A new direction for an old thread: Crosswind landings

Ah, but the side slip confuses this. In order to change your ground
track by 20 degrees, you need to change your direction through the
airmass by 20 degerees. No argument there I'll guess. But your question
is, why do we care? Because a turn to final that includes a side slip
at the end gives a false impression of which way the aircraft is really
going. In fact, there's no reason to align track and heading until
touchdown. We've already discussed why you might choose not to.

Clearly many pilots get this. But many more do not. Though I suspect
they are becoming less certain about their own notions of how this
stuff works.

If the deconstructions are too simplistic (or obvious), I'd argue that
it's needed. I quoted the Soaring Flight Manual earlier to demonstrate
that even our textbooks promote some questionable notions of flight.
(I'll offer some more examples later this week.) Remember my question:
are crabs and side slips additive? Why would you NEED both in a strong
crosswind? If you think they ARE additive, I'd like to understand how
and why.

As for the art of flight (your last few sentences), I'd counter that
any maneuver that we cannot adequately (and simply) deconstruct,
shouldn't be in our repertoire. Why? Because when things go wrong, as
they sometimes do, you may not have the "rote" skills to quickly and
effectively correct them. Remember, we're doing these maneuvers
infrequently, near the ground, in turbulence. Not a forgiving
environment.

If I'm digging deep, it's so I can backfill with a better grade of
soil. I'd like to condense this down to several paragraphs, but getting
it short takes time and effort and a lot of words. If, on the other
hand, you have a concise, accurate description, please share it.

Interesting. But I think what you're saying is that many pilots feel
uncomfortable lowering the wing enough to fully align the gear with
their ground track, so when they land, they still need to skid the
fuselage around. I suppose this makes the flare a little less dramatic,
and therefore less error prone. And keeps the lowered wing a
comfortable distance above the ground. My quibble then is only with how
you describe. I don't think you combine a side slip with a crab: this
gets back to that implication that they are somehow additive. Instead,
you are combining a side slip with a pretouchdown skid. The primary
advantage is that you get a more wholesom view of the runway on final.
The disadvantage is that you have less yaw authority to swing the
glider during the flair. (Remember the ailerons have some effect as
well. You can increase the rate of yaw significantly with crossed
controls: kicking down wind while lowering the upwind wing as you
flare.)

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.

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)

On 22 Feb 2005 16:22:06 -0800, wrote:

I've seen quite a few. And the reason to have the discussion is because
competent pilots continue to break themselves and their gliders as a
result of pilot error. Why? Well, we're exploring one avenue. You are
welcome to help us or not.

I'm afraid that I can't be any help here.
The only thing I know about crosswind landings is to crab and (during
the flare) to align with the runway with the rudder, wings level.

To me this is such a natural maneuvre that I happen to be unable to
see why there is a need to discuss this matter - but obviously others
see things in a different way.




Bye
Andreas

Pretty cool.

Bryan

wrote in message
oups.com...
Ok here is a little video gem for you all....in the middle of this
video

http://www.silentflight.com/movies/silentflight.wmv

there is a crosswind landing (30 degree + in 20+ knots of wind) in my
ASW22.

Big Plane, Big wind, Big crosswind angle.

Note the yaw string in the incockpit footage.

enjoy...

Al

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

Could you quote the poster you are replying too? At least the portion
you are replying to? The length of the
thread is making it very difficult to know what you are replying to.

wrote:
Interesting. But I think what you're saying is that many pilots feel
uncomfortable lowering the wing enough to fully align the gear with
their ground track, so when they land, they still need to skid the
fuselage around. I suppose this makes the flare a little less
dramatic, and therefore less error prone. And keeps the lowered wing
a comfortable distance above the ground. My quibble then is only with
how you describe. I don't think you combine a side slip with a crab:
this gets back to that implication that they are somehow additive.
Instead, you are combining a side slip with a pretouchdown skid. The
primary advantage is that you get a more wholesom view of the runway
on final. The disadvantage is that you have less yaw authority to
swing the glider during the flair. (Remember the ailerons have some
effect as well. You can increase the rate of yaw significantly with
crossed controls: kicking down wind while lowering the upwind wing as
you flare.)



--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Why would anyone use a sideslip instead of a crab during
landing? I've always thought it was to avoid sideloading the
tire (or tires) and thereby causing them to
go flat.

