactly matched by fuselage drag. If there were an unbalance force,
the glider's direction would continue to change... that is, circle. The
point is to find a better way of saying this. The place I'm trying to
get to is that when we compensate for crosswind on final, what we are
really doing when we initiate the side slip is a turn... what is in the
first instant a coordinated turn (remember which way the nose goes if
we don't use coordinating rudder while we roll into the bank), which
becomes a slipped turn as we reverse the progressively rudder against
the turn to keep heading aligned with runway, until we reach a beta
where the wing turning force is exactly compensated by the fuselage
force.

A better way to teach this and practice it is to keep the turn
coordinated until the desired ground track is achieved. This
demonstrates clearly the only way to establish a new ground track... by
turning to what we typcially call a crabbed approach. Then, at the
pilot's option, he may enter a slip, which will align the gliders
heading with its ground track. This crearly demonstrates that the
slip's only purpuse is alignment, just as the only purpose for the
rudder kick before touchdown is alignment (the only purpose of which is
to reduce side loading on the gear). The advantage of the slip is that,
unlike the rudder kick, all foreces are balanced. If the touch down is
delayed, you are much less likely to have to make large corrections in
direction.

In your experience, how many pilots stick with this sport. I've heard
commercial operators say it's about 1 in 5. Twenty percent get it.
Eighty percent don't. And of the 20% that get, how many really get it?

I already know how to do it. Now I'm trying to "get it" in a way that I
can easily explain, and maybe help that other 80% figure things out.

Martin Eiler wrote:
The following is a snip from one of Fiveniner's
early posts regarding the use of side slips for
dealing with wind drift while on final.

At 00:00 20 February 2005,
wrote:
But the notion that the tilted lift vector is compensating
for
wind drift is flawed. Useful, but flawed.

Having read all of his posts in this thread, it is
apparent that he has supplied no real data
capable of substantiating his position that side
slips cannot compensate for wind drift. Yes,
there is a portion of the soaring community
that are die-hard crab pilots. That does not
mean that their choice automatically validates
his opinion that side slips can't compensate for
cross wind. Those pilots who are experienced
with side slips seem to agree with the SSA's
Soaring Manual, in that a side slip does have
some limitations, and consequently at some point,
some amount of crab may be needed to be added
to the side slip to achieve the desired result.

Interestingly, after rereading his other posts, it
becomes quite obvious that he is obsessed with
the opinion that pilots should only be allowed to
fly coordinated while at or below pattern altitude.
Although he is entitled to his opinion, few other
pilots would support the concept that a pilot who
intentionally flies uncoordinated on final is operating
dangerously.

Generally speaking having lofty ideals is admirable,
however it is more warmly accepted when an
individual signs his post with his real name.

M Eiler

.... that the slip's only purpuse is alignment, just as the only purpose
for the
rudder kick before touchdown is alignment (the only purpose of which is

to reduce side loading on the gear). The advantage of the slip is that,

unlike the rudder kick, all foreces are balanced.

... etcetera
... etcetera

it is not that complex.
or that subtle
approaching it with the "it is hard to understand" attitude maybe one
reason why
the pilots at your club go all "eyes glaze over" when you offer to run
through the 'subtleties of the slip/crab interaction at point of
flight/landing interface' with them 'just one more time'.

p.s. why not discuss ground erffect again - I *love* that one.

- what I know about ground effect from things pilots have told me:
* the vortex at the tips gets cut in half so the drag is reduced
* list improved relative to the 'thicker' air squashed under the wings

hello & love to all who rig and then de-rig without flying

jonny.

Jonny.

Jonny ;-)