Active Base Leg

Once safely back at the field, the pilot immediately turns his or her attention to a stabilized final to a well selected touchdown spot. When landing at a short field, like Harris Hill or in an off-airport situation the base leg is crucial to setting up that ideal final approach.

A look at scary landings at Harris Hill over the years will reveal that a large majority are the result of being too high or low on final. But a closer look, say from the instructor’s seat, reveals that bad final approaches are really the result of bad base legs or worse, no base leg. Rule number one when planning a good base leg is: fly a pattern in order to have sufficient time on base leg to adjust your height.

So how does a pilot with no motor crack the problem of not getting stuck short of the field without ending up too high? Struggling to get back to earth at our little airport in a high-performance flying machine can be frightful without the proper skills. Well, the FAA is no help on this. The FAA culture is born out of airplane flying and all their publications depict perfectly rectangular traffic patterns. Instead, we should look to the British Gliding Association and their excellent instructor’s manual. They teach the way a glider pilot should actively make adjustments on the base leg to turn final at the right approach angle.

One of the hardest things for student pilots to learn is when to turn onto base leg. The power pilot’s answer is a pat “when I look back over my shoulder 45° it’s time to turn final.” That’s nice if one has an engine but assuming the landing in question is a normal, into-the-wind glider approach, this is too far away from the field. The truth is it is very hard to guess the exact point to turn base for a perfect pattern. There are too many unknowables - so make this downwind-to-base turn conservatively. Look back at your reference point and turn a little early, erring on the side of reserving a little extra altitude.

Here is another helpful tip. When turning from a well-planned downwind to base, make crisp turn with a healthy bank angle, 30-35°. Get into this turn and get out with a proper crab angle established. Get those wings level and look at the touchdown reference point to form high/low judgments right away. The pilot must consciously not to let the nose come up in these pattern turns. A straight yaw string is essential.

Once on base leg the pilot must be super alert. Continue to be aware of lift and sink. Pilots should look at the touchdown reference point throughout the pattern, especially on the base leg. Be active on the dive brake handle; full dive brakes, no dive brakes, or some partial amount of dive brakes. Which is appropriate?

A square base leg is for suckers. A base leg with a ground track perpendicular to final will happen more and more often with experience. However, doggedly trying to make a square pattern is the number one reason gliders end up turning final turning too high or too low. This is called being above or below the approach wedge and will result in an unstable final approach or a stall short of the field.

When pilot senses the flight path is trending too low, the base leg must be edged in closer to the field. The extreme case would require a ground track aimed at the nearest corner of the airfield until things again begin to look normal. Early recognition of being too low is the key and will allow for a more subtle edging in.

But as was stated, the preferred way to plan the base leg is to turn downwind to base slightly early to guard against sink. In the process of ensuring adequate height for a good final the pilot may encounter no sink or even lift. It is therefore essential to have skills to get rid of excess altitude before turning final. Again, time is the key to turning any sink rate you can develop into a real altitude adjustment.

Again, the FAA has done us no favors. Each private pilot candidate for their flight test must turn onto final without overshooting the final. It is in the FAA’s practical test standards and we train to this standard. That is all nice for airplane pilots who can do a go-around if things don’t look right. Forcing a turn onto final too high in a glider can have disastrous results. In fact, ugly landings at Harris Hill are about 2:1 in favor of too high versus too low.

So, we need not only good pattern planning but a bag of tricks to lose altitude when high before committing to the final approach. In this way we can keep that last 200 feet of final straight-in and on-speed.

• The first thing to do when approaching final and too high may seem obvious; open the dive brakes all the way and keep them there until you are back down within the useful range of dive brake effectiveness.
• If the glider is still slightly high, the second trick is square the base to final turn (with full dive brakes.) This little extra bit of ground track is surprisingly helpful for small corrections.
• The next trick is a personal favorite. If the base leg is obviously trending too high, edge out. The dive brakes are full open during this maneuver. The subtle version is to just let the wind drift you further from the field as you are on base leg. When in the approach wedge, a turn to final is made as normal. The more aggressive version of edging out is simply turning to amend the base leg ground track outward. This is very comfortable for passengers, there is no flying through final, so it is also useful for an FAA check ride.
• If the glider is still above the approach wedge do not turn onto final. Rather, continue through final with a shallow S-turn or a full reverse base. Still too high? Edge out on the reverse base leg.
• Lastly a word about a 360° turn on final. Turning your back to the field during landing is definitely a no-no. If a 360 is needed to get down, a debriefing is in order as this is a result of serious lack of pattern planning. It is better than flying off the back of the hill, however. I’ve never seen a 360° turn executed while someone was landing north at Harris Hill. This is probably because all north landings have some headwind. We default to a south landing if winds are calm or crosswind. If landing south and a 360° turn appears to be necessary, first turn 180° toward the valley and assess the situation, as if to rejoin the downwind leg. Is another 180° of turn, in the form of another base and final, going to put the glider solidly in the approach wedge? Maybe, maybe not. If the answer is no, go to the valley and set up a new pattern at the aux field.

So, as we see the base leg is not simply a connector from the downwind to final, as it is in airplane flying. There must be active decision making and effective flight path corrections happening on base leg to ensure a turn onto final within the useful range of the spoilers, within the approach wedge.