Power-on Approach and Landing for Turbulant Air
Power-on approaches at an airspeed above the normal approach speed should be used for landing in turbulent air. This provides for more energy and positive control of the aircraft when strong horizontal wind gusts, wind sheer, or up and down drafts, are experienced. Like other power-on approaches (when the pilot can vary the amount of power), a coordinated combination of both speed and power adjustments is usually required. It is easiest to think of flying the aircraft onto the ground at an airspeed above the stall speed. The additional power provides the pilot the ability to reduce the descent rate to touch the wheels gently to the surface at a higher speed. Landing in turbulent air is where practice and experience in energy management are utilized. This precise coordination of power and speed for higher energy landings should first be practiced in calm air and can be used as the next step in learning landings after the student becomes proficient at low approaches.
To determine the additional approach speed to flying in turbulence, one procedure is to use the normal approach speed plus one-half of the wind gust factors. The wind gust factor is determined by how much the airspeed varies while flying. If the normal approach speed is 50 knots and the wind gusts are at 15 knots, an airspeed of 57 knots is appropriate. Another method is to ensure the aircraft is at least at VY speed plus the wind gust factor. In any case, the airspeed that the aircraft manufacturer recommends.
An adequate amount of power should be used to maintain the proper airspeed and descent path throughout the approach and the throttle retarded to idling position only after the main wheels contact the landing surface. Care must be exercised in not closing the throttle before the pilot is ready for touchdown. In this situation, the sudden or premature closing of the throttle may cause a sudden increase in the descent rate that could result in a hard landing.
Landings from power-on approaches in turbulence should be such that the touchdown is made with the aircraft in approximately level flight attitude. The pitch attitude at touchdown should be only enough to prevent the nosewheel from contacting the surface before the main wheels have touched the surface. Most WSC are designed so the front wheel is higher than the back wheels in this situation, but each WSC is different. This must be evaluated for each model. After touchdown, the pilot should reduce the throttle to idle and pull the control bar all the way to the chest to lower the nose and prevent the WSC aircraft from lifting off until it slows below the stall speed. The aircraft should be allowed to decelerate normally with the aerodynamic braking of the wing with the nose lowered, and assisted by the wheel brakes as required.
Crosswind Approaches and Landings
Many runways or landing areas are made such that landings must be made while the wind is blowing across rather than parallel to the landing direction. All pilots should be prepared to cope with these situations when they arise. The same basic principles and factors involved in a normal and power-on approach and landing apply to a crosswind approach and landing; therefore, only the additional procedures required for correcting for wind drift are discussed here.
Crosswind approaches and landings are more challenging than normal landings because of the wind drift in the pattern, crab angles on approach, and generally more mechanical turbulence for the final approach and roundout because of buildings and/or trees along the sides of the runway. Since mechanical turbulence would typically increase as the aircraft descends closer to the ground, power-on approaches and techniques for flying in turbulence should be utilized.
Crosswind Pattern Procedures
Since WSC aircraft typically fl y tighter patterns, the pattern should be modified if the crosswind is in a direction pushing the WSC aircraft toward the runway. Refer to Figure 11-24 for the following discussion.
The normal or typical pattern downwind and base for calm winds is shown in blue. This pattern would also be used if there were an opposite crosswind from that shown blowing from the runway toward the base leg. If a strong crosswind (15 knots as an example, which is a limitation for many WSC) is noticed while flying the down wind or the runway wind indicators show this crosswind, at “A” the decision should be made to modify the pattern, making it wider by flying out to location “B.” An extended downwind should then be made farther than the typical normal pattern to “C.” This provides additional distance from the runway for the base leg, which will be at a much higher groundspeed than normal because the WSC is flying in a strong tailwind from point “C” to “D.” The turn must be made at “D” to set up for final approach at “E” where there is a significant crab angle. From the final approach at “E” to touchdown, the pilot has sufficient time to establish the ground track in the center of the runway and evaluate if the landing should be completed, a go-around performed, or a different landing location selected with more favorable wind conditions.
Effects and Hazards of High Crosswinds for Approaches and Landings
Figure 11-24 illustrates a scenario that includes the effects and hazards of high wind, referencing groundspeed, high rates of turn, and power requirements for making downwind turns in close proximity to the ground.
