Downwind Leg

Looking ahead to a good, stabilized final, a glider pilot needs to have time on base leg to enable corrections and a turn to final within the approach wedge. So, let’s talk about solid pattern planning and the downwind leg, specifically at Harris Hill.

The purpose of any downwind leg is to:

1. Indicate to other traffic that you are about to land.
2. Take a good look at the field and choose a landing spot.
3. Check the wind by looking at the windsock and flag, also by observing wind drift.
4. Establish the proper spacing from the landing surface given any crosswind which will affect the groundspeed and time on the base leg.

The IP or initial point is the term for the beginning of the downwind leg. Calling it the initial point is bit of a legacy term and syncs up with textbooks and what other glider operations teach. Notice in the diagram below it is much broader area about the size of a small farm field in which the pilot will select a starting point given the existing wind and aircraft performance. (Editor’s note: Pattern diagrams coming soon)

The nominal altitude at the IP is 800 ft AGL. Why is Harris Hill’s pattern started at 800 ft when other glider operations teach 1000 ft or even 1200 ft? Several reasons. A higher IP altitude would be suitable for a longer downwind leg such as a 4000 ft runway. Another reason is the Harris Hill ridge, the whole reason glider operations began here. When the ridge lift quits, a pilot will realize this 800 ft AGL or lower and have to make a somewhat tighter pattern to land north. It wouldn’t do to have a higher pattern as the norm and then have everything change when someone leaves the ridge lowish. A third reason is the sink that can set up with a south wind. A higher and therefore bigger pattern can leave the glider dealing with several more seconds of horrendous sink resulting in a too low situation. The last reason is transference to off-airport landings. The cross country pilot will be rewarded often with “saves” from 800-1000 ft AGL and will continue to try to climb away at these altitudes while examining a possible landing field. Starting a downwind to an unknown farm field below 800 ft AGL, however, gets progressively dicier. So once again Harris Hill, being a cross country club, has a pattern that will serve a pilot well away from home when the time comes. (For the sake of completeness, know that cross country gliders with motors may have to start their engine even higher than 800 ft.)

This naturally and importantly leads to a discussion on the decision to land. Make a conscious decision to stop soaring and to begin landing. This should happen above 800 ft AGL with enough time to complete the before landing checklist. Punctuate the moment of decision by putting the landing gear down on a retractable gear sailplane. Once the decision is made commit to landing, all focus should be given to doing the many things necessary to accomplish the goal of a stabilized final approach.

Diagrams of traffic patterns typically depict perfectly straight downwind legs parallel to the landing runway. These diagrams often fail to show how the offset distance from varies for different amounts of crosswind. At the conclusion of the downwind leg the pilot needs to be set up for a good base leg.

Common errors included failing to do the before landing checklist before entering downwind. Distracted by this, the pilot may establish the downwind leg too near or too far from the landing zone. Another error is misjudging the crab angle needed, the glider then drifts in or out from the airport and will not be set up for a good base. Instructors often see corrections made but not aggressively enough to really change the ground track. At Harris Hill, with our prevailing westerly winds, this often means not enough distance and little to no base leg, the dreaded button hook pattern. So, continue to make effective corrections when flying the downwind leg. The ground track may not be straight as in the textbook, but the end result will be much more satisfactory.

At Harris Hill the pilot should be on downwind, opposite the touchdown reference point at 500 ft AGL for a standard pattern. Once again, we see on the pattern diagram this not a point. Rather, the glider is actively positioned nearer or further from the landing zone depending on wind and aircraft glide performance. Is it awful if the glider is 600 or even 700 ft opposite touchdown? No. Awareness of this altitude variation is helpful. More spoilers will likely be needed and/or the ground track extended. What about lower than 500 ft AGL opposite downtown? Recognizing this lower-than-normal situation, the pilot must take decisive action to shorten the remaining ground track and ensure an adequate final approach. If trending too low for the opposite touchdown position and a good final is not possible, a trip to the valley is the way to go.

A safe glider pilot must always be aware of lift and sink in the traffic pattern. Anticipate, observe, and monitor. Sink can be an anticipated anytime there is thermal activity or there is a south wind blowing off the front of the hill. A northeast wind can also induce sink with the downslope in the SW corner of the pattern to a lesser extent. Before launching on one of these days, take a few moments to observe some landings before going flying. Ask landing pilots what they experienced. When flying the pattern be looking for areas of lift and sink.

Landing a glider is a visual maneuver. Each student pilot must learn to land without the use of the altimeter before solo. Over-reliance on the flight instruments is discouraged with judgments formed by looking at the reference point. However, quick cross checks of airspeed, altimeter, and variometer are normal and helpful. Fly airspeed using good pitch attitude control, but cross check the airspeed indicator periodically. Fly the pattern by judging the relative angles to the touchdown reference point, but cross check the altimeter especially entering the downwind leg and at the 500’ opposite touchdown spot. This is helpful in identifying if the glider is trending high or low. Combine seat-of-the-pants sensations with cross checks of the variometer to be aware of significant areas of lift and sink that would require a pattern adjustment.

The landing pattern is all about setting up that good final approach. A couple points of reference at the IP and opposite downwind will aid in developing a consistent sight picture to do just that. Add in some flexible thinking about how to enter the pattern and the pilot can achieve success in varying conditions.