A new direction for an old thread: Crosswind landings

On 24 Feb 2005 09:33:40 -0800, wrote:


The most succinct advice I've seen in this thread is "Geez, just do
it!" My sentiments exactly. But not very helpful for a confused pilot.
Wouldn't we prefer that new pilots apply knowledge rather than muscle
memory?

Well... I've got a couple to thousands flights, most of them as
instructor. But I have to admit that I'm being very confused over this
discussion. I gave up trying to follow the more technical aspects
(like these forward slips and sideslips.. lol. How glad I am that this
difference doesn't exists in the German language.).

Why make things more difficult than they are? In my opinion this
thread is beating a dead horse.

Of course it's essential for a student pilot to know his basics - but
why tell them about all aspects of a topic if they only need to know
some "how-to" 's?
For most things there's more than one way to accomplish them, but it's
not required to know all of them, don't you agree?



I pointed out at the top of this thread that it is confusing to tell a
pilot that he can either "crab" or "side slip" on crosswind final. It
gives the impression that these are two separate maneuvers that produce
similar effects. And that used together, their effects are somehow
additive. They are neither similar nor additive. We should find a way
to clear this up and make it part of our methodolgy for introducing and
practicing crosswind landings.

Simple. Teach the guys to grab and use their rudder during the flare.
Period.
Seems to work like a charm for *any* glider on my side of the pond
which is by far the majority of the gliders in the world.
very big grin.



Bye
Andreas

wrote:
...
Why would you NEED both in a strong
crosswind? If you think they ARE additive, I'd like to understand how
and why.

You don't NEED both. You can achieve the needed angle between ground track
and direction of airspeed just by using crabbing, since there is no limit
to the angle you can obtain by crabbing. However if your mind is to use
slipping there is a limit to the angle that can be achieved by slipping,
if you think the thing to its extreme, when slipping with a 90 degrees
bank the useful angle is reverted to zero, so there is a maximum somewhere.
So if the crosswind is so strong that the needed angle exceeds this maximum,
even if you want to use slipping, you have to add some crabbing, in this
sense slipping and crabbing are additive, i.e. the resulting angle may be
due partly to slip and partly to crab if both are used.

T o d d P a t t i s t wrote:
Touching down in a slip has nothing to do with making
landings "simpler."

No. But approaching in a slip does.

...If you don't understand why a slip is
needed in a crosswind, then you don't understand the
aerodynamics involved.

Probably true but I was actually discussing the approach technique, not
the landing. I assumed we all understood that the variations being
discussed were in the approach, not in the touchdown - especially since
the turn from base to final (a fair way before touchdown) has figured
prominently in your and 59yahoo's discussion. Sorry if I confused you
but I must say the aim of 59yahoo's rambling essays has confused me.

...
it seems to work for them. Like you, I was only ever taught crabbed
landings.

If you only know crabbed landings, then you will land
sideways every time. That's just the reality of the
physics. In a high crosswind on a hard surface, landing
crabbed is very bad.

Sorry. "crabbed landings" was intended as shorthand for "crabbed
approach to landing in a crosswind". I hope you were the only one
confused but I'm glad to sort it out.

I seriously doubt that you were taught to land crabbed.
Most likely you were taught to use a combination of last
minute rudder to align with the runway (that ,maneuver puts
you in a slip just before touchdown) and to carefully keep
the upwind wing no higher than the downwind wing.

Interestingly, the most common accident or incident "during the rollout
following a crosswind landing" (so I don't confuse anyone) is ground
contact by the UPWIND wing or pod.

GC

J.A.M. wrote:

It would only take me a flight to explain it (to show, really) but I'm
afraid that I can't be more clear writing!
If I'm still unclear I'll try to elaborate more.

Don't waste your life, Jose. He understands you perfectly well.
They're playing language games. It's got nothing to do with actually
flying gliders.

escribió en el mensaje

"Slip to CONTROL crosswind."
This is confusing. How does the slip control crosswind?
Next, "wings level..." Does that mean the rudder is brought to neutral?

He's just a pedantic ****ant.

He probably understands "semiotics". Language games can take several forms!

GC

Graeme Cant wrote:
The explanation may lie in the widespread use of Schweizer 2-33s in the
US whose high wing allows wing-down landings - and it works even better
than a Cezzna because it only has one main wheel and it slows down
quickly. Since the technique is a bit doubtful with the more common
mid-wing, high aspect ratio gliders that many pilots will move to, it
seems silly to teach it in the first place but that's their business and
it seems to work for them. Like you, I was only ever taught crabbed
landings.

Perhaps that is why the a side-slipped landing seems "doubtful" to you?
If you had training and experience in the technique, it might seem as
sensible and as easy as it does to me. I was trained in an ASK 13, I've
flown the usual fiberglass ships for 1000's of hours, and I've used both
techniques. After a while, found I preferred a side-slip to a crab; even
so, I still use some crab in a strong crosswind.

