Power-Off Accuracy Approaches
90° Power-Off Approach
The 90° power-off approach is made from a base leg and requires only a 90° turn onto the final approach. The approach path may be varied by positioning the base leg closer to or farther away from the approach end of the runway according to wind conditions. [Figure 11-31]
The glide from the key position on the base leg through the 90° turn to the final approach is the final part of all accuracy landing maneuvers. Steep approach procedures may be used during the final approach if needed.
The 90° power-off approach usually begins from a rectangular pattern below normal pattern altitude as long as this point is above 500 feet AGL. The before-landing checklist should be completed on the downwind leg.
After a medium-banked turn onto the base leg is completed and key position obtained, the throttle should be completely reduced to idle and the airspeed set to approach speed. [Figure 11-32] At this position, the intended landing spot appears to be on a 45° angle from the aircraft’s nose.
The pilot can determine the strength and direction of the wind from the amount of crab necessary to hold the desired ground track on the base leg. This helps in planning the turn onto the final approach. The base-to-final turn should be planned and accomplished so that upon rolling out of the turn the aircraft is aligned with the runway centerline. Slight adjustments in pitch attitude may be necessary to control the glide angle and airspeed. However, never try to stretch the glide to reach the desired landing spot. After the final approach glide has been established, full attention is given to making a good, safe landing rather than concentrating on the selected landing spot. In any event, it is better to execute a good landing 200 feet from the spot than to make a poor landing precisely on the spot.
180° Power-Off Approach
The 180° power-off approach is executed by gliding with the power off from a given point on a downwind leg to a preselected landing spot. [Figure 11-33]
It is an extension of the principles involved in the 90° power-off approach just described. Its objective is to further develop judgment in estimating distances and glide ratios, in that the aircraft is flown without power from a higher altitude and through a 90° turn to reach the base-leg position at a proper altitude for executing the 90° approach.
The 180° power-off approach requires more planning and judgment than the 90° power-off approach. In the execution of 180° power-off approaches, the aircraft is flown on a downwind heading parallel to the landing runway. The altitude from which this type of approach should be started in the downwind leg is at a normal pattern altitude. This power-off approach should be the normal procedure except for normal light wind landings, the throttle can be brought back to idle between the downwind leg key position and the turn onto the base leg depending on the height and distance from the runway. When abreast of or opposite the desired landing spot or a location closer to the turn onto base if the WSC is further from the runway, the throttle should be closed and the WSC aircraft set to the best glide speed. The point at which the throttle is closed is the downwind key position.
The turn from the downwind leg to the base leg should be a uniform turn with a medium or slightly steeper bank. The degree of bank and amount of this initial turn depends upon the glide angle of the aircraft and the velocity of the wind. Again, the base leg should be positioned as needed for the altitude or wind condition. Position the base leg to conserve or dissipate altitude to reach the desired landing spot. The turn onto the base leg should be made at an altitude high enough and close enough to permit the aircraft to glide to what would normally be the base key position in a 90° power-off approach.
Although the key position is important, it must not be overemphasized or considered as a fixed point on the ground. Many inexperienced pilots have the false understanding of it as a particular landmark, such as a tree, crossroad, or other visual reference to be reached at a certain altitude. This leaves the pilot at a total loss any time such objects are not present. Both altitude and geographical location should be varied as much as practical to eliminate any such conception. After reaching the base key position, the approach and landing are the same as in the 90° power-off approach.
360° Power-Off Approach
The 360° power-off approach is one in which the aircraft glides through a 360° change of direction to the preselected landing spot. The entire pattern is designed to be circular but the turn may be shallowed, steepened, or discontinued at any point to adjust the accuracy of the flightpath. The 360° approach is started from a position over the approach end of the landing runway or slightly to the side of it, with the aircraft headed in the proposed landing direction. [Figure 11-34]
It is usually initiated from approximately 2,000 feet or more above the ground—where the wind may vary significantly from that at lower altitudes. This must be taken into account when maneuvering the aircraft to a point from which a 90° or 180° power-off approach can be completed.
After the throttle is closed over the intended point of landing, the proper glide speed should immediately be established and a medium-banked turn made in the desired direction to arrive at the downwind reference position opposite the intended landing spot. The altitude at the downwind reference position should be approximately 1,000 feet above the ground. After reaching that point, the turn should be continued to arrive at a base-leg key position.
The angle of bank can be varied as needed throughout the pattern to correct for wind conditions and to align the aircraft with the final approach. The turn to final should be completed at a minimum altitude of 300 feet above the terrain. Common errors in the performance of power-off accuracy approaches include:
- Downwind leg too far from the runway/landing area;
- Overextension of downwind leg resulting from tailwind;
- Inadequate compensation for wind drift on base leg;
- Attempting to “stretch” the glide during undershoot;
- Forcing the aircraft onto the runway in order to avoid overshooting the designated landing spot.