NTSB Identification: NYC99LA102.
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Accident occurred Saturday, May 01, 1999 in NEW MILFORD, CT
Probable Cause Approval Date: 08/13/2001
Aircraft: Glaser-Dirks DG-400, registration: N400FJ
Injuries: 1 Minor.

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

While in flight, at an indicated airspeed of 60 knots, a 'loud bang' was heard and the gear warning alarm began to sound. The pilot looked to the left and observed the left wing displaced 20 degrees up from its normal position. The glider began to descend and control inputs by the pilot were unresponsive. In the decent, as the glider's speed began to increase, the pilot elected to egress from the glider. The glider broke apart in flight and descended to the ground. A piece of the glider's fiberglass skin that contained a residue of an adhesive on the inside surface was removed and examined. The adhesive area would have attached spar pin-lock assembly, which secured the wing spar pins. The surface of this epoxy layer contained impression marks similar to a cross-weave pattern found on the surface of fiberglass. The cross-weave pattern on the surface of the epoxy was consistent with a fracture that traveled between the UD-glass fabric tape and the epoxy layer. This separation was characterized as an adhesive separation. The surface of the epoxy layer also contained exposed voids. No bonding between the epoxy and UD-glass fabric tape was observed in the void areas.

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

The manufacturer's use of inadequate adhesive material which resulted in the de-bonding and subsequent failure of the wing spar pin-lock assembly.

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