Incident
During descent, the pilot reported that the airplane's left engine had lost power. He secured the left engine and added power to the right engine, but believed it was not developing full power. Unable to maintain altitude, the pilot elected to perform a forced landing in an open field. The airplane touched down long and with excessive speed, striking trees and power lines before colliding with the ground.
Maintenance and Fuel Status
A maintenance action entry in the aircraft's maintenance logbook indicated that the wing tip fuel tanks had their drain valve o-rings removed and replaced on the day before the accident. The maintenance entry stated that the wing tip tanks were empty. The pilot stated that he elected not to fuel either wing tip tank due to the recent maintenance and did not select fuel from the wing tip tanks on the day of the accident.
According to excerpts from Airworthiness Directive (AD) 83-23-1, which is applicable to the accident airplane, tip tanks are to be filled first and used last, and the pilot must check both main and tip tank contents before takeoff. The AD also requires a placard in clear view of the pilot on the instrument panel regarding fueling and takeoff procedures related to fuel tank contents. The mechanic who performed the maintenance on the wing tip tanks stated that the placard was installed and in plain view of the pilot.
Fuel Quantity and Quality
The pilot stated that he fueled the airplane with 50 gallons of aviation gasoline, for a total of 90 gallons in both main tanks for the flight from Ponce to Culebra. Prior to the return flight from Culebra to Ponce, the pilot checked his fuel quantity, which indicated 35 gallons in each main fuel tank, for a total of 70 gallons aboard the airplane before departure. Fuel samples from both the FAA and the port authorities from the facility where the airplane was fueled showed no contamination, as per the FAA Inspector's statement.
Probable Cause
The probable cause of the accident was determined to be the loss of power on the left engine and partial loss of power on the right engine for undetermined reasons, resulting in a forced landing and impact with wires, trees, and terrain during the subsequent forced landing.