A new direction for an old thread: Crosswind landings

Bill Clinton, like him or not, is a shrewd fellow. When asked a
question that put his political life at risk, he made damn sure just
what the questioner meant. And the crux rested on "is." Now the more
astute of you will realize that "to be" is a tautology: state of being.
While some would think this a foundational word, a skilled speaker can
imbue it with all sorts of meaning, including confusing its tense.

If you understanding of flight depends on words (think back to your
time as a student), then should we be any less certain of the meaning
of those words since our lives may depend on them? Think of how many
times loose language in the cockpit led to accidents (take off power,
for example)... Why shouldn't equally loose language in textbooks be
just as hazardous?

Remember, it's winter. We can afford to look behind the words while we
wait for the weather to improve. (a norther point of view)

While I agree with the majority of Todd's post, it
would be beneficial to have some clarification on point
5.

T O D D P A T T I S T wrote:
5) If you slip while flying straight for very long,
you need
to lower the opposite wing or you will begin a skidding
turn. Modern gliders have a low fuselage side area
and take
a while to begin this type of skidding turn.

I know this may sound petty but considering how
this thread has evolved, it's appropriate.
Exactly what is your definition of 'flying straight'
and 'turn'? Remember what Clinton taught us about
something we thought was as simple as the word 'is'.


Apparently the consensus seems to be that there are
three types of crosswind landing techniqes used. Crab
or side slip or some combination of both. Would it
be commonly accepted to say that while using the same
spoiler setting for both a crab and a side slip crosswind
landing, that the glider side slipping will have a
higher rate of descent?

M Eiler

Quite recently a commercial glider applicant was asked to
demonstrate a slipping turn downwind to final, and do everything
including landing with no spoilers.

He did so, with the wing into the wind, but once he found himself
180 deg in the other direction, he forgot to "switch" the
slip to have the lowered wing into the wind. So it was a "bumpy"
landing with a crab.

So what is a slip? Well, a forward slip or side slip to
me is an uncordinated manuever where both wingtips
are at the same airspeed. A turning slip is when the
wingtips are at different airspeeds, and the uncoordinated
part means the low wing and the rudder are opposite (outside rudder).
If the rudder and low wing are the same, then it may be a skid.

If the ball and the low wing are the same, it's a slip, if the
ball and low wing are opposite, it's a skid.

Is that about right? Or have I missed something obvious?

In article ,
Martin Eiler wrote:
While I agree with the majority of Todd's post, it
would be beneficial to have some clarification on point
5.

T O D D P A T T I S T wrote:
5) If you slip while flying straight for very long,
you need
to lower the opposite wing or you will begin a skidding
turn. Modern gliders have a low fuselage side area
and take
a while to begin this type of skidding turn.

I know this may sound petty but considering how
this thread has evolved, it's appropriate.
Exactly what is your definition of 'flying straight'
and 'turn'? Remember what Clinton taught us about
something we thought was as simple as the word 'is'.


Apparently the consensus seems to be that there are
three types of crosswind landing techniqes used. Crab
or side slip or some combination of both. Would it
be commonly accepted to say that while using the same
spoiler setting for both a crab and a side slip crosswind
landing, that the glider side slipping will have a
higher rate of descent?

M Eiler





--

------------+
Mark J. Boyd

Or for that matter landing on the lee side of the runway...knowing
that the crosswind weather vaning is going to be steering
you back to centerline and over to the windward side.


fiveniner-Although I sorta understand your analysis,
I gotta say at some point this is going to be like
writing down on paper every variable in thermalling.


Stefan-My hope is that you are not an English as first
language guy...because your tone is not helping your
cause.



At 18:30 22 February 2005, 5z wrote:
It's interesting that everyone is talking about aligning
with the
centerline of the runway.

Why not set up a diagonal landing and thus reduce the
crosswind
component at touchdown.

Pilot's discussing engineering allways scare the be-jesus out of me.

The good thing is that the pilot does not need to understand physics
to fly, since 95% of the talk is complete BS, and the pilot's
still seem to manage the actual flying.

Toad

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

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 ;-)

Sorry Marty. I type at warp speed and don't always leave a name at the
end. For 17 years my contest ID was 59, thus the yahoo address. And
perhaps as a frequent contributor to the group, I've let my ego swell
to the point that I figure others will recognize me by content or
style.

Chris O'Callaghan
Ventus 2bx -- Oscar Charlie
Frederick, Maryland
Member of the Mid-Atlantic Soaring Association