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| eseymour@rochester.rr.com |
The technique of a safe car pulley launch or any ground Launch (winch, car or car pulley) is well described in 'The American Soaring Handbook' or the 'Joy of Soaring' or similar soaring textbooks. This set of notes is written to bring to the attention of new pilots and car drivers some of the past experiences with this method of launch and continue the excellent safety record. A good launch is made with the pilot and car driver working together to reach maximum launch altitude. The rope used at Dansville is 3/8" diamond braid polypropylene with a braking strength exceeding 2000 pounds when new. Each rope should provide from 200 to 300 launches before it is warn out. All persons that are anywhere near this rope must be aware of the fact that one end of it may be connected to a 3000 pound car with several hundred horsepower available. If the rope should become entangled with a person it could cause serious injury or death. Consider the car pulling the rope with you entangled in it across the ground at 30 to 50 miles per hour, or consider the rope crossing over a part of you at these speeds. It could cut right through. Entangled on a part of a sailplane it could cause real damage. But treated with respect the rope becomes part of a very useful method for launching sailplanes.
The most general statement that can be made is for all persons to be aware of where the rope is and what is happening to it. The car driver must consider all aspects of the launch and retrieve and must make sure that the power is applied to the rope when desired by the right amount at the right time and that power is not applied at other times. The rope must be on the pulley and not just around the pulley shaft. The area between the sailplane must be clear and the proposed drop zone must be clear. The people in the car must be inside with a good roof over each head. It is advisable to have a trained observer to watch out the back of the car to advise the car driver of any abnormality. The rope should be retrieved at a speed no greater than 10 mile per hour to prevent undue wear on the rope. Persons around the launch start line should treat the rope with respect and act as if it is attached to the car ready to go. Keep it clear of the airplane towrope. Be aware of where it is and what it could do if entangled with persons or property.
Several years ago we used a pipe driven in the ground to anchor the fixed end of the launch rope. This worked fine until the ground was softened by rain and the stake worked the ground until the stake was quite loose. Then during a launch just as the sailplane steepened its climb the stake came out of the ground and sailed through the air and hit the top of the car hard enough to put a 6-inch dent in it. If the car had been an open model it would have injured or killed the driver. The dent was directly over the driver's head. No longer is an ordinary stake used for an anchor but a steel rod anchored in 100 pounds of concrete. It is mentioned here so that any Glider Guiders that may have occasion to set up a ground launch sailplane operation, will consider the forces that are applied to the anchor and build a safe one.
During the change of operations from one end of the airport to the other due to a wind shift, a K6 was launched down wind. It made a 180-degree turn and landed. The car driver picked up the end to take it back to launch the next glider (down wind). The driver brought the car back to the downed K6 to check and make sure everything was OK. The pilot assured the driver it was. The driver then drove off at 30 mile per hour clip but the pilot and sailplane were in the loop. The pilot yelled but the driver was too far away. The pilot could visualize the rope cutting the sailplane in two and picked up the now fast moving rope juggling it over the tail and trying to juggle it over the wing, but in the process was tossed over the wing himself. The rope caught between the aileron and wing tip and swung the sailplane around. The pilot landed on his shoulder, which was injured, and the K6 required minor repairs. Considering the situation, the pilot could have been killed and the K6 could have been damaged beyond repair It is good practice and should be a rule that:
Several times during operations the rope has been near people and property during takeoff. In one case a sailplane was being returned to the start line and the wing walker had to hold the rapidly moving rope away from the sailplane with a shoe on his foot. It is not necessary to say anything further about this dangerous situation. In the second case the rope was under a wing of a 2-33 sailplane when the launch started, with several people attempting to retrieve the 2-33 and return it to the start line. The sailplane being launched became airborne before anyone was aware of the situation. The pilot released and landed. The rope caught between the wing and aileron and spun the 2-33 around, causing more than $100 damage. Fortunately no one was injured. In the third case an airplane was landing on the cross-runway when the launch started. The pilot of the sailplane saw the airplane in time, and remained low while the airplane rolled out over the rapidly moving rope. When the airplane was safely beyond the rope the pilot pulled up and completed the launch. In this case the flagman and car driver were negligent; the flagman for not noticing the traffic and holding the launch and the driver starting the launch with moving traffic on the cross runway.
