NTSB Identification: LAX98GA110.
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Accident occurred Wednesday, March 11, 1998 in LEBEC, CA
Probable Cause Approval Date: 12/07/1999
Aircraft: Christen Industries A-1, registration: N9615G
Injuries: 1 Fatal,1 Serious.
: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.
In furtherance of the U.S. Department of Agriculture's Animal Plant Health Inspection Service (APHIS) Wildlife Services aviation program, the rear seat instructor-gunner and the front seat trainee-pilot commenced aerial hunting operations which required the trainee-pilot to maneuver at slow airspeed and low altitude while the instructor-gunner shot coyotes. The instructor was also required to be observant of the recently hired trainee's flying skill and provide any needed instruction. On previous flights, the instructor had observed the trainee experiencing difficulty maintaining altitude during turns. He also opined that the trainee was not strong enough to fully extend the wing flaps. The trainee used two seat cushions behind her back to reposition her closer to the flight controls (and the instrument panel). The instructor did not report his observations to management. During the accident flight following a coyote shoot, the trainee entered a low altitude, slow airspeed, medium bank turn to reverse course. During the turn, the instructor's attention was diverted to search the cabin floor for an ejected live shotgun shell. The instructor looked outside the airplane just as the left wing impacted the level terrain in a nose low attitude. The USDA operated the public-use airplane and directed the instructor to have it maintained by contract mechanics in accordance with FAA regulations. Contrary to the airplane manufacturer's FAA type certificate, the USDA had erroneously connected the front seat shoulder harness, with its associated inertial reel, to the back of the front seat instead of using the prescribed factory mandated location at an overhead airframe hardpoint. Additionally, the shoulder harness webbing was routed beneath seatback material. An engineering analysis revealed that due to the anchoring of the harness to the seat structure rather than the prescribed airframe hardpoint, and the nose low ground impact trajectory, the inertial crash loads to the seat increased thus exceeding its designed strength. The improper harness attachment combined with the compressive fuselage buckling resulted in the seat yielding in a forward bending direction. The trainee's head impacted the instrument panel resulting in fatal injuries. The airplane had undergone four 100-hour and an annual inspection with the harness incorrectly attached.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The trainee-pilot's failure to maintain altitude during a low level turn. Contributing factors were the pilot-in-command's diverted attention inside the airplane, his failure to report the trainee's deficient airplane handling abilities, and the shoulder harness's incorrect seatback attachment location which was not rectified during required inspections. Full narrative available
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