NTSB Identification: LAX91LA375.
The docket is stored on NTSB microfiche number 45762.
Accident occurred Saturday, August 24, 1991 in SANTA MARGARITA, CA
Aircraft: BEIERLE THUNDER GULL J, registration: NONE
Injuries: 1 Serious,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.

THE CERTIFICATED PRIVATE PILOT AND A PASSENGER WERE CONDUCTING A FLIGHT TEST OF AN UNREGISTERED, HOMEBUILT AIRPLANE. THE AIRPLANE WAS BEING MARKETED AS AN ULTRALIGHT VEHICLE WITH AN EXCEPTION OF THE ULTRALIGHT REGULATIONS GRANTED TO THE EXPERIMENTAL AIRCRAFT ASSOCIATION. THE PILOT WAS PERFORMING AEROBATIC MANEUVERS WHILE THE PASSENGER WAS FILMING THE EVENT FROM THE REAR SEAT. DURING THE PULL-UP PORTION OF AN IMMELMAN MANEUVER, THE LEFT WING FAILED AND FOLDED UPWARDS. THE PILOT DEPLOYED A BALLISTIC PARACHUTE TO CONTROL THE AIRPLNE'S DESCENT. AS THE PARACHUTE DEPLOYED, IT BECAME ENTANGLED WITH THE ENGINE PROPELLER AND WAS DAMAGED AND ONLY PARTIALLY INFLATED. THE AIRPLANE DESCENDED AND STRUCK THE GROUND AT ABOUT 50 MPH. THE AIRPLANE AND PILOT DID NOT QUALIFY FOR THE CONDITIONS OF THE ULTRALIGHT REGULATION EXEMPTION, AND THE VEHICLE IS CONSIDERED TO BE AN AIRPLANE.

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

THE FAILURE OF THE WING SPAR WHEN THE DESIGN LIMITS OF THE AIRPLANE WAS EXCEEDED BY THE PILOT. CONTRIBUTING TO THE ACCIDENT WAS AN INADEQUATE AIRFRAME DESIGN AND AN ABRUPT MOVEMENT OF THE FLIGHT CONTROLS BY THE PILOT.

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