Crosswind Landings

CROSS WIND LANDINGS

by Hal Stoen
©1999

first release: 17 January, 1999

revised: 2/19/02

PURPOSE OF THIS TUTORIAL

To show the simulator pilot several techniques that can beused to accomplish landings at an airport when the wind is otherthan 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, Iam attempting to pay back the enjoyment of the years that I hadflying airplanes and hopefully pass on some knowledge that willhelp flight simulator pilots to more enjoy their experiences

ADDITIONS, CORRECTIONS, SUGGESTIONS

I would appreciate any suggestions or corrections you may havethat would make this a better tutorial. Please feel free to emailme with your thoughts or suggestions. Thank you.

INTRODUCTION (a short flying story)

Years ago I was on a flight carrying some customers of thecompany that I worked for to a small airport in the Midwest. Theaircraft was a Cessna 421B that was owned by my company. One ofthe passengers requested to sit in the right front seat duringthe landing, and like most pilots I enjoyed the company in thefront office.

The runway was orientated to the Southeast while the wind wasoffset 45 degrees from the South at about 20 knots with gustsapproaching 30 knots. As we turned final the turbulence began.The aircraft was constantly being buffeted by the turbulant, gustywind. The right wing was well down to prevent drift to the left,and left rudder was in to keep the aircraft from turning to theright. A classic "cross controlled" situation. Due tothe gusty and shifting winds, the aileron and rudder inputs wereconstantly changing. The aircraft touched down on the right maingear first, then I removed just enough of the right aileron inputto allow the left main to touchdown. The rudder was centered brieflyand the nosegear was lowered. With all three wheels in contactwith the runway, right aileron was once again rolled in to keepthe right wing from lifting up.

My guest in the front office turned to me as we were rollingout 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" viewsa cross wind landing- "..something really special..."and hopefully I can impart enough knowledge to you so that youcan perform this type of landing, and "..appreciate it."

SOME BASIC INFORMATION ON WHY ANAIRPLANE FLIES

(If you have read my "Howto fly- Basic" manual, the following is a repeat of thatpart 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 whendoing cross wind landings.)

THE WING In a nutshell(and an over-simplification) an airplane flies because the winghas a curve on the top and is flat on the bottom. As the wingmoves through the air the air that meets the front edge must separateand go up and over or down and under the wing. Because of thecurve on the top of the wing, the air that flows over it has totravel farther than the air below it, The laws of physics saythat the two separated air masses must meet at the trailing edge.The faster moving air on the top in effect creates a lower pressurethan that on the bottom and the wing, along with the airplanethat is attached to it, "rises" upwards. The end resultis called lift.

THE AILERONS Locatedout towards the ends of the wing are the ailerons. These devicesallow the airplane to turn.

Turning the control wheel to the right makes the left ailerongo down and the right aileron to go up. Air striking the downaileron pushes the left wing up and air striking the up aileronpushes the right wing down. The airplane will roll to the rightand continue to roll to the right as long as the wheel is turnedand the ailerons are in this position. For this reason, once thedesired angle of bank is reached the wheel is centered to stopthe roll. The airplane will remain in this bank until you wantto stop the turn. At that time the control wheel is turned inthe opposite direction until the desired angle of bank is reachedand 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 directlyopposite of the ground as it is in level flight. Because of thisthe aircraft will descend in a turn. The steeper the bank, thegreater the descent rate. To counter this, "up elevator"(see below) must be applied in a turn to maintain level flight.

THE ELEVATOR Locatedon the back of the horizontal stabilizer is the elevator. Althoughit is split into a left and a right side it is considered as oneunit.

The elevator moves when you push or pull the control wheel. Pushingthe wheel forward lowers the elevator. Air striking this surfaceforces the tail up and the nose down. Pulling the control wheelback raises the elevator. Air striking this surface forces thetail down and the nose up.

THE RUDDER Thisis located at the rear of the vertical stabilizer. This controlsurface controls the yaw of the aircraft, the nose moving leftor right- or to be exact the movement about the vertical axisof the aircraft.

The rudder is controlled by pedals on the floor. Pushing the rightpedal moves the rudder to the right. Air striking this surfaceforces the tail to the left and the nose to the right. Pushingthe left pedal moves the rudder to the left. Air striking thissurface forces the tail to the right and the nose to the left.

THE FLAPSThis is the last moving surface we have to talk about.Flaps serve three primary purposes on an aircraft, They increaselift, 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 witheither no wind, or having the wind aligned directly with the runway)there is no force trying to push your landing aircraft off ofalignment. Engine thrust is aligned with the runway and the dragof the aircraft is also. The ailerons are hardly used as the pilotadjusts power (engine) and drag (decreased power and flaps) tolower 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 offof runway alignment unless the pilot takes corrective action.Obviously, the greater the angle of the wind in reference to therunway the greater the impact on aircraft drift. If the pilotof the landing aircraft does not take any corrective action theaircraft will either land off of the runway, or will touch downwhile the aircraft has a sideways motion. This sideways motioncan result in loss of control or damage to the landing gear.

COUNTERACTING THE FACTORS IN ACROSS WIND LANDING

Obviously if the pilot were to turn the aircraft into the windthere would be a point where the aircraft would no longer be driftingsideways off of the runway. This would solve the "drift problem",but touching down in this configuration could cause serious damageto the airframe. So, the answer is to turn into the wind enoughto stop drift, but keep the airplane aligned with the runway.

