On Tue, 15 Jul 2008 13:06:54 -0700 (PDT), VectorVictor wrote:
> Crosswinds her I come...
Cool.
Here's the AOPA training article on the subject. I post the full article
because I don't know if you can get in their site without a membership.
Crosswind tutorial
http://flighttraining.aopa.org/ft_magazine/fullstory.cfm?id=5596&issue_title=April
Crab it or slip it, but don't avoid it! Four steps to better crosswind
landings
"I don't want to fly with that guy anymore. He almost ran me off the
runway," confided my good friend Dennis, a highly experienced business-jet
pilot. "Did he land long? I asked, knowing full well that the Challenger
can float halfway down the runway if you carry too much speed on final.
"No, no, no," he said, "he almost ran me off the side of the runway on
account of the crosswind!"
Holy smokes! I thought. Here's a situation where a highly trained, very
experienced jet pilot couldn't muster the basic stick-and-rudder skills to
keep his jet from drifting perilously close the edge of the runway. That's
bad. In fact, that's really bad. If the wheel of a 32,000-pound jet goes
off into the mud at 120 knots, that's a roller coaster ride you may not
walk away from.
The truth is, it really doesn't matter what size airplane you're flying,
crosswind technique is crosswind technique. Pilots who don't learn how to
cope with crosswinds early on never seem to learn to cope with them--that's
why it's so important to learn now. So, with the sincere hope that you
never go off into the mud, here are four steps to help make your crosswind
landings easier and safer.
1. Get lined up early
You may have heard the old aviation adage "A great landing starts 10 miles
out." What that really means is that a great landing usually follows a
great approach. While a Chuck Yeager might produce a great landing from an
unstable, rickety approach, the rest of us use the stabilized approach
concept to give us a fighting chance.
A stabilized approach is nothing new; airline and business aviation pilots
have been using it for years. It's so important they've incorporated it
into their training programs and standard operating procedures. Basically,
a stabilized approach is an approach where the airplane is lined up for the
runway, on target airspeed, on glide path (electronic or visual), and fully
configured for landing (flaps and gear down, propeller at high rpm). The
airplane should be stabilized at an altitude no less than 500 feet above
airport elevation.
It's best to line up early on the extended runway centerline. Here, the
difference between heading and track becomes crucial. Heading, of course,
it the actual heading of the airplane, or simply where the nose is pointed.
Track, on the other hand, is the course it follows over the ground--the
actual flight path referenced to the surface. In a no-wind condition,
heading and track are the same. But throw a little crosswind into the mix,
and you can see that the airplane will drift downwind as it flies.
To compensate for this drift, you're going to have to point the nose of the
airplane into the wind slightly to set up a crab angle or wind correction
angle to maintain a straight track. The amount of crab angle depends on the
strength of the wind. And don't make the rookie mistake of trying to line
up by putting the runway directly out in front of the windshield. If
there's a good crosswind, and you're holding a crab, the runway may not be
in front at all; it could easily be at your 11 or 1 o'clock position. The
nice thing about flying with a wings-level crab angle (as opposed to a side
slip with opposite rudder) is that it's much more comfortable for your
passengers.
How do you know if you're on the extended runway centerline? That's another
troublesome issue for students. One easy way to tell is to compare the far
end of the runway to the near end. If the ends are positioned vertically,
with the far end centered above the near end, then the airplane is on the
extended centerline. However, if the far end is to the right of the near
end, the airplane's to the right of the centerline. Conversely, if the far
end is to the left, the airplane's to the left.
Another thing to keep in mind is that usually, you'll need less crab as you
descend toward the runway, because the wind speed is being reduced by
surface friction. However, if you're flying over a flat surface, like
desert or water, the wind speed may not decrease as you descend. In that
case, you may have to land with the full force of the crosswind at the
surface. Moreover, surface inversions can cause a noticeable change in wind
speed and direction during approach.
2. Use partial flaps
This is one of the best-kept secrets of crosswind landings, and
surprisingly, many pilots don't even consider it! Since most general
aviation airplanes have landing distances of fewer than 2,000 feet, runway
length is rarely a factor even with partial-flap landings. For example, the
pilot's operating handbook (POH) for the Cessna 172P states that for a
flaps up landing you should allow for a 35-percent increase in landing
distance. That's insignificant if you're landing on a 5,000-foot-long
runway.
