Contents
Downwind Landing
The entire downwind approach, even with full flaps, is unexpectedly flat. Flying the familiar pattern results in a go around. The aircraft will be moved by the air mass too tight in the pattern. Trying to adjust the approach and apparent ground speed so that it is "normal" will not work. Further, if we are not in the habit of making full stall landings and even if we are, the landing roundout, flare and roll will require much more runway length than we would ever expect. It is this unexpected distance that often makes the inexperienced pilot try to force the airplane to the ground before it is ready. The resulting flat or hard landing extends the distance required even more. The controls on the ground must be held correctly especially if there is a quartering tailwind during rollout. If you expect to be going into a one-way airport be sure to get some downwind practice first.
The difficulty with downwind landings is the conflict of previous performance and perceived performance. We are used to landing into the wind and the reversal of wind makes things happen differently. Pilot judgment is impaired by the perplexing unfamiliar ground speed being greater than airspeed. By failing to fly an exceptionally extended downwind the full flaps, power off, and minimum approach speed does not get us down. The C-150 requires at least 50% more runway with a 10-kt tail wind added to the normal approach speed. Busy airports frequently will maintain the use of a runway after the winds reverse direction because of traffic or noise considerations. Some airports have a calm-wind runway. This calm wind may exist at ground level but not infrequency the entire approach will be with a tail wind. The IFR straight in ILS with a tail wind may be your only option someday or some night as preferred to circling.. The increased ground speed caused by the tail wind will make for a very flat approach and a long landing roll.
While the inadvertent downwind landing may occur during near calm conditions, it may be required at a one-way airport. This is an airport for which there is only one landing direction regardless of wind. Ruth, the northern most airport on the S. F. sectional is such an airport. This landing as well as cross wind landings, can be practiced at a non-busy tower airports.
ATC is authorized to use any runway when the 'calm wind is less than five knots where it is operationally preferred or requested. ATC will advise of the downwind condition. Pilot requests are usually honored by ATC.
Downwind in a Crosswind
The beginning of a good crosswind landing is determined in how well the pilot maintains the downwind leg a desirable distance from the runway. If the left pattern downwind crab is toward the runway then the right pattern downwind crab must be away from the runway. The key to avoiding any problems in the turn from base to final is dependent upon not letting the downwind track shorten the base leg. The decision should be to keep your downwind legs very wide for all crosswind landings. Skill in maintaining pattern spacing is acquired during ground reference training. A wide base lets you adjust your turn to final if high or low. Suggest you draw it out on a piece of paper.
Base in a Crosswind
Whether a crosswind adds or detracts from your base ground speed and track, it is important that you plan accordingly. The base-to-final turn in a crosswind requires specific procedures to allow you to smoothly align the plane with the runway. If the cross wind is adding to your ground speed, then the turn will have the correct wing low and require opposite rudder to align the nose. If the crosswind is slowing your ground speed, it will be necessary for you to reverse the turn bank immediately on final and apply opposite rudder for alignment. Because the turn to final in each case is so different, it is important to practice both left and right pattern landings in the same flight and wind conditions. Anytime the aircraft is in a cross-control configuration on final, significant forward yoke pressure will be required to maintain the indicated approach speed.
Even when the base to final is properly turned for runway alignment, there is considerable difference in how the turn concludes. Unlike most turns that are completed with the wings level, the crosswind landing turns from base to final are completed with a wing low and opposite rudder to align the nose parallel with the runway. If the base leg has a tailwind adding to your ground speed the turn to final requires only that the opposite rudder he held for nose alignment while the wing continues to be held low into the wind. If the base leg has a headwind the turn to final must be quickly reversed to the opposite bank from entry while the rudder is depressed to keep the nose straight with the runway. The more constant the airspeed the more consistent will be rudder pressures and aircraft performance. Any time the aircraft is in a cross control configuration on final, significant forward yoke pressure will be required to maintain the correct indicated approach speed.
Demonstrated Crosswind Capability
When an aircraft is certified by the FAA, it includes a demonstrated crosswind capability. The capability is based only on the winds available for that time and day. Some capabilities are based on relatively light winds. This means that an average pilot with average competence will be able to land without difficulty. This is a very poor method of determining the flying limits of an airplane.
Students should expect to have trouble with all the variables of airspeed, wind velocity, bank angle and rudder application when learning crosswind landings. Of all standard flight maneuvers the crosswind landing requires the greatest variety of contradictory control applications. Only mastery of the Dutch roll prepares the student for what is going to happen. The Dutch roll removes the intellectual process from the uncoordinated used of controls. If you must think of what to do, you will always be behind the plane.
The crosswind slip to a landing uses the opposite rudder, as applied to keep the aircraft centerline parallel to the runway centerline. The opposing aileron is used to tip the wings so as to slide and maintain the aircraft centered on the runway approach line. The greater the crosswind component the more flaps application is reduced.
Once the crosswind component exceeds that which was used during the certification demonstration the pilot is advised to adjust the use of flaps and speed to suit the conditions. Any time the full application of the controls and increased speed is unable to maintain directional control the go-around is the only option.
Low touchdown speed gives each knot of crosswind additional effect so that additional aileron and rudder deflection--and more bank angle-- is needed to get the slip angle needed to hold runway alignment. Whatever deflection is needed on final approach is only 2/3 of what is needed at flare and touchdown because of slower speed.
A student would be ill advised to self-instruct crosswind landings. Wind gusts can occur that will make the go-around as the only viable option. Without experience a student is apt to be too late with too little.
Dutch Roll
Has been defined as a second order composite stability characteristic that results for the lateral-direction cross-axis coupling of two separate responses to a sideslip. Since there is a coupling between the roll axis and the yaw axis is often considered as a lateral-directional oscillation. Actually the Dutch roll is a relatively easy to control rocking of the wings while holding the nose straight with the rudder. Undesired, the Dutch roll is a nuisance that can occur in turbulence or on an instrument approach. The term is derived from the rocking and rolling motion of 15th century Dutch sailing ships.
What can create a problem is the fact that it is an uncoordinated maneuver. You can create a Dutch roll problem just by trying to fly with only the rudder. While trimmed for level flight, displace the rudder and then put your feet on the floor. The aircraft will waver back and forth and finally return to level flight. Doing the same thing while trimmed at approach speed will aggravate the Dutch roll and make it take longer to smooth out. Do this again but try to use the ailerons only to hold a heading. The adverse yaw of the down-deflected aileron will cause the aircraft to perform Dutch rolls.
Dutch roll introduction:
Students to first plant feet on the floor. Sight a reference point, straight ahead or a heading. Rock the wings back and forth between about 45-deg bank left and right. Hold the nose on the reference point or heading. No rudder. Now try it with rudder. Rock back and forth and back and forth, rhythmically for a minute using the rudder.
A student typically uses on the wrong rudder and wrong pressures in the beginning. It will take a few sessions to get it right. When the Dutch roll finally falls into place you have mastered the basic control skill required for doing crosswind landings.