CROSS-CONTROLLED INPUTS

Here's your chance to ignore all of the instruction that youhave had to date about always flying in a coordinated condition.To prevent drifting off of runway alignment, lower (using yourailerons) your wing into the wind. To prevent the aircraft fromturning in that direction use opposite rudder as necessary tokeep the nose of the aircraft aligned with the runway. Note thatunlike when initiating a turn, these control inputs to the aileronsand rudder must be held by you, the pilot. As the airspeed ofthe aircraft slows, these inputs will be decreased as necessaryuntil the aircraft is firmly on the runway.

In our above example, with the wind from the right side, theright wing would be lowered using right aileron. The turning momentwould be counteracted by using left rudder to push the nose backto runway alignment. The result of these inputs is the aircraftapproaching the runway in a wing down, straight ahead fashion.

THE LANDING

Try to use a longer final approach than normal. This allowsyou to adjust your aileron and rudder inputs as necessary to allignyourself with the runway. If the aircraft drifts to the rightdecrease the aileron input and ease off of the left rudder. Dothe opposite if the aircraft drifts to the left- use more rightaileron and more left rudder. If the wind is still making theaircraft drift off of runway alignment use more aileron and oppositerudder as necessary.

Aileron and rudder inputs will constantly change as you nearthe runway. Buildings on the airport will cause eddies of airthat will affect the aircraft and require corrections by the pilot.In addition, in gusty conditions the inputs will increase anddecrease as the wind gusts go up and down. Hey, I never said thiswas going to be easy.

Touchdown speed should be higher than normal. Unlike the greasersyou strive for in normal conditions, in cross wind landings theairplane should be driven right to the ground- not drastically,but firmly. As the right main gear touches down the pilot keepsthe right aileron in as necessary but eases off of the rudderbringing it into a neutral position. Due to nose wheel steering,if the nose of the landing aircraft comes in contact with therunway while the rudder is still pushed over the result couldbe a sudden turning moment on the runway.

Remember that the wind is still acting on the aircraft eventhough you are now on the runway. Maintain the aileron into thewind until the aircraft slows down to taxi speed. It is a goodidea to keep your ailerons turned into the wind as you taxi alongto prevent the wing that is into the wind from lifting up. Pleasesee the taxiing diagram that follows for a visual explanation.

AIRSPEED CONSIDERATIONS

When in cross-controlled (uncoordinated) flight the stall speedof the aircraft increases because you are decreasing lift efficiency.In effect, you are flying sideways and the wing is not gettinga full flow of undisturbed air over it. In addition, the fuselageof the aircraft blocks out a portion of the "downwind wing"further depriving it of lift. Also the pitot tube that drivesthe airspeed indicator is no longer aligned with the air and willread lower than your actual airspeed.

Know that your stall speed will increase when landing in crosswinds and that gusty winds will further aggravate the situation.

In summation:

- Airspeed in a crosswind landing should be higher than ina normal landing. This will allow you to have better control ofthe aircraft as the control surfaces (ailerons and rudder) aremore effective.

- Airspeed will actually be higher than indicated due to thefact that the pitot tube will not be alligned with the flightdirection of the aircraft.

- Airspeed will be moving up and down on the airspeed indicatorin gusty wind conditions, which are more common than not in crosswindlandings.

- The aircraft will have a higher than normal stall speed dueto the "cross-controlled" position of the ailerons andthe 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 CROSSWINDS

Generally speaking use as little flaps as possible. Normallyuse of full landing flaps is good when landing as they slow downthe aircraft and decrease the stall speed. When doing a cross-controlledcrosswind landing, flaps have a tendency to increase the driftingand turning moment of the aircraft. In addition the aircraft isgoing to be landed at a higher than normal speed anyway. Onceon the ground extended flaps allow the wind to have a greaterability to push the aircraft side ways, a consideration in wetor icy runway conditions. Lastly, once on the ground the aircraftshould be braked harder than normal to decrease the time fromthe airplane being an object that wants to fly to becoming anobject moving along on the ground- less flaps means more weighttransfer to the gear and better braking. In any event, retractthe flaps as soon as practical and brake as necessary to get theaircraft into a stable condition on the ground.

ANOTHER METHOD

There is another method. It's called, among other names, "Straightenit out just before touchdown". In this method the pilot rotatesthe landing aircraft into the wind as necessary to prevent drift,but maintains coordinated flight. The aircraft approaches thelanding flare in line with the runway, but pointing towards thecrosswind, what is called a "crabbed condition". Justbefore touchdown the pilot uses aileron and rudder to turn theaircraft back to runway alignment just as the aircraft touchesdown. If this is done too early, or too late, the aircraft landsin a drifting condition and heads off for the boonies.

Obviously this method requires excellent timing, but does haveits advocates.

Doing a successful cross wind landing is one of the rewardingexercises in flying. I hope that the above information is helpfulto you when doing the procedure

TAXIING DIAGRAM

In very windy conditions on the ground the pilot should exerciseextreme caution while taxiing the aircraft. Keep in mind thatan airplane is meant to fly- maneuvering around on the groundis a necessary evil. The lighter the aircraft, obviously the greaterthe chance of the wind having an effect on your airplane whileyou are on the ground. In addition, high wing aircraft are morelikely to be affected than low wing aircraft. Airplanes can bemoved sideways or even tipped over by strong winds while theyare operating on the ground. Use the following diagram to helpavoid the winds' affect on your taxiing aircraft. NOTE: The diagramis based on the use of a tricycle gear aircraft. If a tail draggeris being used, the elevator should be in the "up" positionwith 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 pointingout 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 itshould be, or if you have any suggestions that would makethis a better manual please let me know.

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