In a crosswind or gusty situation, however, full-flap landings can be more
trouble than they're worth. This is because fully extended flaps present a
larger surface area for that crosswind to affect, blowing you around. Flaps
catch the wind just like a kite. Now while it's true that flaps lower your
stall speed, allowing for a slower approach speed, you may not necessarily
want that. Besides, that benefit usually comes at some intermediate flap
setting before full extension; any further flap extension generally just
adds drag. But don't just take my word for it, read what the manufacturer
has to say in the POH. Here's an excerpt from the Normal Procedures section
of a popular four-seat general aviation airplane: "Normal landing
approaches can be made with power-on or power-off with any flap setting
desired. Surface winds and air turbulence are usually the primary factors
in determining the most comfortable approach speeds." (Italics added)
Plus, with partial flaps, your approach speed will have to be little
faster. In the example above, along with the 35-percent increase in landing
distance, the POH also recommends adding 7 knots to the approach speed for
a no-flaps landing. In fact, assuming runway length is not a factor, adding
extra airspeed is not a bad idea for any landing with crosswinds or
gusts--with or without flaps. That's because a faster approach speed means
better airplane control, especially lateral (or roll) control. In other
words, with more airspeed, your ailerons will be more responsive--exactly
what you want if gusty crosswinds are blowing you around. Just don't get
carried away; coming in 15 or 20 knots faster than the recommended approach
speed can cause problems. You will eat up more runway during the landing
flare, and are subjected to crosswind effects for a longer period of time
as you float--and float--down the runway.
3. Touch down on one wheel only
This seems like a no-brainer, but surprisingly many pilots just can't drive
themselves to do it. Landing on both main wheels is fine when the wind's
straight down the runway, but it's not desirable or safe when there's a
crosswind. That's because you'll be touching down while the airplane's
moving sideways or drifting downwind. Touching down while in a drift can
cause damaging side loads on the tires, wheels, and landing gear--not to
mention you and the airplane, if it results in a loss of control.
The only way to touch down without sideward drift is to land on the upwind
wheel. The slight bank generates a slight horizontal component of lift,
which cancels the crosswind component. Of course, the airplane seeks to
turn when you bank it, so you'll have to hold some opposite rudder to keep
the fuselage lined up with the runway. In other words, control drift with
ailerons, control heading with rudder.
Thus, one of the marks of a great crosswind landing is a touchdown with
little or no sideward drift. You're trying to touch down in a wing-low
sideslip, on the upwind wheel, with zero drift, and with the longitudinal
axis of the airplane (from the tip of the spinner to the tail) parallel to
the runway. Accordingly, this crosswind landing technique is called the
sideslip or wing-low method.
Therefore, at some point before touchdown, you'll have to transition the
airplane from a crab to a wing-low sideslip. Depending on conditions, you
could choose to do this at about 500 feet above the runway, or you could
delay the transition until the airplane is closer to ground. It's all a
judgment call that depends on the conditions at hand, your skills, and your
comfort level.
When you do decide to transition, you'll do so by lowering the upwind wing
slightly, while simultaneously adding opposite rudder pressure to keep the
airplane's nose from turning. The resulting bank should be adjusted to keep
the airplane from drifting, and the rudder pressure adjusted to keep the
fuselage aligned with the runway. If the crosswind component lessens
because of surface friction as you descend on your approach, you'll have to
reduce the amount of bank and rudder pressure as required; flare and
touchdown should be made while holding these corrections. Because the
upwind wing is banked slightly, touchdown should occur on the upwind main
first, followed by the downwind main, and finally the nosewheel.
4. Keep flying until you're stopped
Vigilance is the key here. A large number of pilots quit flying the
airplane once it touches down. But this is precisely when you should be on
the alert! Pilots let down their guard, become distracted, and end up
losing control of the airplane to a wind gust. Never stop flying the
airplane until it is shut down and chocked.
Consequently, you should hold those aileron and rudder crosswind
corrections until the airplane has slowed to taxi speed. As the airplane
slows down, the ailerons and rudder become less effective, so you'll have
to add more control deflection. Finally, whenever crosswinds are involved,
there are two figures in the POH you should be familiar with. The first one
is the wind component chart. Given the wind speed and the angle between the
wind direction and the runway, this chart shows you the headwind (or
tailwind) and crosswind components. The use of this chart or its equivalent
is a must whenever there's any doubt about how much crosswind exists for a
particular approach and landing. Sadly, there have been more than a few
high-profile airline and corporate jet accidents caused by a crew's
miscalculations of tailwind or crosswind components where the use of this
simple chart could have saved the day.
The other chart you should be familiar with is the taxiing diagram. This
diagram shows the proper control positions to hold to maintain directional
control and balance while taxiing in strong winds. This procedure should be
memorized.
This is probably the most important tip of all: Learn to tackle crosswinds
early in your flight training. Sure, crosswinds present some unique
challenges, but they also allow you to savor the satisfaction of a properly
executed "one wheel" crosswind landing. So, the next time the winds are
blowing across the runway at your local airport, grab your instructor and
under his or her tutelage go out and practice your crosswind landings until
you've got them nailed. Whether you're an aspiring professional pilot or a
recreational flier, you'll be making crosswind landings for the rest of
your aviation career.
Christopher L. Parker is a CFI and an aviation author, speaker, and FAA
remedial training specialist. He flies internationally as a contract
captain on a Bombardier Challenger business jet and lives in Los Angeles.
Dallas
Bill
VectorVictor
