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6.C. The Equipment




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This article is from the Hanggliding and Paragliding FAQ, by Joao Geada with numerous contributions by others.

6.C. The Equipment

The Moyes-Bailey Dragonfly is the most popular of the aerotugs. It was
designed for the sole purpose of safe aerotowing, and has a tow mast
and release mechanism built into the airframe. The horizontal
stabilizer is built low so the tug pilot has a good view in the
rear-view mirror. The special wings and ailerons afford very low speed
capabilities, even though the frame is sturdy and the engine is
powerful. Several other types of tow planes are also in use today. The
trike wing type of motorized hangglider is well suited to aerotow, and
motorized paragliders, or paramotors, have been used experimentally to
tow paragliders air-to-air at extra low airspeeds, which the other
aerotugs cannot do. All aerotowing in the United States is performed
under the USHGA aerotowing exemption granted by the FAA.

The launch dolly permits the hangglider pilot to take off from level
ground without any running, allowing him to concentrate on flight
control while the tug does all the work getting both up to
airspeed. During the rolling launch, the glider is cradled and
supported both by the basetube and the tail. The pilot is suspended
about a foot off the ground, prone in his harness. A signal is given
to the tug that the hangglider is ready, and the tug accelerates down
the runway. Castering wheels on the dolly allow it to track smoothly
in the direction of the tow. The dolly is left on the ground when the
hangglider lifts off, and usually rolls only 50 yards or so before
takeoff. Since most traditional hangglider launches are accomplished
while running upright, the prone launch off of the dolly is noticeably
different for an experienced pilot. New pilots training on aerotow
will wish to supplement their learning with bunny hill lessons for
running takeoffs.

The leash or tow rope used in aerotowing is 200 to 300 feet of
brightly colored lightweight rope. Polypropylene is what most
aerotowers use. We've found a neat little manual reeler at the
hardware shop. It's meant for extension cords and stores our 300 feet
just right. We keep two tow ropes available at all times, for those
occasions when one is accidentally dropped in a hard to find place
like Wisconsin. We also discovered (the hard way) that bright yellow
polypro becomes invisible in corn or hay fields, so we found some
neon-orange rope and hardly ever lose one anymore. It takes only
minutes to unspool a tow rope and attach it to the plane and glider.

The tow rope is symmetrical, that is, it is finished with a metal ring
at each end so that there's no front or back. The bridle (or V-line,
for its shape in flight) on the Dragonfly tow plane's tail functions
exactly like the bridle or V-line on the hangglider pilot's harness
front. They both have a release mechanism and a safety weak link, and
any way you detach, the result is a trailing orange rope and ring. We
plan on keeping the rope attached to the Dragonfly but it doesn't
always work out that way. So Rover has to be prepared to be
unexpectedly turned loose, maybe even with the leash trailing from his
collar. A hangglider pilot can wrap that rope around some anchor down
there, with hazardous results. We've lassoed cornstalks and dragged
them down the runway with the aerotug. A hangglider probably wouldn't
win that tug o' war. One should be prepared to get custody of the
rope unexpectedly, and if low, release it before it catches on
something. (If high, of course, one should bring it back and drop it
where it can be found.)

The safety weak link is a very important part of the system. Its
purpose is to disconnect the hangglider from the tug at any time the
tow forces rise above a certain level. There's one at the hang glider
end of the rope, and another slightly stronger one at the other end,
on the tug. A pilot experiencing a challenging flight, as a result of
inexperience or turbulence, will likely break a weak link before the
tow is complete. This "accidental" release often prevents a rough ride
from developing into a dangerous one, and the glider returns to the
launch area and lands.

 

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