CROSS WIND LANDINGS
by Hal Stoen
first release: 17 January, 2010
revised: 2/02/02, 2/22/2011
PURPOSE OF THIS TUTORIAL
To show the simulator pilot several techniques that can be used to accomplish landings at an airport when the wind is other than directly aligned with the runway.
The suggestions in this tutorial are based on personal experience- I certainly don't pretend to be a guru of aviation knowledge. In writing this tutorial, and other works that I have done, I am attempting to pay back the enjoyment of the years that I had flying airplanes and hopefully pass on some knowledge that will help flight simulator pilots to more enjoy their experiences
ADDITIONS, CORRECTIONS, SUGGESTIONS
I would appreciate any suggestions or corrections you may have
that would make this a better tutorial. Please feel free to email
me with your thoughts or suggestions. Thank you.
INTRODUCTION (a short flying story)
Years ago I was on a flight carrying some customers of the company that I worked for to a small airport in the Midwest. The aircraft was a Cessna 421B that was owned by my company. One of the passengers requested to sit in the right front seat during the landing, and like most pilots I enjoyed the company in the front office.
The runway was orientated to the Southeast while the wind was offset 45 degrees from the South at about 20 knots with gusts approaching 30 knots. As we turned final the turbulence began. The aircraft was constantly being buffeted by the turbulent, gusty wind. The right wing was well down to prevent drift to the left, and left rudder was in to keep the aircraft from turning to the right. A classic "cross controlled" situation. Due to the gusty and shifting winds, the aileron and rudder inputs were constantly changing. The aircraft touched down on the right main gear first, then I removed just enough of the right aileron input to allow the left main to touchdown. The rudder was centered briefly and the nosegear was lowered. With all three wheels in contact with the runway, right aileron was once again rolled in to keep the right wing from lifting up.
My guest in the front office turned to me as we were rolling out and said "I think I just witnessed something really special, but I don't have the knowledge to appreciate it."
That pretty well sums up how an "outsider" views
a cross wind landing- "..something really special..."
and hopefully I can impart enough knowledge to you so that you
can perform this type of landing, and "..appreciate it."
SOME BASIC INFORMATION ON WHY AN AIRPLANE FLIES
(If you have read my "How to fly computer flight simulators "manual", the following is a repeat of that part of the manual and you may wish to skip over it. However, the reader should be aware that proper knowledge of basic aerodynamics, while important in a normal landing is even more important when doing cross wind landings.)
THE WING In a nutshell
(and an over-simplification) an airplane flies because the wing
has a curve on the top and is flat on the bottom. As the wing
moves through the air the air that meets the front edge must separate
and go up and over or down and under the wing. Because of the
curve on the top of the wing, the air that flows over it has to
travel farther than the air below it, The laws of physics say
that the two separated air masses must meet at the trailing edge.
The faster moving air on the top in effect creates a lower pressure
than that on the bottom and the wing, along with the airplane
that is attached to it, "rises" upwards. The end result
is called lift.
THE AILERONS Located
out towards the ends of the wing are the ailerons. These devices
allow the airplane to turn.
Turning the control wheel to the right makes the left aileron go down and the right aileron to go up. Air striking the down aileron pushes the left wing up and air striking the up aileron pushes the right wing down. The airplane will roll to the right and continue to roll to the right as long as the wheel is turned and the ailerons are in this position. For this reason, once the desired angle of bank is reached the wheel is centered to stop the roll. The airplane will remain in this bank until you want to stop the turn. At that time the control wheel is turned in the opposite direction until the desired angle of bank is reached and then centered. Once the airplane is level you stop the turn. Turning left is of course, the opposite procedure.
Notice that in a turn (bank) the lift is no longer directly opposite of the ground as it is in level flight. Because of this the aircraft will descend in a turn. The steeper the bank, the greater the descent rate. To counter this, "up elevator" (see below) must be applied in a turn to maintain level flight.
THE ELEVATOR Located
on the back of the horizontal stabilizer is the elevator. Although
it is split into a left and a right side it is considered as one
The elevator moves when you push or pull the control wheel. Pushing the wheel forward lowers the elevator. Air striking this surface forces the tail up and the nose down. Pulling the control wheel back raises the elevator. Air striking this surface forces the tail down and the nose up.
