Hyannis Air Service Cessna 402C incident

In the three months prior to the incident there were no reported discrepancies by any flight crew member related to either fuel selector valve. The incident flight was the pilot's fourth flight of the day in the incident airplane. The first three flights were uneventful; however, the pilot noticed that the difference between the left and the right fuel quantities became increasingly larger during the second, third, and fourth flights when the left fuel quantity indicator was indicating a greater amount than the right. During the third flight, the pilot attempted to correct the fuel imbalance by supplying fuel to both engines from the left main fuel tank for a brief period, then returned the right fuel selector to the right tank position.

Before takeoff of the incident flight, the pilot noted a 100-pound fuel imbalance; the left fuel quantity was indicating 300 pounds and the right fuel quantity was indicating 200 pounds. While climbing to 6,000 feet, he noticed a slight right-wing-heavy tendency but did not correct it at that time. The flight continued toward the destination airport and the fuel imbalance became greater as the flight progressed. Approximately halfway into the flight, for approximately 15 minutes, the pilot repositioned the left fuel selector to the right tank position; at that time the left fuel quantity gauge indicated 300 pounds and the right fuel quantity gauge indicated between 90 and 100 pounds. After 15 minutes he repositioned the left fuel selector to its respective tank position but was not able to position it into the detent and he failed to detect that the left fuel selector was not in the detent. The flight continued toward the destination airport with both engines being supplied fuel from the right main fuel tank. As the flight approached an area called Marco Island, the pilot became concerned because the left fuel quantity gauge was indicating 300 pounds and the right fuel quantity gauge indicated 50 pounds.

He later stated that he thought the imbalance to be an indication issue. The flight continued toward the destination airport and the right engine began surging; the right fuel quantity indicator was indicating zero at that time while the left fuel quantity indicator was indicating approximately 300 pounds. He immediately moved the right fuel selector to the left tank position (crossfeed), which restored engine power; then the left engine began to surge, followed by the right engine. Unable to restore engine power in both engines, the pilot declared an emergency with air traffic control and executed a 180-degree turn towards Naples Municipal Airport. While descending he successfully feathered both propellers and landed uneventfully on runway 14 at the Naples Municipal Airport.

Following recovery of the airplane only residual fuel was noted in the fuel lines and both engine compartments, which is consistent with total fuel starvation. An adequate quantity of fuel was noted in the left main fuel tank. Postincident testing revealed the left main fuel selector would not travel into the main tank detent upon selection in the cockpit because of inadequate lubrication of the fuel selector detents. Lubrication of the fuel selector detents was not being performed by the operator due to their misinterpretation of the airplane manufacturer maintenance manual. Additionally, the operator was using an incorrect lubricant on the fuel selector gearbox. Misinterpretation of the maintenance manual also occurred with six other operators who operate the Cessna 402C airplanes. Both engines operated normally after an adequate quantity of fuel was supplied to them.

Verbatim NTSB analysis and probable cause from the NTSB dataset