[Courtesy of Dick Williamson williamson "at" ll.mit.edu, October 2000]
One Sunday morning, a car pulled into the parking lot at Davis Field and a very nice women got out. After watching several sailplanes spiraling upward in a thermal, she walked over to one of the CRRC members and asked, "I was just driving by and noticed those beautiful planes up in the sky. How do you get them up there?"
"We use these electrically powered winches to tow the planes up and then we fly around looking for rising air currents."
"Does each flyer have his own winch?"
"No. One or two people bring their own winches and these other things we call retrievers. We all share the use of these pieces of equipment so we all pitch in to help the owners set up the units and pack them away at the end of the day."
Then she noted, "I see a lot of planes in the air at the same time and a bunch of pilots holding those little boxes with all of the switches and levers. How do you know that you are controlling the right plane?"
"Each of those boxes (we call them transmitters) sends out a radio signal on a particular channel and we make certain that only one flyer is on a particular channel at any time. To do this, we have that frequency board over there that has all of those numbers running up the sides. Those are the channel numbers. Before a pilot turns on his transmitter, he goes over to the board and checks to see if anyone is using his channel. Each transmitter has associated with it a thing we call a pin which is a closepin that has a tag attached indicating the flyer's name and his channel number.
A flyer clips the pin on the board over the channel number before he turns on his transmitter. If he finds that someone else has already clipped a pin over that channel number, he knows there is a potential problem. First of all, he must not turn on his transmitter or he could cause someone else's plane to crash. What he should do is talk to the other person and arrange to take turns on that channel. When two or more pilots are on the same channel, the pilot who is flying must turn off his transmitter right after landing, take down his pin, and inform the other pilots that the channel is free. That way everyone can get in the most flying time."
"Gee. I find this intricate dance rather fascinating," noted the women." "It seems that in every social situation, people evolve a set of unwritten rules that help everyone to better enjoy the experience. How do you know when it is your turn to launch?"
"Well first of all, we need to make certain that our channel is free. Then we look around to see if others are waiting to launch. There is usually some sort of informal queue of flyers waiting to launch so we inquire around us to see if anyone is waiting. Sometimes, we place our planes in a queue behind the winch, if the winches are quite busy. When we use a winch without a retriever or use a high start, we have to walk down the field to retrieve the parachute end of the towline. In that case, the person who walked down to get the tow line usually has next priority."
"I notice that when you use that retriever, someone is sitting there ready to turn it on whenever a pilot is ready to launch on the winch. Why can't you retrieve that towline at just any time? Why does there seem to be such a hurry to get the tow line in right after a launch?"
"Just after we release from tow, there is a lot of tow line and retriever line floating in the air. If we wait too long to retrieve, the lines will drape all over the field and often get tangled with planes, people, or equipment. The potential problems are worse if the planes are being launched in a strong wind. By retrieving the towline as soon as possible after release from launch, we minimize such problems. That's why the person launching always has someone lined up to run the retriever."
She looked a little worried. "Those planes fly pretty fast. How do you keep from hitting someone with a plane?"
"Avoiding a collision starts right at the launch. We make certain that no one is standing near the winch lines down field because an errant plane can veer off rather suddenly on launch. At the same time, we don't stand near the winch lines when flying. After we launch, we move away from the winch and walk some distance down field, far to one side or the other of the winch lines, so that we don't interfere with the next person to launch. Also, we want to put ourselves in position to land the plane far away from the winches, the winch lines and all of those people and planes sitting behind the winches. Landing on the winch lines just as some one is launching is a good way to destroy two planes at once!"
"I notice that those sailplanes go up rather fast when towed by the winch. How do you keep from hitting another plane in the air?"
"If another plane is flying over the winch lines, we wait until the plane is out of the way. If we are flying, we pay attention to whether someone is ready to launch and then keep the plane away from the area of the winch lines. In any case, we shout out "Launching" to warn everyone just before we launch."
Looking off to the side, the women said, "I noticed that some people are using that stretchy thing to tow their planes into the air. But it is set up off to one side. Why is that?"
"That stretchy thing is a high start. We worry that the towline on the high start may get tangled with the lines of one of the winches. When that happens, a terrible rat's nest occurs. By setting up the high start off to one side and trying to put it on the downwind side of the field, we can best avoid these tangles."
"Look at that plane over there. It seems to be going up without being attached to a towline. In fact, it looks like it has a propeller on the front. What kind of a plane is that? It doesn't seem to make much noise."
"That is an electrically powered plane so it doesn't need a tow to get it into the air. Because electrically powered planes are relatively quiet, we can fly them at this field, but we discourage people from flying the noisier gas-powered planes because they can disturb people in the neighboring houses or those taking a walk in the conservation areas which adjoin the field. We especially try to keep all of our planes, including sailplanes, away from the house which is just across from the field on the north side of the road."
"Don't you have to worry about the electrically powered planes interfering with all of those tow lines, and with the sailplanes?"
"Yes, we do. To avoid problems, people who fly electrically-powered planes move off to the east side of the field right next to that tall grass and take off from there. Do you see how the hill slopes down to the east? By taking off over that tall-grass area to the east, the electrically powered planes avoid conflict with the sailplanes. The electric planes also land away from the winches and the winch lines, just like the sailplanes. The only problem we have is when some landing targets for the sailplanes (We call these tapes.) are set up down field alongside the tall grass. In that case, the electric and sailplane flyers have to carefully coordinate their flights so no one gets hit."
As her eyes swept over the field and the wooded areas nearby, she sighed, "It must be very nice to have this beautiful and convenient field all to your selves for flying your planes."
"This is indeed a wonderful place to pursue our hobby. We do have the field pretty much to ourselves during the summer, and on those few days when it is decent to fly in the winter. However, the Sudbury Park and Recreation folks manage this area so it is open for use by anyone. During the spring and fall, the Sudbury soccer program uses the field and they have priority over anyone else. Also, we don't want to hit any kids with our planes, so we don't fly when soccer players are around."
Glancing at some of the flyers engaged in conversation, she noted, "Many of you seem to know each other rather well. Do you all belong to some kind of club?"
"Many of us belong to the Charles River Radio Controllers club which has arranged a permit with the town of Sudbury to fly here when there is no soccer activity. All of the members of our club belong to Academy of Model Aeronautics which provides insurance coverage for club members should an injury or property damage occur. We do not have exclusive use of the field. Anyone can fly here."
Do you have any formal set of written rules and a field marshal to enforce the rules?"
"Nah. We just come here to have fun and fly. We don't need any rules."
She responded, "Well, it seems to me that you may not have rules, but you do have some well-thought-out guidelines which everyone seems to understand and which make flying more enjoyable all around. This hobby of yours is fascinating. I will have to come back again and watch you fly, and do your special social dance." With that, she strolled to her car and left.