THE RUDDER This
is located at the rear of the vertical stabilizer. This control
surface controls the yaw of the aircraft, the nose moving left
or right- or to be exact the movement about the vertical axis
of the aircraft.
The rudder is controlled by pedals on the floor. Pushing the right pedal moves the rudder to the right. Air striking this surface forces the tail to the left and the nose to the right. Pushing the left pedal moves the rudder to the left. Air striking this surface forces the tail to the right and the nose to the left.
This is the last moving surface we have to talk about.
Flaps serve three primary purposes on an aircraft, They increase
lift, lower the stalling speed and they act as air brakes.
FACTORS AT PLAY IN A NORMAL LANDING
In a normal landing (defined here as landing on a runway with
either no wind, or having the wind aligned directly with the runway)
there is no force trying to push your landing aircraft off of
alignment. Engine thrust is aligned with the runway and the drag
of the aircraft is also. The ailerons are hardly used as the pilot
adjusts power (engine) and drag (decreased power and flaps) to
lower the landing aircraft on to the runway.
FACTORS AT PLAY IN A CROSS WIND LANDING
In a cross wind landing the wind will push the aircraft off
of runway alignment unless the pilot takes corrective action.
Obviously, the greater the angle of the wind in reference to the
runway the greater the impact on aircraft drift. If the pilot
of the landing aircraft does not take any corrective action the
aircraft will either land off of the runway, or will touch down
while the aircraft has a sideways motion. This sideways motion
can result in loss of control or damage to the landing gear.
COUNTERACTING THE FACTORS IN A CROSS WIND LANDING
Obviously if the pilot were to turn the aircraft into the wind there would be a point where the aircraft would no longer be drifting sideways off of the runway. This would solve the "drift problem", but touching down in this configuration could cause serious damage to the airframe. So, the answer is to turn into the wind enough to stop drift, but keep the airplane aligned with the runway.
Here's your chance to ignore all of the instruction that you have had to date about always flying in a coordinated condition. To prevent drifting off of runway alignment, lower (using your ailerons) your wing into the wind. To prevent the aircraft from turning in that direction use opposite rudder as necessary to keep the nose of the aircraft aligned with the runway. Note that unlike when initiating a turn, these control inputs to the ailerons and rudder must be held by you, the pilot. As the airspeed of the aircraft slows, these inputs will be increased as necessary (slower speed, lower air impact with the control surfaces, less effect) until the aircraft is firmly on the runway.
In our above example, with the wind from the right side, the right wing would be lowered using right aileron. The turning moment would be counteracted by using left rudder to push the nose back to runway alignment. The result of these inputs is the aircraft approaching the runway in a wing down, straight ahead fashion.
Try to use a longer final approach than normal. This allows you to adjust your aileron and rudder inputs as necessary to allign yourself with the runway. If the aircraft drifts to the right decrease the aileron input and ease off of the left rudder. Do the opposite if the aircraft drifts to the left- use more right aileron and more left rudder. If the wind is still making the aircraft drift off of runway alignment use more aileron and opposite rudder as necessary.
Aileron and rudder inputs will constantly change as you near the runway. Buildings on the airport will cause eddies of air that will affect the aircraft and require corrections by the pilot. In addition, in gusty conditions the inputs will increase and decrease as the wind gusts go up and down. Hey, I never said this was going to be easy.
Touchdown speed should be higher than normal. Unlike the greasers you strive for in normal conditions, in cross wind landings the airplane should be driven right to the ground- not drastically, but firmly. As the right main gear touches down the pilot keeps the right aileron in as necessary but eases off of the rudder bringing it into a neutral position. Due to nose wheel steering, if the nose of the landing aircraft comes in contact with the runway while the rudder is still pushed over the result could be a sudden turning moment on the runway.
Remember that the wind is still acting on the aircraft even though you are now on the runway. Maintain the aileron into the wind until the aircraft slows down to taxi speed. It is a good idea to keep your ailerons turned into the wind as you taxi along to prevent the wing that is into the wind from lifting up. Please see the taxiing diagram that follows for a visual explanation.
