Coming full circle

Nothing demonstrates the effect of wind on a moving aircraft's ground track like the time-tested private pilot flight test maneuver known as turns around a point. But as a flight instructor, it's not the first ground reference maneuver I teach my students.

I introduce turns around a point to the student after the first solo, for a couple of reasons: It is usually more difficult than the rectangular course or S-turns across the road and, so, the introduction is delayed until the student has more experience. In addition, it's a new and challenging wind drift correction maneuver to fill some of those dual and solo hours getting ready for the private pilot practical test.

I start the wind correction series with the student flying along and over a road with a crosswind at the flight altitude (600 to 1,000 feet above ground level) to illustrate the crab idea. After a short session of this, flown along the road in both directions, the student is then required to parallel the road each way -- at about the same distance away from the road as we would be from the field boundaries when flying the rectangular course (or from the runway if we were operating in the airport traffic pattern).

The next step, whether on that flight or the next one, is to brief and then practice the rectangular course. In the briefing, I introduce the concept of the bank angle and groundspeed in the corner turns of that maneuver.

After practicing the rectangular course the student is introduced (after another good preflight briefing) to S-turns across a road. The knowledge learned in correcting for the wind in turns around each corner of the rectangular course is used here. To best teach this, the instructor should pick as the reference a road or a tree line running perpendicular to the wind.

Turns around a point is a maneuver to maintain a constant distance from a central reference while in a turn and again brings up the fact that the angle of bank flown in the circle is directly proportional to the groundspeed.

Figure 1 on page 26 shows the idea with four airplanes flying at the points shown, tangent to a circle. This makes it clear that when headed directly downwind (position A) the (balanced) turn must be steeper.

Logic might say that position B should be the point of the steepest bank, because it appears that the airplane is being "pushed" downwind from the point. That's not the case.

One way of looking at turns around a point is shown in Figure 2 on page 26.

The heading of the airplane at various points around the circle must be such that the path is tangent to the circle when the true airspeed and wind effects are solved. The pilot does this by eyeballing the situation, although wind triangles could be worked for, say, every 15 degrees around the circle. As this figure shows, except at the points headed directly up- or downwind, the airplane is crabbing in a balanced turn.

In other words, the circle can be thought of as an infinite number of short, straight lines, and the airplane is flying one leg of a rectangular course for each one. In order to do this the airplane must be crabbed to fly the line tangent to the circle. The reason for the bank is to get the proper heading for the next "leg." The bank when headed directly downwind must be the steepest, because the airplane is approaching the next "leg" at the greatest rate. When flying directly into the wind, the opposite is true.

The airplane should be flown around the circle at a constant altitude, usually 600 to 1,000 feet agl. (This doesn't mean that the student has the freedom to fly up and down between those limits but will stick to one selected altitude.)

One common error, and a very important one to avoid, is not keeping an eye out for other airplanes that may be crossing through the area at your altitude. The student must always be aware of the wind direction (don't be surprised if your instructor decides to simulate an emergency).

There are several variations to turns around the point:

The Amoeba. Some of the circuits will resemble this shapeless, single-celled animal. The student, who isn't exactly sure of what's required but is anxious to please, varies the bank angle and radius of turn in an attempt to stay within a reasonable distance of the point. This student doesn't understand the theory of the maneuver.

The Hail and Farewell. In this one the student gradually eases away from the point until the instructor expects that another couple of turns would result in the reference sinking below the horizon. This is sometimes known as the "circular cross-country." See Figure 3.

The Roller Coaster. The student is definitely having problems with altitude. When the roller coaster is combined with the amoeba, even instructors with cast-iron stomachs have been known to throw up their hands.

Most entries to turns around a point are made when headed directly downwind and the turns are made to the left, the easiest combination, particularly when you're flying a side-by-side airplane. Right turns and entries at other points may be used for variations (and cocky students).

Turns around a point increase your confidence in flying a definite path at a relatively low altitude.

William K. Kershner has been a flight instructor since 1949. He is the author of several books, including Student Pilot Flight Manual, Advanced Pilot's Flight Manual, Instrument Flight Manual, Flight Instructor's Manual, and Logging Flight Time. A specialist in spin entry and recovery, he teaches aerobatics in Sewanee, Tennessee. Visit his Web site.