SAFETY BULLETIN FOR HP SAILPLANES
Soaring July 1977
The following bulletin titled "HP 10, 11, 12, 13, 14, 15, 17, 18, and RS-15 Safety of Flight Service" was received by SSA from Bryan Aircraft in a letter dated May 21, 1997.
One case of loose V-tail stabilizer taper-pin spring retainer has been reported. Loss of this small 3/15" diameter pin from either left or right lower tapered pin assemblies would permit its tapered pin to loosen, retract, and allow the affected tail surface to fold upward. Such an occurrence would result in complete loss of control of the aircraft. The subject retainer pins are a press fit in the hole drilled through the base of the tapered pins and their 3/8" diameter supporting tubes. The use of hammer and pliers on these small pins to break the tapered pins loose to fold the tail is quite common. For this reason, all subject aircraft which have spring-loaded tapered pins in the lower stabilizer main spar fitting holes should be inspected before the next flight.
Any pins that can bee pulled out with hand held pliers should be removed and replaced with an AN3-6A aircraft bolt and an AN 365 self-locking nut without any washer under the bolt head or nut. Pins that are still tight should be replaced before the sailplane is flown again after the next tail-folding operation. Tight pins can be removed by clamping them tightly with Vice-Grip pliers and twisting them out.
A toll made from a 4" length of 5/16" diameter steel rod with a 3/16" hole drilled 3/8" into the end should be made. The above tool will fit onto the end of the AN3-6 bolt to make taper pin movement easy, quick and safe.
SLINGBY HP-14 FITTINGS
Soaring August 1972
Paul Bikle has sent a memo the SSA and other interested parties concerning the main spar fittings on HP-14 sailplanes manufactured by Slingsby Sailplanes. One such HP-14 broke up in flight during the Australian Nationals, and although the exact cause of the failure has not been determined, one of the single-lug main spar fittings had failed through the main pin hole. Upon learning of this the owner of another HP-14 with Slingsby fittings examined his and found one of the single-lug fittings cracked clear through to the bushing all the way across the fitting.
All other owners of such HP-14s are urged to inspect their fittings before further flight. Copies of Bikle's memo are available upon request from SSA. A stamped self-addressed envelope would be appreciated with such requests.