How Do U Master A Crosswind Landing?

[737-700 Next Generation Pilot]

Luis wrote:

Crosswind Approach and Landing
Many runways or landing areas are such that landings must be made while the wind is blowing across rather than parallel to the
landing direction; therefore, all pilots should be prepared to cope with these situations when they arise. The same basic principles and
factors involved in a normal approach and landing apply to a crosswind approach and landing. Therefore, only the additional techniques
required for correcting for wind drift are discussed here.

Crosswind landings are a little more difficult to perform than are crosswind takeoffs, mainly due to different problems involved in
maintaining accurate control of the airplane while its speed is decreasing rather than increasing as on takeoff.
There are two usual methods of accomplishing a crosswind approach and landing - the crab method, and the wing low method.
Although the crab method may be easier for the pilot to maintain during final approach, it requires a high degree of judgment and timing
in removing the crab immediately prior to touchdown. The wing low method is recommended in most cases although a combination of
both methods may be used.

Crosswind Final Approach
The crab method is executed by establishing a heading (crab) toward the wind with the wings level so that the airplane's ground track
remains aligned with the centerline of the runway. This crab angle is maintained until just prior to touchdown, when the longitudinal axis
of the airplane must be quickly aligned with the runway to avoid sideward contact of the wheels with the runway. If a long final approach is
being flown, the pilot may use the crab method until just before the roundout is started and then smoothly changing to the wing low
method for the remainder of the landing.

The wing low method will compensate for a crosswind from any angle, but more important, it enables the pilot to simultaneously keep
the airplane's ground track and the longitudinal axis aligned with the runway centerline throughout the final approach, roundout,
touchdown, and after landing roll. This prevents the airplane from touching down in a sideward motion and imposing damaging side
loads on the landing gear.

To use the wing low method, the pilot aligns the airplane's heading with the centerline of the runway, notes the rate and direction of drift,
then promptly applies drift correction by lowering the upwind wing (Fig. 9-11). The amount the wing must be lowered depends on the rate
of drift. When the wing is lowered, the airplane will tend to turn in that direction. It is necessary, then, to simultaneously apply sufficient
opposite rudder pressure to prevent the turn and keep the airplane's longitudinal axis aligned with the runway. In other words, the drift is
controlled with aileron, and the heading with rudder. The airplane will now be side slipping into the wind just enough that both the
resultant flightpath and the ground track are aligned with the runway. If the crosswind diminishes, this crosswind correction must be
reduced accordingly or the airplane will begin slipping away from the desired path.

To correct for very strong crosswind, the slip into the wind must be increased by lowering the upwind wing a considerable amount. As a
consequence, this would result in a greater tendency of the airplane to turn. Since turning is not desired, considerable opposite rudder
must be applied to keep the airplane's longitudinal axis aligned with the runway. In some airplanes, there may not be sufficient rudder
travel available to compensate for the strong turning tendency caused by the steep bank. If the required bank is so steep that full opposite
rudder will not prevent a turn, the wind is too strong to safely land the airplane on that particular runway with those wind conditions. Since
the airplane's capability would be exceeded, it is imperative that the landing be made on a more favorable runway either at that airport or
at an alternate airport.

Flaps can and should be used during most approaches since they tend to have a stabilizing effect on the airplane. However, the degree
to which flaps should be extended will vary with the airplane's handling characteristics, as well as the wind velocity. Full flaps may be
used so long as the crosswind component is not in excess of the airplane's capability or unless the manufacturer recommends
otherwise.

Crosswind Roundout (Flare)
Generally, the roundout can be made as in a normal landing approach but the application of a crosswind correction must be continued
as necessary to prevent drifting (Fig. 9-12).
Since the airspeed decreases as the roundout progresses, the flight controls gradually become less effective; as a result, the crosswind
correction being held would become inadequate. When using the wing low method then, it is necessary to gradually increase the
deflection of the rudder and ailerons to maintain the proper amount of drift correction.

Do not level the wings; keep the upwind wing down throughout the roundout. If the wings are leveled, the airplane will begin drifting and
the touchdown will occur while drifting. Remember, the primary objective is to land the airplane without subjecting it to any side loads
which result from touching down while drifting and to prevent ground looping while the landing is being accomplished.



Crosswind Touchdown
If the crab method of drift correction has been used throughout the final approach and roundout, the crab must be removed the instant
before touchdown by applying rudder to align the airplane's longitudinal axis with its direction of movement. This requires timely and
accurate action. Failure to accomplish this results in severe sideloads being imposed on the landing gear and imparts ground looping
tendencies.

If the wing low method is used, the crosswind correction (aileron into the wind and opposite rudder) should be maintained throughout
the roundout, and the touchdown made on the upwind main wheel (Fig. 9-12).

During gusty or high wind conditions, prompt adjustments must be made in the crosswind correction to assure that the airplane does
not drift as the airplane touches down.

As the forward momentum decreases after initial contact, the weight of the airplane will cause the downwind main wheel to gradually
settle onto the runway.

