Thinking about towing
Posted: Wed Oct 21, 2015 12:31 pmThis blog is about the historical development of towing hang gliders in the 1970s and subsequent developments anyone would like to add.
Until now hang gliding has taken place from hills, but these are now increasingly in short supply either through overcrowding or their being closed by local authorities and landowners, even if only seasonally. In some parts of the world, such as Holland, there are no hills. The search is therefore on for other means of gaining height. For practical purposes, eliminating rockets and free or tethered balloons, the same possibilities exist as for conventional gliders—car towing, winching, aero towing, and "putting a little engine in it."
To take the last first, motorised hang gliding already appears to be practicable though early in its development. At present a McCulloch 101 engine attached to the centre section of a flex-wing and driving a 28-30in-diameter prop at the end of the keel tube, via a flexible shaft, will give a hang glider such as the Midas E a climb rate of more than 150ft/min.
Now under development is car towing as a launching method. The hang glider is towed on a vertical yoke attached to the top and bottom of the control frame, and the upper release is operated above 50ft, at which a steeper climb is safe. It could be a satisfactory method— parascenders use it for towing para-commanders and parafoil chutes.
Winching offers possibilities where the ground is unsuitable for a car, but it poses greater problems, including the shortening of the cable towards the top of the launch. This exerts a downward pull on the nose of the aircraft if the winch driver does not slow down, the wind speed increases, or the pilot tries to gain maximum height by keeping the nose high. Despite weak links, cable-cutting and back-release mechanisms, the resultant hunting, known to every glider pilot, could add up to temporary sail inversion and/or the pilot being subjected to negative g.
The problem with both towing and winching is that two people are in a position to make coincident mistakes. It might be safer on windy days to use a winching system in which the pilot carries a drum of line on the hang glider with an override friction brake, and kites himself up. The 2001b (91kg) strain involved could probably allow use of shark-fishing equipment weighing some 10-121b (4.5kg). A short hand or car tow would get the hang glider out of the ground effect, and the bottom end of the line could be pegged while the pilot worked himself up—in a smooth wind.
Aerotowing is attractive, but it is likely to be unsafe if both aircraft are movable-c.g. types with unfixed pilots, because divergency is involved. The tug would need to be either a rigid-wing ultralight with aerodynamic controls, or preferably a custom-built aeroplane that could fly safely at 25 m.p.h. (40km/hr).
When flying from a flat field, wind direction is less critical than with hill launching, and a club could have a base. This would give it a better chance to consolidate knowledge and sound practices, because more people remain for longer in the same place.
Hang gliding has come a long way in its first decade of life and now boasts a following of about 60,000 enthusiasts worldwide. It has built up an appreciable manufacturing industry, and almost half of the British production is sold abroad. The sport has created a folk art in the colouring and painting of its wings,, and it has increased by perhaps as much as a quarter the number of people in the world who fly for fun.
https://www.flightglobal.com/pdfarchive/view/1977/1977%20-%203741.html
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A lot of us, myself included, were thinking, near the end of the 1970s, about how to safely and successfully tow hang gliders. The idea was a lot simpler (and safer!) than the reality, as it turned out. I get the impression that Ann Welch, President of the BHGA, who must have had experience in towing sailplanes, was engaging in harmless speculation in the short time left before we learned about lockouts - again and again and again. To her, the potential problems seemed to revolve around pitch and angle of attack. Note that lockouts are not even mentioned in the article! Regardless, something tells me that Ann and Joe Faust would have gotten along famously.
