On Tue, 16 Oct 2007 23:41:18 -0400, Dudley Henriques
wrote:

Kyle Boatright wrote:
I'm always puzzled by the impact obstacles (trees, buildings, etc) have on a
crosswind.

On the day ten years ago when I earned my tailwheel endorsement, there was a
15 knot direct crosswind above the treeline. But, the field was buried in a
small gap between 75' trees and the crosswind effectively disappeared once
the airplane descended below the trees. Even better, there was no
turbulence. I'm still surprised at how easy it was to land in those
conditions.

As opposed to yesterday, when I was landing at a nearby field in a 10 knot,
60 degree crosswind. There was a row of 50' trees a hundred and fifty feet
upwind of the runway, and those trees (presumably) created a nasty burble at
groundlevel.

Because of my widely varied experience with obstacles interacting with
crosswinds, I struggle to pick the *best* runway or landing spot. Is it
better to bet on an obstacle reducing the crosswind, or is that obstacle
likely to cause a burble that will result in a rotten (or exciting) landing?
I'm still trying to crack the code on this one...

Thoughts?

KB




Hi KB;

The way I've always handled this and taught others to handle it is NEVER
to fly ANY approach based entirely on expected wind conditions. I know
this sounds over simplistic on the face of it, but you'd be surprised
how many pilots get a handle on wind somewhere between the base turn and
final and get mentally nailed into that wind mindset. The result can

This as well may sound over simplistic and I hope I put it into the
proper words and context.

Although I take notice of the winds, both reported and forecast, I
treat each landing pretty much the same be it on a calm day or with
gusty wind. Remember, calm hot summer days may be loaded with up and
down drafts that are present when wind conditions are reported as
calm. IOW the only preconceived notions I have going into a landing
are the winds are likely to be something other than forecast.

Winds and gusts may show up on an otherwise calm day. Winds may be
higher or less than forecast and the directions may be different or
variable. Conversely a strong cross wind on final may turn out to be a
direct head wind in ground effect or it might even have turned calm.

I fly the plane and adjust to the conditions of the moment. The plane
and I react and correct for changes. I don't have to stop and think
"Hmmm the winds just changed 90 degrees, to correct for that I need to
add left aileron and a bit of right rudder to stay aligned with the
runway. Unless the winds are light, the pilot does not have time to
reason all of this out. Like riding a bicycle, the movements to
correct for drift one way or the other should be ingrained and
instinctive as should adding or retarding throttle with up and down
drafts. Any pilot who pays attention and practices a bit should be
able to do this by the time they take the check ride. Certainly they
will have to make adjustments when they move on to different types of
aircraft where speed, inertial, control harmony and response must be
taken into consideration. You've reduced the thinking and responding
time to one of response/reaction times.

easily be over concentration on an expected wind direction down through
the approach. Then a sudden gust or wind change catches you napping. The
result of that is a second or two DELAY in reaction time to the change.
Usually it comes out ok, but if a pilot gets caught at exactly the wrong
instant (usually down low just before the flare or entering the flare)
that two second delay can suddenly become a potentially serious affair.

When I was getting to the point where I could handle cross winds
pretty well my instructors took me up to Houghton Lake (HTL). I think
most pilots have a place like HTL some where nearby. The paved runway
is a 4000' 09/27. About 200 yards to the north is a very straight and
tall tree line with the ground level probably 20 or so feet above the
runway although it's not apparent. When the wind is out of the north
it drops over the trees to form a relatively smooth flow over the
runway from the North. to the South of the runway is a slight rise.
For some reason the winds seem to form an "S" over the runway. IOW as
you are descending on final for 27 you have a strong, right cross
wind, but some where around a 100 feet you hit a bit of turbulence and
are likely to find the wind has switched 180 degrees and is out of the
South. Around 30 feet or so there is another layer of turbulence and
you are back to a wind out of the North. OTOH you can't expect it to
be this way every time the wind is out of the North.

I've been 90 degreed up there a couple of times and it's usually right
over the threshold. Pay attention and it's nothing more than a
reminder. It's not a place to be complacent with a mind set that is
all set for a wind out of the North. That could be expensive, painful,
or both.


What I like to instill in the pilots I train (in my case have trained
:-) is what I call a non committal mindset for wind on the approach.
Loosely explained, this simply amounts to a pilot developing a habit
pattern that digests wind data as received, and begins the approach with
that data in mind, but instead of thinking of wind direction, I like
pilots to think wind CONTROL.
By thinking aircraft control as opposed to expected wind, what happens
is that you are mentally and physically a bit more "loose" on the
approach because you're not expecting a specific wind correction; you
are correcting for what's HAPPENING NOW all through the approach.
Basically it's nothing more than a slight change in the way a pilot
THINKS and FLIES the approach. You're cutting into that 2 second
reaction time because now you're flying the approach as though the winds
were unexpected instead of expected. You have nothing to lose and
everything to gain by using this mindset. If the winds are as expected,
you're automatically correcting for them. But if you get nailed, you're
loose and expecting that as well!!
DH
Some years back I was standing along side of 18/36 at 3BS when a
company pilot delivered a brand new A36 to one of our more
impoverished. The winds were strong and gusty out of the West. 24
would have been a more logical choice, but the FBO was about 1300 feet
down 36 and that's where he was headed.

As we stood there in the wind I watched that A36 come in with those
big flaps pointed down. I could say the wings appeared to be
absolutely steady without exaggeration. OTOH you could see the
ailerons making some rather large excursions. That guy was good! He
was the epitome of a pilot who reacts to the moment with just the
right amount of input. No way can you fly like that and take time to
think about what happening and what you need to do for control inputs.


Roger (K8RI)