Right Fuel Selector Valve Was Corroded, Which Most Likely Resulted In The Right Engine Fuel Flow Fluctuations

Location: Sherman, Texas Accident Number: CEN23FA284
Date & Time: July 8, 2023, 09:41 Local Registration: N4743M
Aircraft: Piper PA-30 Aircraft Damage: Substantial
Defining Event: Loss of control in flight Injuries: 1 Fatal
Flight Conducted Under: Part 91: General aviation - Personal

Analysis: The multi-engine airplane was in level flight at 5,000 ft on a north heading toward the destination airport. Onboard data indicated the right engine’s fuel flow fluctuated for about 15 seconds. About 20 seconds later, the left engine fuel flow reduced to zero. The airplane made a slow descent toward the east for about 9 minutes, away from the destination airport. The airplane then turned west back toward the airport and continued a slow descent. About 10 minutes later, the airplane was less than 100 ft above ground level, with a groundspeed of about 61 knots. The airplane turned left about 40° during the last 4 seconds of recorded data and subsequently impacted a field with a nose-down attitude. The airplane sustained substantial damage to the fuselage, empennage, and both wings. 

Postaccident examination of the airplane revealed the left engine’s fuel selector was in the off position and right engine’s fuel selector valve was in the main tank position. The right fuel selector valve was corroded, which most likely resulted in the right engine fuel flow fluctuations. It is possible that the pilot moved the left engine fuel selector from auxiliary tank to off inadvertently when he intended to move the right engine’s fuel selector from the auxiliary tank to the main tank.

The left-engine propeller was not feathered at the accident site, which resulted in additional inflight drag and a higher minimum controllable airspeed (VMC).  During the attempted forced landing, the pilot failed to maintain adequate airspeed, which resulted in a loss of control and a nose-down impact with terrain. The pilot’s toxicology results indicated use of the sedating antihistamine medication diphenhydramine, and he may have experienced associated impairing effects at the time of the accident. More precise interpretation of the diphenhydramine level in cavity blood was not possible. The pilot also had used other drugs that may have had adverse side effects (yohimbine, as well as both tadalafil and tamsulosin), although there was no way to determine whether such side effects were present or significant. The investigation was not able to determine the role the pilot’s medication usage may have played in the accident sequence.

Probable Cause and Findings: The National Transportation Safety Board determines the probable cause(s) of this accident to be -- The pilot’s failure to maintain control during a forced landing following a loss of engine power. Contributing was the pilot’s failure to feather the left propeller following the loss of engine
power. 

FMI: www.ntsb.gov