Aviation Accident Summaries

Aviation Accident Summary SEA97LA011

TILLAMOOK, OR, USA

Aircraft #1

N7150A

Aero Vodochody Aero. Works L-29

Analysis

The Checkoslovakian manufactured Aero Vodochody L-29 jet trainer collided with terrain following a loss of control while maneuvering at low altitude. Before the accident, the aircraft was maneuvering into position to photograph an F4F Wildcat aircraft. Witnesses reported that the aircraft took off and maneuvered to overtake the Wildcat. They stated that as the L-29 crossed behind the F4F's flight path, it rolled to the right, approximately 1-1/4 turns. Reportedly, the L-29's nose pitched up during the occurrence, then dropped to an extremely nose-low position. The aircraft subsequently impacted the ground in a near level attitude with a steep flight path angle. The witnesses reported that the sequence took place at an estimated airspeed between 120 and 150 knots and about 500 feet above ground level. The witnesses also reported that the two aircraft did not collide. A guide to world military aircraft gives the airplane's flaps-down stall speed as 81 MPH (70 knots) at 7165 pounds gross weight. One witness stated the pilot had performed a 'barrel' roll type of maneuver; the witness believed this was an intentional maneuver to slow down, as he was overtaking the F4f. The investigation did not determine whether the aircraft had encountered wake turbulence, or whether it had stalled and/or dished out during the maneuver.

Factual Information

On October 11, 1996, approximately 1617 Pacific daylight time, an Aero Vodochody L-29 Delfin, N7150A, registered to the Erickson Group Ltd. of Beaverton, Oregon, collided with terrain following a loss of control while maneuvering at low altitude in the vicinity of Tillamook Airport, Tillamook, Oregon. The commercial pilot and a passenger were fatally injured, and the experimental-category airplane, a Czechoslovakian-manufactured two-seat military jet trainer retrofitted with a Pratt & Whitney J60-5 engine, was destroyed. The 14 CFR 91 flight was planned as a local flight out of Tillamook. Visual meteorological conditions prevailed and no flight plan had been filed. A representative of the operator stated that the passenger was a photojournalist for an aviation publication and that the flight was being conducted as a photographic mission for the passenger. At the time of the accident, the aircraft was maneuvering into position to photograph an F4F Wildcat aircraft. Witnesses reported that the aircraft took off and maneuvered to overtake the Wildcat. They stated that as the L-29 crossed behind the F4F's flight path, it initiated a roll to the right, rolling approximately 1 1/4 turns, and that the L-29's nose then pitched up, then dropped to an extremely nose-low position, and that the aircraft subsequently impacted the ground in a near level attitude with a steep flight path angle. The witnesses reported that the sequence took place at an estimated airspeed between 120 and 150 knots and about 500 feet above ground level. The witnesses also reported that the two aircraft did not collide. A guide to world military trainers published in the magazine of the Air Force Association (John W.R. Taylor & Kenneth Munson, "World Gallery of Trainers", Air Force Magazine, December 1995) gives the L-29's flaps-down stall speed as 81 MPH (70 knots) at 7,165 pounds gross weight. FAA investigators conducted an on-site examination of the aircraft wreckage on the day after the crash. They reported that they did not find any evidence of malfunction in either the airframe or the engine. The operator, Erickson Group Ltd., failed to return a completed NTSB Form 6120.1/2, Pilot/Operator Aircraft Accident Report.

Probable Cause and Findings

failure of the pilot to maintain control of the aircraft, while maneuvering behind an F4F aircraft. The lack of altitude for a recovery was a related factor.

 

Source: NTSB Aviation Accident Database

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