RC Soaring
Mike Garton, 506 NE 6th St., Ankeny IA 50021; E-mail: [email protected]
I'LL START this column with a plug for the upcoming Oc-tow-berfest 2000 aerotow fun-fly and some details of last year's event.
Then will be a primer on spot-landing a glider. I'll describe a way of setting up for a spot-landing that only requires you to think about one thing at a time. The method is useful for full-house and simpler two-channel gliders.
Pete George of St. Louis, Missouri sent the pictures for this column.
Pete hosts the Great Midwest Oc-tow-berfest each fall, sponsored by the Midwest Air Wing R/C club. The event is a fun-fly for Giant Scale Radio Control (RC) sailplanes, which are towed up into the air by large RC towplanes.
Last year the event drew pilots from 12 states. More than 150 aerotows were completed, with no crashes. It takes two to tow, so that means there were more than 300 flights completed, and all models went home in one piece (figuratively, at least).
Robin Lehman of New York brought his 1/3-scale Fox Aerobatic Sailplane. The Fox was constructed from a Ripo kit. During the event, Robin performed the aerobatic routine that he flew at last year's Acro-Cup aerobatic Scale glider championship in Germany.
Robin is most responsible for the growth and popularity of aerotowing and large Scale sailplanes in North America.
In 1999, three pilots won the Pilot's Choice awards, which are determined by votes on ballots from the pilots.
There is no Scale judging. No documentation is required. The fun-fly format with Pilot's Choice awards makes for a nice, relaxing weekend.
Joe Naber of St. Charles, Missouri took home a trophy for Best Vintage Model, with his 1/4-scale ASK8 from a Flair kit.
Landon Grindstaff of Asheville, North Carolina won the trophy for Best Modern, with his 1/3-scale DG600 built from a Rosenthal fuselage. Landon scratch-built the flying surfaces for his DG600.
Rusty Rood of Pensacola, Florida was awarded the trophy for Best Towplane, flying his trusty Telemaster. Rusty's airplane was powered with a Walker 3.2 engine.
Oc-tow-berfest 2000 is scheduled for September 29–October 1. The event will be held just across the Mississippi River from St. Louis, in South Roxana, Illinois. Flying begins after the 9 a.m. pilots' meeting.
The Midwest Air Wing flying field has plenty of room, and usually has abundant thermal activity. Like last year, the field will be open for early arrivals on Thursday.
Contact Pete George for more information.
Spot landing primer
The winners at most Thermal Duration Glider contests are determined primarily by landing points.
Spot landings are usually scored with one point per second, up to the target duration. One point is subtracted for each second exceeding the target duration.
The stopping point of the landing is also scored on a bull's-eye, with points graduated from the center.
Timing and final resting position are important. The "top guns" consistently land within a couple feet of the bull's-eye, within a couple seconds of the perfect duration time.
I flew two-channel polyhedral gliders for several years, before moving to more-complex versions with flaps and ailerons. I will describe the thought process I use to spot-land a glider.
The complexity of the process may surprise you. Two-channel gliders don't just land on the spot at the right time by luck. Energy management is the name of the game. The discipline learned trying to spot-land a two-channel glider made landing full-house gliders a piece of cake.
In full-scale and RC flying, the experts will tell you they always fly a formal approach pattern. The approach is similar to flying your airplane around three sides of a rectangle; it includes a downwind leg, a crosswind leg (also called base leg), and an upwind leg ("final approach").
Separation of variables
One original idea I use to make landing easier is called "separation of variables." The phrase comes from a calculus book, but the concept is simple. Basically, you plan your model's approach so you are only worrying about one thing at a time.
My brain can do one (or maybe two) things well at a time. If I was trying to adjust your model's direction, descent angle, airspeed, timing, and position at the same time, I would be asking for trouble.
To land a glider at a specific time, you need to have a good feel for its sink rate. Most Thermal Duration Gliders have sink rates between 1.25 and 1.5 feet per second. You don't need to know the actual numeric value; use 1.5 as a ballpark estimate, and adjust it for your glider.
You can confirm these estimates with a stopwatch on a calm evening. If your model's altitude in feet divided by your time in seconds is roughly 1.5, you are on schedule.
I don't mean to imply that I do math in my head during the last minute of a Thermal Duration flight. I do memorize two or three particular combinations of time and altitude that I call "time points."
When there is one minute left in the target duration, I steer my glider to bring it close to the landing area. I position it overhead and roughly 30 feet off to the side. The one thing I am concerned with at this point is position. My attention turns to managing my model's energy. I loiter in this area and adjust the altitude so it is approximately 60 feet high, with 45 seconds left in the target duration (the first time point).
If the glider appears to be more than 60 feet high, I use flaps, spoilers, or tight turns to bleed off energy. If the model is below the target altitude, I must fly it at minimum sink speed for a while.
When there are 30 seconds left, my model should be 40–45 feet high (time point #2). Hopefully the altitude is now adjusted so that I am close to "on-schedule."
At this point in the process, I have checked the energy or time-altitude combination twice before really starting the pattern. It is nice to get this adjusted before worrying about the other stuff.
At the 30-second point, I turn my model downwind and do the first leg of the approach. If I am flying a full-house glider, I drop the flaps roughly 10°; this helps slow the approach.
The one thing I am really concentrating on during the downwind leg is getting its length right for the particular wind conditions. This leg should be short if I am flying a slow glider in a lot of wind.
Then I turn onto the base, or crosswind leg of the approach. The purpose of this leg is to get the glider directly downwind of the pilot. I just concentrate on timing the turn, so that my final approach is lined up straight upwind. Remember, I am only doing one thing at a time.
As I turn final, I line up the nose of the glider so that it is pointing at the spot, and I level the wings. Barring gusts, I do not need to turn anymore during this landing approach.
Now that the glider is lined up, I check the third and last "time point." I want my two-channel glider to be roughly 20 feet high and 15 seconds out. The time points can be higher with full-house gliders, to prevent undershooting. This is the last chance for time correction.
I choose the speed of the glider to adjust its sink rate. If a two-channel glider is too high, sometimes I make it mush, or even execute a planned straight-ahead stall. Multichannel gliders can adjust by adding or removing flap.
At most contests, the bull's-eye is worth 100 points and the time is worth one point per second. So in the last 10 seconds, I concentrate just on putting the glider down in the right place.
The model should already be lined up. The elevator is the only control I need to worry about. By checking three time points earlier, I know my time will be within a couple seconds of perfect.
Runway and "in-out spot" landings
I use a slightly different strategy for runway landings or "in-out spots." An "in-out spot" is usually a circle with full points awarded if you land anywhere inside it. In these situations, the glider has a range of acceptable landing locations.
This easier landing event makes the actual flight time much more important in the contest. Winners may have perfect scores in time and landing for each round.
In this case, I fly the final approach so I come into the landing zone a few feet high then I listen for the timer to call out the seconds. With less than one second left, I give the glider down-elevator to push it into the ground.
Flying the formal pattern and "separation of variables" should make your landings easier.
The next thing to remember is to practice, practice, practice. You can't expect to get good without it.
Transcribed from original scans by AI. Minor OCR errors may remain.
