Beech V35B N4523A accident near Tahlequah, Oklahoma

Probable cause

A partial loss of engine power shortly after takeoff due to an inadequately tightened fuel line. Also causal was the pilot's failure to extend the landing gear once the airplane was in a position to safely land on the runway.

NTSB analysis

The pilot reported that, shortly after takeoff, about 2.5 miles from the departure airport, the airplane experienced a significant loss of engine power while climbing through 2,500 ft mean sea level. He made an immediate turn back toward the airport for a forced landing. The pilot was initially concerned that the airplane might not have enough altitude to reach the runway, and he decided to keep the landing gear and flaps retracted. The pilot stated that he became distracted with the forced landing and forgot to extend the landing gear once the airplane was in a position to safely to land on the runway. The airplane sustained substantial damage to the lower fuselage when it landed gear-up on the runway.

A postaccident engine test revealed a significant leak from a loose fuel line connection where the airframe fuel supply connected to the mechanical fuel pump inlet. After tightening the loose fuel line connection, the engine started and operated normally. The postaccident examination and testing did not reveal any additional anomalies that would have resulted in a loss of engine power during the accident flight. The engine had accumulated 10.8 hours since its most recent overhaul. It is likely that the mechanic who reinstalled the engine following the recent overhaul did not adequately tighten the airframe fuel supply line to the mechanical fuel pump inlet. The loose connection likely resulted in cavitation within the mechanical fuel pump, which provided abnormal fuel flow to the engine fuel servo, and resulted in a partial loss of engine power.

Text from the NTSB. Open the NTSB docket for CEN16LA082 for the full record.