When in cross-controlled (uncoordinated) flight the stall speed of the aircraft increases because you are decreasing lift efficiency. In effect, you are flying sideways and the wing is not getting a full flow of undisturbed air over it. In addition, the fuselage of the aircraft blocks out a portion of the "downwind wing" further depriving it of lift. Also the pitot tube that drives the airspeed indicator is no longer aligned with the air and will read lower than your actual airspeed.
Know that your stall speed will increase when landing in cross winds and that gusty winds will further aggravate the situation.
- Airspeed in a crosswind landing should be higher than in a normal landing. This will allow you to have better control of the aircraft as the control surfaces (ailerons and rudder) are more effective.
- Airspeed will actually be higher than indicated due to the fact that the pitot tube will not be aligned with the flight direction of the aircraft.
- Airspeed will be moving up and down on the airspeed indicator in gusty wind conditions, which are more common than not in crosswind landings.
- The rudder must be centered, or nearly so, when the nose gear touches down. Due to the inter-connect between the nose gear and the rudder used for ground steering you do not want the front of the airplane pointing in any direction other than down the runway. The crosswind landing is exciting enough in itself.
- The aircraft will have a higher than normal stall speed due to the "cross-controlled" position of the ailerons and the rudder.
- You will use more runway than in a "normal" landing.
This is due primarily to a higher touchdown speed.
USING FLAPS WHILE LANDING IN CROSS WINDS
Generally speaking use as little flaps as possible. Normally use of full landing flaps is good when landing as they slow down the aircraft and decrease the stall speed. When doing a cross-controlled crosswind landing, flaps have a tendency to increase the drifting and turning moment of the aircraft. In addition the aircraft is going to be landed at a higher than normal speed anyway. Once on the ground extended flaps allow the wind to have a greater ability to push the aircraft side ways, a consideration in wet or icy runway conditions. Lastly, once on the ground the aircraft should be braked harder than normal to decrease the time from the airplane being an object that wants to fly to becoming an object moving along on the ground- less flaps means more weight transfer to the gear and better braking. In any event, retract the flaps as soon as practical and brake as necessary to get the aircraft into a stable condition on the ground.
There is another method. It's called, among other names, "Straighten it out just before touchdown". In this method the pilot rotates the landing aircraft into the wind as necessary to prevent drift, but maintains coordinated flight. The aircraft approaches the landing flare in line with the runway, but pointing towards the crosswind, what is called a "crabbed condition". Just before touchdown the pilot uses aileron and rudder to turn the aircraft back to runway alignment just as the aircraft touches down. If this is done too early, or too late, the aircraft lands in a drifting condition and heads off for the boonies.
Obviously this method requires excellent timing, but does have its advocates.
Doing a successful cross wind landing is one of the rewarding exercises in flying. I hope that the above information is helpful to you when doing the procedure
In very windy conditions on the ground the pilot should exercise extreme caution while taxiing the aircraft. Keep in mind that an airplane is meant to fly- maneuvering around on the ground is a necessary evil. The lighter the aircraft, obviously the greater the chance of the wind having an effect on your airplane while you are on the ground. In addition, high wing aircraft are more likely to be affected than low wing aircraft. Airplanes can be moved sideways or even tipped over by strong winds while they are operating on the ground. Use the following diagram to help avoid the winds' affect on your taxiing aircraft. NOTE: The diagram is based on the use of a tricycle gear aircraft. If a tail dragger is being used, the elevator should be in the "up" position with a wind from in front of the aircraft.
On 2/18/2002, reader Andy Lindstrom suggested this memory cue: "Steer into a headwind, and dive away from a tailwind." Thank you Andy.
Note: diagram corrected 3/30/01. Appreciation to Maurice Kay for pointing out an error.
A REQUEST FROM "YOUR INSTRUCTOR" If there is anything that is presented in a confusing manner, or if something was not treated with the attention you feel it should be, or if you have any suggestions that would make this a better manual please let me know.
This narrative, along with aditional content, is available as a CD or an eBook.
For CD information click here. For eBook information click here.
revised: 3/2/2010: Corrected control input terminology in the "Cross-Controlled-Input" section. Thank you to Sam Burke for pointing this out.
revised 2/22/2011: Ted Seastrom pointed out that more emphasis should be given to centering the nose wheel before lowering the nose gear. I agreed.
16 January, 1999
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