A new direction for an old thread: Crosswind landings

Oups - I take back my first remark.

--
Bert Willing

ASW20 "TW"


a écrit dans le message de news:
...
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

OK. I think this thread has served its purpose, at least for me. It
looks like the key may be centered on "coordination."

Might I suggest to active instructors that you try my exercise and
report back: coordinated turn to a heading that establishes ground
track as you would at altitude, the entry and recovery from a slip to
demonstrate gear alignment and return to wings level coordinated
flight. You might preface this with a forward slip demonstration in
light winds and comment on the misalignment of the gear with the runway
and the need to align before touch down. When might this misalignment
be useful? Let the student mull that over... then start talking about
crosswind navigation and see if he makes the connection.

I'm checking out for the next week. If someone has an epiphany, please
copy me back channel.

Cheers,

Chris O'Callaghan

At 18:30 25 February 2005,
wrote:
Yes, well said. But still wrong, in this sense:

Most of us mere mortals are very broad minded about
this; why don't you just fly the bleedin' picture as
it changes!

is that Zeb?
jon gogan

At 06:00 26 February 2005, Eric Greenwell wrote:
I start using crab when I'm close to full rudder in
the
side-slip, which can happen in strong cross winds.
The low wing still seems sufficiently high at that
point,
but I don't have a measurement for the angle it makes
with the ground.

Regardless, it's very rare that I've had to land where
the height of the grass or bushes was a concern.
If I routinely landed where the wing tips were over
20'-30' high grass, perhaps I'd be using a crab instead.

Here's some interesting data. ASK-21's have quite
a bit of dihedral and relatively stiff wings as
compared to most fiberglass single place gliders.
A K-21 pilot landing with the upwind wing leading
edge parallel to the ground has a 3.5 degree bank.
If he was foolhardy enough to touch down with the
main wheel and upwind wing at the same time,
he would be in a 6.5 degree bank. So it might
seem reasonable to expect that a pilot proficient
in side slips would therefore maybe be willing to
touch down with a 5 degree bank.
M Eiler

It would appear that there has been confusion over
track and heading, I know you have susssed it Todd
but others may not.

If we consider the relative airflow in the horizontal,
Ignoring the vertical, it is simple. With the wings
level the relative airflow is straight down the fuselage,
the string is in the middle. With a slipping approach
the relative airflow is at an angle from the side of
the lowered wing, the string will be blowing away from
the lowered wing. The aircraft is balanced as you say.

In both cases the track over the ground will, if we
have got it right be lined up with the runway centreline/direction
What puzzles me is that we fly around all day using
the first method to achieve our required track, why
complicate things near the ground.


At 19:30 28 February 2005, T O D D P A T T I S T wrote:
Why not just say that in a crosswind landing, on
final, you
always have to fly an upwind course through the air
to
achieve a ground track aligned with the runway.
Always.

'J.A.M.' wrote:
Because it is not true...

Obviously I lack the ability to explain myself well
enough to be understood.

You are doing fine - better than my Spanish, which
is the
closest I can come to a second language :-)

You see, english is not my craddle language, and I
am having some trouble
with it...
And from other posts, as the one you don't see how
a slip on base will get
you a longer final, I'm afraid that we have some confusion
going here about
the manouever discussed. Maybe we are talking about
different manouevers.

Perhaps

I'll try to make a diagram (one image is worth a thousand
words...) and post
it somewhere.

Just for this one, I'll fall, though...
Imagine a runway, a left crosswind, for example, and
you trying to land. If
your fuselage is aligned with the runway the wind will
blow you to the right
of the centerline.

That's clear.

You can turn left, into the wind, and then compensate
as
you say. Your nose will point left of the runway, and
your ground track
(velocity vector) will be aligned with the runway.

Correct - we agree. At this point, your flight through
the
air is angled to the left of the runway to achieve
the
ground track carrying you straight to the runway, or
as I
originally wrote, you are flying 'an upwind course
through
the air to achieve a ground track aligned with the
runway.'

Or you can put the left wing down. The glider will
try to turn to the left
(uncoordinated), but then you, as a savvy pilot, push
the right rudder to
mantain the fuselage aligned with the runway.

Correct. This is the upwind wing down slipping approach.
The first was the level wings, nose pointed upwind,
crabbing
approach.

Well, now we are aligned with the runway, wind wing
(left) down, right
rudder to mantain alignment...

We are in agreement to here.

the wind drift now is compensated with the
lateral force produced by the banked wings.

But here we disagree. The drift is not stopped by
'lateral
force produced by the banked wings.' It is stopped
because
you are flying a course upwind. You are confused with
exactly the confusion that the original poster felt
was a
problem. Lowering the upwind wing does not oppose
the wind
with a force. The force produced by the wing is countered
by an opposite force produced by the fuselage that
is flying
at an angle to the direction of motion. The direction
of
motion is upwind relative to the air to achieve motion
over
the ground straight towards the runway.

So you are not turning upwind as
you suggest,

Yes, you are. You suffer from the same misunderstanding
that started this thread - a belief that the lowered
upwind
wing produces an unbalanced force. It does not..
You can
see that by considering that you can fly straight towards
the runway in a slip when there is no crosswind, only
by
pointing the fuselage to the side. When slipping the
direction you are going through the air is never aligned
with the fuselage.

and your ground track is aligned with the runway. Voila!!!

Think carefully again.

When you are closer to the ground as to concern you,
reduce the bank and the
rudder as fit. It'll be for a few seconds anyway.
I've used this technique many times.

So have I. It is not the technique that is wrong,
just your
understanding of the aerodynamics.

I have also induced severe slips to
augment my descent rate and make for steeper approaches
into short fields
(outlandings) and with obstacles.

And when you did that, you should have noticed that
your
nose was pointed to the side of the direction you were
actually traveling.

Anyway it's sunny outside, I'll be flying again soon!
Suggest you to do the
same.

It's getting closer to that time - can't wait.

Todd P. Wrote: "Forward slips to either side are not skids. In a typical
left pattern, this would be left rudder and right
aileron/wing down on base. "

Just checking...but do you mean that in a left pattern, you reccomend
turning to the left, then rolling the aircraft into a slip the opposite
direction?? If you do, I think that is wrong. I fly most of my patterns with
a more rounded base and final and if I were in a left pattern, slipping in
a turn to final to the left, the rudder would be nearly neutral or slightly
biased to the right, and the left wing would be down...Opposite of what you
wrote...

Am I confused here..??


Steve.