In those airplanes having nosewheel steering interconnected with the rudder, the nosewheel may not be aligned with the runway as the
wheels touch down because opposite rudder is being held in the crosswind correction. This is the case in airplanes which have no
centering cam built into the nose gear strut to keep the nosewheel straight until the strut is compressed. To prevent swerving in the
direction the nosewheel is offset, the corrective rudder pressure must be promptly relaxed just as the nosewheel touches down.

Crosswind After Landing Roll
Particularly during the after landing roll, special attention must be given to maintaining directional control by use of rudder, or
nosewheel/tailwheel steering, while keeping the upwind wing from rising by use of aileron.
When an airplane is airborne it moves with the air mass in which it is flying regardless of the airplane's heading and speed. However,
when an airplane is on the ground it is unable to move with the air mass (crosswind) because of the resistance created by ground
friction on the wheels.

Characteristically, an airplane has a greater profile or side area, behind the main landing gear than forward of it (Fig. 9-13). With the main
wheels acting as a pivot point and the greater surface area exposed to the crosswind behind that pivot point, the airplane will tend to turn
or "weathervane" into the wind.

Though it is characteristic of most airplanes, this weathervaning tendency is more prevalent in the tailwheel type because the airplane's
surface area behind the main landing gear is greater than in nosewheel type airplanes.




Wind acting on an airplane during crosswind landings is the result of two factors - one is the natural wind which acts in the direction the
air mass is traveling, while the other is induced by the movement of the airplane and acts parallel to the direction of movement.
Consequently, a crosswind has a headwind component acting along the airplane's ground track and a crosswind component acting 90
degrees to its track. The resultant or relative wind, then, is somewhere between the two components. As the airplane's forward speed
decreases during the after landing roll, the headwind component decreases and the relative wind has more of a crosswind component.
The greater the crosswind component the more difficult it is to prevent weathervaning.

The headwind component and the crosswind component can be determined by reference to Figure 9-14. For example:
A relative wind at 20 knots at an angle of 60 degrees to the runway has a headwind component of 10 knots and a 90 degree crosswind
component of 18 knots. Federal Aviation Regulations require that all airplanes, type certificated since 1962, have safe ground handling
characteristics with a 90 degree crosswind component equal to 0.2 Vs0.

Thus, an airplane that stalls at 55 knots in the landing configuration, must have no uncontrollable ground looping (weathervaning)
tendencies with a 90 degree crosswind component of 11 knots (0.2 x 55). It is imperative that pilots determine the maximum crosswind
component of each airplane they fly, and avoid operations in wind conditions that exceed the capability of the airplane.

While the airplane is decelerating during the after landing roll, more and more aileron must be applied to keep the upwind wing from
rising. Since the airplane is slowing down there is less airflow around the ailerons and they become less effective. At the same time the
relative wind is becoming more of a crosswind and exerting a greater lifting force on the upwind wing. Consequently, when the airplane
is coming to a stop the aileron control must be held fully toward the wind.

UMMM THAANX! U Must Be A Pilot LIke Brad Arnt U? Or Or U Are A Flight Instructer? And Brad Im Goin To Tell Your WIFE!!!!!! HA HA. JK

[pegase]

Thanks Luis for this very detailed article. But I don't think I would be able to remember all this during the approach

But there is a small bit of theoric stuff easy to keep in mind which is helpfull:
It is easier to evaluate the effect when the wind is 90° from your route But what about 53°, 23° ??

There are som caracteristic easy to remember values ex:
30*: divide the wind strength by 2 to get the 90° equivalence.
45° 0.707 so in practice "a bit more" than the 2/3
60° 0.86 so in practice a bit more than the 4/5

So if the wind is 20 kts :
If the angle id higher than 70° I take it as a 20 kts 90°

Between 50° and 70° : take it as something beetween 14 kts and 18 kts at 90°

From 30° to 50° ------------- between 10 and 14 kts

from 15° to 30°----------------- between 5 and 10 kts

Below 15°: Don't bother, this is not a crosswind

Or for those flying with a calculator in the hand wind speed * sin (wind direction - route). Don't tell me it is difficult to type on a calculator
while flying an approach... and if so, it is a nice occasion for your wife (or your husband) to contribute to your flight


I never succeeded a full approach with the wing low method. The idea to keep the plane in line with the ground path is nice but then the
plane crabs on the air path making control and stability very difficult.
The usual crab (relative to ground path) method let the plane in line in its air path then the commands can be left neutral with just the yaw
corrections to keep a nice symetric runway shape.
However, if clever enough to do that, applying a bit of wing low just before touch down certainly spare efforts on tires and gears.

BTW: It would be a nice improvement in the FsP report about touch down, to see the wind direction and strength and (if available) the
angle between the plane axis and its ground path to figure out if we have to buy new tires

[SWAFO]

X-Wind landing becoming second nature, so it might be nice to read this article, however the only thing that will perfect your skills is
practice, practice, and more practice!

[Zews]

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Post Edited ( 09-04-10 19:02 )