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.



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Mark J. Boyd