NTSB Identification: LAX92LA225
Accident occurred Sunday, May 31, 1992 in TUCSON, AZ
Probable Cause Approval Date: 09/14/1993
Aircraft: SCHEMPP-HIRTH VENTUS A/16.6, registration: N8KS
Injuries: 1 Serious.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

AFTER 4.2 HOURS OF FLIGHT WHILE CRUISING AT 8,000 FT, THE RIGHT AILERON CONTROL SYSTEM 'OTELLIER FITTING DISCONNECTED. THE PILOT SAID THAT THE AILERON TRAIL POSITION IN THE AIRSTREAM CAUSED THE GLIDER TO ENTER A SPIRAL DIVE TO THE RIGHT WHICH COULD NOT BE STOPPED BY LEFT AILERON OR RUDDER. THE PILOT BAILED OUT ABOUT 1,000 FT AGL. THE GLIDER WAS ASSEMBLED ON 5/30/92 IN ACCORDANCE WITH THE FLT & MAINT MANUAL. THE GLIDER WAS THEN FLOWN FOR 4.6 HRS & PARKED OVERNIGHT. THE PILOT SAID HE LUBED THE MALE BALL FITTING PRIOR TO ASSEMBLY AS INSTRUCTED IN THE MANUAL & CLEANED & LUBED THE SLIDE LOCK PLATE WITH WD-40. THE FITTING MANUFACTURERS SAFETY MAINT INFO (NOT AVAILABLE TO PILOTS) REQUIRES THE BALL & SOCKET FITTINGS TO BE LUBED AT EACH ASSEMLBY, BUT CAUTION AGAINST ALLOWING LUBRICANTS ON THE SLIDE LOCK PLATE BECAUSE THE SLIDE 'MAY LOOSE ITS NONREVERSIBILITY' & CAUSE THE FITTING TO DISCONNECT. THE GLIDER MAINT AND FLT MANUAL DOES NOT CAUTION AGAINST LUBRICANTS ON THE SLIDE LOCK PLATE.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE INFLIGHT DISCONNECTION OF THE RIGHT AILERON 'OTELLIER COUPLER FITTING DUE TO LUBRICANTS ON THE COUPLER SLIDE LOCK PLATE, AND THE FAILURE OF THE GLIDER MANUFACTURER TO INCLUDE APPROPRIATE PRECAUTIONARY INFORMATION IN THE MAINTENANCE AND/OR FLIGHT MANUAL. FACTORS IN THE ACCIDENT WERE: THE FAILURE OF THE GLIDER AND FITTING MANUFACTURERS TO MANDATE FAIL/SAFE DEVICES FOR THE COUPLER FITTING, AND THE DESIGN OF THE GLIDER REGARDING THE FACILITATION OF THE COUPLER CONNECTIONS DURING THE GLIDER ASSEMBLY PROCESS.

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