During the downwind leg of the pattern, the pilot does not notice the strong wind blowing the WSC aircraft into the runway. From points A to W, the pilot reduces power as normal but does not crab into the wind and drifts with the wind toward the runway between points A and W. This leads the pilot to be closer to the runway when he or she turns onto base. The pilot turns onto base and is traveling at high groundspeed and the strong tailwind leads to the pilot passing the runway centerline normal final approach at point X. From points X to Y, the pilot starts the turn for final approach late because of the high groundspeed. The WSC aircraft past the runway centerline leads the pilot to increase the bank to make it back to the centerline. The previous errors lead the pilot into a high bank angle at low altitude pointed down in a rapid descent. This leads the pilot to apply full power at Y, which drives the WSC aircraft into ground at point Z.
The error chain that led to this accident could have been avoided at two primary points. First, the pilot should have noticed flying in a crosswind or indications of a strong crosswind on the runway from airport wind indicators at A. He or she should have then widened the pattern into the crosswind from A to B and performed the recommended crosswind procedure described earlier.
Second, if the pilot did not realize the high wind blowing to the runway until point X was reached, the wings should have been leveled and a go-around performed without trying to “make it” back to the runway as shown in the yellow “go-around” path shown on Figure 11-24.
For strong crosswinds beyond the capabilities of the pilot or limitations of the WSC aircraft, an alternate landing strip should be found. This could be another airport or landing strip that faces into the wind. An option at uncontrolled airports is to choose an alternate runway or even a taxiway that faces into the wind. Some of the larger airports with wide runways make it possible to land at an angle if needed; some are wide enough to land across the main runway. At towered airports, the air traffic controller can assist the pilot and provide an alternate landing area if requested.
When in final approach, the wind correction angle (crab angle) is established by heading toward the wind with the wings level so that the aircraft’s ground track remains aligned with the centerline of the runway. [Figure 11-25]
This crab angle is maintained all the way to touchdown, when the rear wheels hit first and rotate the carriage and wing around so the front wheel touches the ground with the carriage going straight. However, if in turbulent air or pitched forward during the touchdown, with the front wheel touching the ground first, the pilot should lightly control the steering of the front wheel to be headed in the direction the carriage is going. WSC carriage front landing gear typically has camber that tends to steer the front wheel naturally in the direction of travel, so a light touch on the front wheel as it touches the ground allows it to find its own direction of travel. Once the front wheel is on the ground, lower the nose to keep the WSC on the ground and steer as required down the center of the runway.
The procedure for the wing during the roundout is the same as that for normal and turbulent roundout and touchdowns. The exception is that after touchdown the windward wing should be lowered slightly so the wind cannot get under it to flip the WSC aircraft during later landing roll and taxi.
Maximum Crosswind Velocities
Takeoffs and landings in certain crosswind conditions are inadvisable and even dangerous. [Figure 11-26]
If the crosswind is great enough, a hazardous landing condition may result. Therefore, takeoff and landing capabilities with respect to the reported surface wind conditions and available landing directions must be considered.
WSC crosswind limitations have been tested and are included in the POH. The headwind and crosswind components for a given situation can be determined by reference to a crosswind component chart. [Figure 11-27]
It is imperative that pilots determine the maximum crosswind component of each aircraft flown and avoid operations in wind conditions that exceed the capability of the aircraft. The automatic weather observation system (AWOS) or automatic surface observation system (ASOS) at airports is useful in determining the measured velocity for this evaluation.
Common errors in the performance of crosswind approaches and landings include:
- Failure to recognize a strong crosswind blowing at the runway during the downwind leg;
- Failure to modify the pattern for strong crosswind conditions;
- Failure to do a go-around when the final approach to the runway is downwind of the runway centerline;
- Attempting to land in crosswinds that exceed the pilot’s capabilities;
- Attempting to land in crosswinds that exceed the aircraft’s maximum demonstrated crosswind component;
- Inadequate compensation for wind drift on the turn from base leg to final approach, resulting in undershooting or overshooting;
- Inadequate compensation for wind drift on final approach;
- Unstabilized approach;
- Touchdown while drifting;
- Excessive pressure on the nosewheel steering during touchdown;
- Excessive airspeed on touchdown;
- Failure to apply appropriate flight control inputs during rollout;
- Failure to maintain direction control on rollout; and
- Excessive braking.