Several times airplanes have taken off and passed within only a few feet of the rope that was still connected to a sailplane about 1000 feet over the tow car. One airplane made a long straight-in approach having been way out when the launch started and was undetected by the flagman. The airplane came over the approach end of the field at better than 100 miles per hour and made a low pass but did not touch down, then climbed out well past the rope before it was dropped by the sailplane. The airplane pilot was completely unaware that a rope could have become entangled with his airplane and spoiled his entire day (ours too). The second airplane was on the down wind leg of his landing pattern when the launch started. The airplane made a shorter than usual pattern followed by a 'touch and go'. This airplane missed the rope by only a few feet. Several times an airplane started a take-off from a position near the center of the runway, (sometimes opposite the car launch start line), and seem to be completely unaware of the consequences of becoming entangled with the rope. One airplane did fly under the sailplane and cut the rope with his propeller. In this case the pilot landed and came to give us hell but one of our members beat him to it by asking how come he cut our expensive rope with his propeller. He was taken aback. Fortunately the rope was directly in line with the propeller. If it would have been a little to either side it could have caused him to crash. Need I say more? In the above situations the flagman has long since committed the launch and can do nothing except observe the action. The sailplane pilot is concentrating on his part of the launch with the potential danger approaching from the rear. The car driver is concentrating on keeping the car under nearly full power and may not see (will not see) the approaching airplane. However a trained observer in the car could warn the driver of the approaching aircraft and the driver could take one of several actions:
Most releases are designed so that if you overrun the rope it will automatically release. This does not al ways happen on the ground launch. When you are at the top of the launch and are pulling several 'Gs' the rope is pulling down and not back. Consequently, you may be pulled over the top and then into the ground at the end of a long arc. (There are two deaths that I am aware of due to this situation) The fix for this is to initiate a turn as soon as you find that you cannot release. (We have a live one in this case where the pilot turned a couple of circles about the tow car and then flew over the top of the tow car and got next to the ground before he came to the end of the rope. But he was going parallel with the ground when he reached the end of the rope, and the rope broke with no upsets) Consider you being pulled down in a great arc with you against the straps trying to operate the release, with several 'Gs' making the release difficult to open. Keep in mind there is an out if you respond quickly. The other out is the ground crew realizes your predicament and cuts the rope. We did have one where the upper ring was driven back into the fuselage on a rope brake, and caught in the v shaped fuselage structure. There was a parachute that indicated to the pilot that something was wrong. The ground crew did cut the rope. But the long rope dangled out over the phone wires at the end of the airport, then over a field then over a woods and finally into the airport. All the while the pilot was pulling on the release handle trying to get away from the parachute that was flapping on the left side of the sailplane. Fortunately the crew cut the rope and the rope did not tangle with anything. Lets not let this happen to us.
Make sure: the rope is properly placed over the pulley,(one tow with the rope around the shaft and the rope is useless thereafter) the path of the car and sailplane are clear, proper driver technique is used for the launch and rope retrieve, all persons at the car are inside and properly seated, you are prepared to quickly cut the rope if required, you have insured that no person or property is in the loop during retrieves.
Make sure: pattern is clear enough to complete the launch, the cross runway is clear of traffic, the takeoff area is clear; the rope is properly attached to the sailplane after the pilot indicates that he is ready
Make sure: sailplane is airworthy and you have completed you checklist, takeoff area is clear, cross-runway is clear of traffic, proper flying technique is used during launch with preparation for rope brake at any time.
Car pulley launch is a reliable, inexpensive, safe method of launching sailplanes. A safe operation depends upon each person involved being AWARE of the action around him and using common sense to prevent dangerous situations from arising with a prepared course of action ready for any emergency.