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

Eric Greenwell
Washington State
USA

If the cross wind is straight across the runway and strong enough you
can crab 90 degrees and land vertically, like a helicopter. Though I've
never actually done this I have "parked" a 1-26 above the middle of the
field at 1,500 feet and descended vertically to pattern altitude before
putting the nose down and proceeding. Of course, folks "park" in wave
all of the time.

Al


Robert Ehrlich wrote:
wrote:

...
Why would you NEED both in a strong
crosswind? If you think they ARE additive, I'd like to understand how
and why.


You don't NEED both. You can achieve the needed angle between ground track
and direction of airspeed just by using crabbing, since there is no limit
to the angle you can obtain by crabbing. However if your mind is to use
slipping there is a limit to the angle that can be achieved by slipping,
if you think the thing to its extreme, when slipping with a 90 degrees
bank the useful angle is reverted to zero, so there is a maximum somewhere.
So if the crosswind is so strong that the needed angle exceeds this maximum,
even if you want to use slipping, you have to add some crabbing, in this
sense slipping and crabbing are additive, i.e. the resulting angle may be
due partly to slip and partly to crab if both are used.

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

When I said straight I meant aligned with the runway axis, and with the
fuselage as well (in a slip).

"T o d d P a t t i s t" escribió en el
mensaje news
"J.A.M." wrote:

Ok... When the sailplane is under crosswind, it's velocity vector is
altered
and it's not folowing a straight course over ground.

If the crosswind is constant and the sailplane is flying
constant speed and heading, the ground track is straight.
The problem is that the straight ground track may not be
aligned with the runway. If it's not, you must turn to a
new heading.

To compensate for this
you change the direction of the lift vector sideways (rolling the wings
with
ailerons) while keeping the nose pointed where you want (opposite rudder,
a
slip).

Banking the wings and changing the lift vector produces a
side force in the direction you are banked. Pointing the
nose opposite the banked wings produces an opposing force
due to the angle of attack of the fuselage. These two
effect balance out and the track remains straight.

This changes the velocity vector of the glider,

The velocity vector changes only if the pilot delays the
opposite rudder enough to allow the uncompensated bank to
turn the glider, change the track and compensate for the
wind. If the pilot was initially crabbing sufficiently,
then he would not delay the opposite rudder and the glider
would not turn, the track would remain unchanged, and the
only difference would be the increased descent rate and the
fuselage would now be aligned with the runway.

making it follow a straight course over ground,

It's always straight, during crab and slip.

but a somewhat uncoordinated flight in the airmass (in a
slip, the velocity vector is not aligned with the fuselage; the glider
does
not flies straight).

Correct.

Wings level means... wings level... angle of bank zero, level with the
horizon, horizontal. I'm sorry I'm unable to explain better. The rudder
goes
where it needs to go to keep the string centered (coordinated)

Are you saying you land wings level in a crosswind, your
wheel is aligned with the runway AND your yaw string is
straight (coordinated flight)? It just isn't possible.

The glider is not skidding, it's just between a skid and a crab.

I have no idea what this is supposed to mean. If your yaw
string is straight, you are crabbed. If it's off to the
side, you are either slipping or skidding.

You seem to be confused about the exact issue that drives
this discussion.

I thought that with a 1-26, that's actually how they operate even at 0 wind
:-))))

--
Bert Willing

ASW20 "TW"


"Albert Gold" a écrit dans le message de news:
...
If the cross wind is straight across the runway and strong enough you can
crab 90 degrees and land vertically, like a helicopter. Though I've never
actually done this I have "parked" a 1-26 above the middle of the field at
1,500 feet and descended vertically to pattern altitude before putting the
nose down and proceeding. Of course, folks "park" in wave all of the time.

Al


Robert Ehrlich wrote:
wrote:

...
Why would you NEED both in a strong
crosswind? If you think they ARE additive, I'd like to understand how
and why.


You don't NEED both. You can achieve the needed angle between ground
track
and direction of airspeed just by using crabbing, since there is no limit
to the angle you can obtain by crabbing. However if your mind is to use
slipping there is a limit to the angle that can be achieved by slipping,
if you think the thing to its extreme, when slipping with a 90 degrees
bank the useful angle is reverted to zero, so there is a maximum
somewhere.
So if the crosswind is so strong that the needed angle exceeds this
maximum,
even if you want to use slipping, you have to add some crabbing, in this
sense slipping and crabbing are additive, i.e. the resulting angle may be
due partly to slip and partly to crab if both are used.

Eric Greenwell wrote:
snip...
After a while, found I preferred a side-slip to a crab;

So do I. Much more fun. but I do it in Cezznas, not my ASW20.

even so, I still use some crab in a strong crosswind.

I think that makes my point. Very sensible with 18 metres of floppy
Schleicher wing to keep dust-free.

GC