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Section 4. INSPECTION OF THE WING
The sail should be inspected once every three months or after each 50 flying hours. The
frame should be inspected once a year, after every 100 flying hours, and after every
hard landing.
4.1. SAIL CHECK-UP
4.1.1. Checking the sail surface and seams.
There should be no cuts, ruptures, threadbare holes and torn seams on the sail. Any torn
seams should be re-stitched. Cuts and ruptures on the fairing and bottom surface (BS) of the
sail that are not longer than 30 mm can be patched up with self-adhesive Dacron. The Dacron
must be of a weight of not less than 100 g/m. larger cuts and ruptures are to be repaired by
stitching on a reinforcing piece of the same fabric (stitched along the edges). Any rupture
shorter than 50 mm can be repaired in this manner, but more complicated repairs and all cuts
near the trailing edge should be carried out in the workshop of producing company. If any of
the batten tightening cords are torn or heavily worn they must be replaced.
4.1.2. Keep an eye on the sail grommets/eyelets and all areas of the sail that are subject to
extra stress, especially the keel section, the nose section of the leading edge and the outer tip
section of leading edge.
4.2. CABLE SYSTEM
The cables must be checked for broken wires and corrosion.
observed, no matter how small, the cable in question MUST BE REPLACED. It is
recommended that the entire cable system be replaced once every four years irrespective of
service conditions.
A NOTE ABOUT CABLES AND CABLE MAINTENANCE
The cables which support the wing's airframe are critical components of the wing's structure,
and must be maintained in an air worthy condition. It is a general practice in the design of
aircraft structures to design to an ultimate strength of 1.5 times the highest expected load in
normal service.
Still-17 cables, like other structural components on the wing, are typically designed with a
structural safety factor of only about 50% above the expected maximum load. No significant
loss in cable strength can be tolerated.
A cable with even a single broken strand must be replaced before the wing is flown again. A
cable which has been bent sharply enough to have taken a permanent set must also be
replaced immediately.
Some degree of fatigue due to repeated bending of cables is almost unavoidable in an aircraft
that is assembled and disassembled with every flight. Bottom side wires are subject to the
highest loads in flight, and are therefore the most critical.
17
If any defect on a wire is
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