KRONFELD ON GLIDING AND SOARING.pdf - Lakes Gliding Club

AUTO AND AEROPLANE TOWING 247
may be their positions. The ideal arrangement is for the
cable to be carried past the tail surfaces in a tube so placed
that the prolongation of the cable's line in normal flight runs
through the centre of gravity of the power-driven aeroplane.
The quick-release can also be placed behind the tail surfaces,
but here again the line of the cable must pass through the
centre of gravity. Moreover, great care must be taken to
prevent the cable fouling the tail surfaces when cast off.
If these two requirements are to be met fully, it would
seem necessary for the power-driven machine to be equipped
with a more or less complicated towing apparatus. But
here theory and practice are at variance, for experience has
shown that fairly simple devices will give complete satisfaction.
For beginners a fool-proof apparatus is undoubtedly
an essential, but simpler mechanisms will suffice if the
pilots of the power-driven machine and the soaring plane
know their business and take care to keep one behind the
other in a fairly straight line. In America it is often the
practice to place the quick-release somewhere on the
power-driven aeroplane's skid. This is a most precarious
position, as the cable is liable to foul the tail surfaces if the
glider rises high above its tower. The danger can, however,
be minimized by prolonging the skid sufficiently to
ensure free passage for the cable, no matter what position
the soaring plane may assume. If it is impossible to ensure
this clearance by such means, the difficulty can be circumvented
by affixing a short length of steel tubing, secured by
two clips, which will project from under the rudder. The
hook is then attached to this projection.
Aeroplanes destined to be used permanently for towing
should carry drums on which the cable can be wound.
The advantage of this is that the length of the cable between
the two machines can be varied for starting to suit the size
of the aerodrome, while the cable can also be paid out during
the flight. The shorter the cable, the more difficult will be
the work while the two machines are connected in the air,
but on the other hand it is impossible to use a long cable for
a start on a small aerodrome.
Safety measures and devices must not be neglected. As
a fairly short length of cable is generally the rule for