What happened
During the descent phase of the flight, the pilot reported a loss of power in the left engine. After the pilot successfully secured the left engine, an attempt to increase power to the right engine revealed that it was failing to develop full power. Unable to maintain the necessary altitude, the pilot executed a forced landing into an open field.
The aircraft impacted trees and power lines before striking the ground. The landing was characterized by excessive speed and a long touchdown distance.
Prior to the accident, maintenance had been performed on the wing tip fuel tanks to replace drain valve o-rings. At the time of this maintenance, the wing tip tanks were empty. For the flight from Ponce to Culebra, the pilot fueled the main tanks with 5/50 gallons of aviation gasoline, bringing the total fuel load to 90 gallons. Before the return leg from Culebra to Ponce, the pilot checked the fuel levels, which showed 35 gallons in each main tank, totaling 70 gallons on board. The pilot chose not to utilize or fuel the wing tip tanks for this flight.
Findings
Investigation into the fuel system revealed that the wing tip tanks were not utilized during the flight. While the aircraft was subject to Airworthiness Directive 83-23-1, which requires checking both main and tip-tank contents and mandates a specific fueling protocol, the pilot had intentionally bypassed the tip tanks. The failure of the right engine to develop full power was the primary factor preventing the maintenance of altitude. Additionally, fuel samples taken by the FAA and port authorities from the fueling facility showed no signs of contamination.