Sportsman Technique
Sight Gauges
By Dick Lewis, Contributing Editor, Technical Tips Vol., 4, 1987-1988
Lateral sight gauges, mounted left and/or right on the wing or made of narrow strips of tape applied to the inside of the canopy, are essential to precision aerobatic flying. In Sportsman figures, vertical and 45-degree lines are judged on aircraft attitude (not flight track). The best way to set these lines accurately and quickly is by setting a lateral sight gauge line against the horizon.
Side-mounted (i.e., lateral) gauges should have a principal line set such that when it is aligned with the horizon the aircraft appears to a judge on the ground to have a horizontal attitude (not a level flight path). A good first approximation to this is to set the principal sight gauge line parallel to a line drawn from the nose to the tail (ignoring the vertical stabilizer). Most airplanes have the principal fuselage paint stripe aligned in this way.
Fine adjustment of the principal sight gauge line (and every other gauge line and spot discussed in this article) can only be done with the help of a judge, or other experienced observer, on the ground. In general, however, such fine adjustments are not necessary.
Other lateral sight gauge lines should be set at 90 degrees, +45 degrees, and -45 degrees to this principal line. It is useful to locate the center of this star pattern of four intersecting lines such that it is straight out from the pilot's eye to the horizon in both horizontal AND vertical flight. That way the pilot can hold this point on the horizon in pitch change figures (such as loops), while looking continuously to one side only (say left) and know that the wings are always level.
Wing-mounted sight gauges have the advantage that they can be used with both eyes open without parallax (double vision) problems. The principal disadvantage is that the gauge lines are short as the pilot sees them and this makes it more difficult (at least for the beginner) to quickly see small angular errors between the sight gauge lines and the horizon. Other disadvantages are the relatively high cost and the physical vulnerability of wing mounted gauges.
Canopy-mounted, narrow-tape, lateral gauges have reciprocal advantages and disadvantages. The lines can easily be made long as the pilot sees them. Thus, it is easy to quickly discern attitude errors against the horizon. You need to close one eye (say the right eye when looking left) to avoid parallax. They are cheap and virtually invulnerable. If the aircraft canopy shape is strongly curved, as in a Pitts or Eagle, it will take some considerable effort to get the tape line-layout accurate.
Wing-mounted sight gauges can also be an advantage if more than one pilot uses the same aircraft — particularly if the pilots differ in height so that their eye position in the cockpit is different. Because they are much farther away, the wing mounted gauge is much less sensitive to eye position changes than the close-up tape gauge.
Some pilots add spot gauges (or aiming points) to the front of the canopy (windshield) with small pieces of tape — sometimes of different colors for quick recognition. The idea is to place a particular spot on the horizon to quickly and accurately set some pitch attitude. A typical array of spots might be: level erect flight at cruise speed, attitude at inverted position during a slow roll (for level flight path), 45-degree upline attitude inverted (which is the same as 45-degree downline attitude erect), and attitude for very low airspeed inverted power on level flight.
To this basic array of sight gauges can be added spots of tape or visible places on the aircraft structure as initiation points. When these spots project onto the edges of the box you initiate something. Examples of this are: when this spot reaches edge of box a standard pullup will just keep aircraft in box (at standard speed, into average wind), a spot to initiate 90-degree (or more) level turn that will just keep the aircraft in the box, and a spot to cut power to initiate final slowdown and stall into a spin such that you just stay in the box. You get the idea. This way you can drive figures to the edge of the box without fear of going out.
(The information contained in the article is, necessarily, based only on my own experience and that of a few pilots in IAC Chapter One who have critiqued my articles before publication.)
EDITOR'S NOTE: Dick Lewis, IAC #11474, is the reigning Sportsman National Aerobatic Champion (1987-88). A resident of Downers Grove, Illinois, who competes in a Super Decathlon, he has now advanced to the Intermediate category this contest season. We welcome him as a new volunteer Contributing Editor writing about Sportsman competitor techniques. — Jean Sorg.
