Beech N35 N390Z accident near Weirsdale, Florida

Probable cause

A partial loss of engine power during takeoff. The reason for the partial loss of power could not be determined due to the extensive fire and impact damage to the engine.

NTSB analysis

The airline transport pilot was departing in his airplane on a personal flight. A witness, who was a pilot and had seen the airplane take off many times before, reported that, on this takeoff, the airplane appeared lower and slower than he expected. He further noted that the engine initially sounded normal but then started to "stall" as if a cylinder was "missing." The airplane impacted tress about 1,000 ft past the end of the runway and was partially consumed by a postcrash fire. Damage to the propeller blades was indicative of some engine power being produced at the time of impact. Examination of the engine's throttle body metering unit revealed that the mixture control arm remained attached to the unit; however, when turned, it rotated on the shaft with no shaft movement. Disassembly of the unit revealed the internal splines of the throttle and mixture arms were stripped, and brass material from the bronze arms was transferred to the external splines of the steel shafts. The bronze arms should have been replaced with stainless steel arms per a service bulletin issued by the engine manufacturer 8 years before the accident. Because of impact and fire damage to the metering unit; it could not be determined if the stripped arms were the result of impact or an undertorque condition.

Text from the NTSB. Open the NTSB docket for ERA15FA308 for the full record.