This is also why I like grass or dirt runways for students.
If they mess up the sideslip, then the side load is still
"detectable" but doesn't damage anything. I could see how
pilots of long-winged low-wing gliders might like grass or
dirt too, so they can land wings level in a crab. The guy who posted
that he does this on a narrow runway with obstructions
sounds like he's cuttin' it pretty close. :O

I prefer to teach the side slip technique, because it seems
less dynamic to me. It seems like a more stabilized approach,
since the sight picture doesn't dramatically change right at
touchdown. The guys who say crab and then straighten it right at
touchdown are doing something quite dynamic at the last second,
which isn't my preference. Also, at that last second on touchdown,
if it's a cement runway, they are putting at least some side load on the
tire, whether it is going sideways during touchdown or whether
they touch down and then are turning during rollout. If the wings
are really that long you have to do this, then I guess you
gotta do what you gotta do.

If the wind is really that strong, the ground roll will be shorter
too, so that helps the crabbing guys a bit. Even a direct crosswind
gets some headwind component in a 20 degree crab, right?

I also fly stuff that has SOME dihedral, and haven't flown anything over
20 meters, and I haven't flown a Pegasus (which some of you say
has flexing wings) so I haven't even ever seen a windward wing need to
be dropped below the gear in a full forward slip with the fuselage
straight down the runway. I have run out of rudder, and run out of
aileron before, in both power and gliders, and have landed with
both crab and sideslip due to this. Then I've benignly run off the
side of the runways/strips. In each of these cases there was
extra "room" to breathe, with no runway lights or signs, etc, just dirt.

Is a sideslip the only way to do it? No. If I feared catching a wingtip
would I land in a crab? Yes. I'd rather shear off the tire than
groundloop. If I could find grass or dirt, though, I think
I'd prefer that.

I've found that sideslips are also really challenging for new students.
They have a little trouble conceiving crossed-controls until they've
practiced it quite a bit. I found that I too wasn't able to
do a crosswind landing to the full crosswind component until
I had several hundreds of hours. Partly because I just wasn't
exposed to that heavy of crosswinds until then.

I try to set up a stabilized final approach at 400ft or so.
If it looks like I'm gonna run out of rudder or aileron in that
stabilized descent with a ground track straight down the runway
in a sideslip, then I make other plans. If the runway is wide, then
land diagonally. If there is a spot that allows me to go off the
runway weathervaning, then land at that spot (if the wind is that
strong I'm not gonna roll very far anyway).

My main concern is that if I barely have enough control authority
at approach speed, then the controls won't be able to hold that
slip when my airspeed decreases on rollout. To some degree
the wind gets a little lighter as I descend, however, so
if I can see the sock isn't as fierce as what I see at
400 ft, the lesser control authority on rollout may be enough
with the lighter wind.

Lots of stuff going on! And yes, practice makes perfect.
In conclusion, this is maybe a little more related to
"expense" and not "safety" as a botched crosswind landing on the
runway can certainly cost some serious $$$$s, but I'm not aware
of glider fatalities from botched runway crosswind landings.
Off field landings are perhaps another story...and of course
there could be crosswind there too...but somebody else will
need to talk about those intelligently...

In article .com,
wrote:
Ah, but the side slip confuses this. In order to change your ground
track by 20 degrees, you need to change your direction through the
airmass by 20 degerees. No argument there I'll guess. But your question
is, why do we care? Because a turn to final that includes a side slip
at the end gives a false impression of which way the aircraft is really
going. In fact, there's no reason to align track and heading until
touchdown. We've already discussed why you might choose not to.

Clearly many pilots get this. But many more do not. Though I suspect
they are becoming less certain about their own notions of how this
stuff works.

If the deconstructions are too simplistic (or obvious), I'd argue that
it's needed. I quoted the Soaring Flight Manual earlier to demonstrate
that even our textbooks promote some questionable notions of flight.
(I'll offer some more examples later this week.) Remember my question:
are crabs and side slips additive? Why would you NEED both in a strong
crosswind? If you think they ARE additive, I'd like to understand how
and why.

As for the art of flight (your last few sentences), I'd counter that
any maneuver that we cannot adequately (and simply) deconstruct,
shouldn't be in our repertoire. Why? Because when things go wrong, as
they sometimes do, you may not have the "rote" skills to quickly and
effectively correct them. Remember, we're doing these maneuvers
infrequently, near the ground, in turbulence. Not a forgiving
environment.

If I'm digging deep, it's so I can backfill with a better grade of
soil. I'd like to condense this down to several paragraphs, but getting
it short takes time and effort and a lot of words. If, on the other
hand, you have a concise, accurate description, please share it.



--

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

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