Accident Sequence
A lineman reported that the parking brake was set before the flight. The pilots began takeoff on a 5,147-foot runway with a 10-knot crosswind. A witness observed the aircraft rotate for takeoff approximately 4,500 feet down the runway and lift off about 50 feet later. After lift-off, the aircraft remained low and slow, between 20 and 60 feet above ground level. It then banked left and right in a nose-high attitude, settled, struck trees, and crashed about 200 feet beyond the runway end. One person stated that the aircraft went out of control before impact; another said it was "in or on the edge of stalled flight."
Aircraft and Pilot Information
The accident aircraft was an early model Learjet 23, serial number 23-45a. On this model, the parking brake had to be released by first depressing the brake pedals; the pilot operating handbook did not address this procedure. On later models (serial numbers 23-050 and up), releasing the parking brake required only moving the control to "off." Investigations revealed that the left-seat pilot had training in later models (Learjet 24/25), but only a biennial flight review was noted for the Model 23. The company dispatcher indicated that no training would have been performed on the accident flight, which carried a passenger. The aircraft was approximately 430 pounds over its maximum weight limit.
Examination Findings
Post-crash examination showed rotational damage occurred in both engines during impact. The braking systems exhibited evidence that the parking brake control valve was partially engaged; the brake torque tube contained heat blueing, indicating elevated temperatures.
Probable Cause
The official probable cause of the accident was: Improper preflight by the pilot, his failure to abort the takeoff while there was sufficient runway remaining, and his failure to assure that the aircraft attained sufficient airspeed for lift-off and climb. Factors related to the accident were: the pilot's failure to assure the aircraft was within its maximum weight limitation, his improper use of the parking brake, and insufficient information in the pilot operating handbook concerning the aircraft parking brake.