N242CA

On April 12, 1997, at 2204 hours Hawaiian standard time, the pilot of a DeHavilland DHC-6-300, N242CA, ditched the aircraft in the Pacific ocean approximately 63 nautical miles northeast of Hilo, Hawaii, after declaring a low fuel emergency on a ferry flight. The pilot evacuated the aircraft before it sank and was rescued by the U.S. Coast Guard. He was transported to a local hospital where he was treated for minor injuries. The aircraft departed Oakland, California, at 1050 hours Pacific daylight time on an instrument flight plan to Honolulu, Hawaii. Visual meteorological conditions prevailed at the time of the accident.

The aircraft was equipped with four ferry fuel tanks in addition to the normal forward and aft internal aircraft tanks. The ferry tanks had a total capacity of 900 U.S. gallons and the normal fuel system had a capacity of 366 gallons. All four ferry tanks could be individually selected to gravity feed into either the forward or aft aircraft tank but were not instrumented for total fuel capacity. The pilot stated that all fuel tanks were filled to capacity prior to departure. Brent's International, Inc., in Hayward, California, installed the ferry tank system which was inspected by the Federal Aviation Administration (FAA) in Oakland, California. A special airworthiness certificate for the ferry flight was then issued on April 10, 1997.

After installation of the ferry tank system, the pilot flew the aircraft from Hayward to Oakland. While en route, each ferry tank was individually selected and fuel flow into the main aircraft tanks was verified. An additional test flight to check the ferry tank system for function and leaks was performed on April 11, 1997. The pilot stated that the system performed in a nominal manner.

According to the FAA ferry permit for this flight, the maximum authorized takeoff gross weight was 16,250 pounds (130 percent CTOW). The maximum quantity of fuel authorized for the ferry tank system was not to exceed 900 U.S. gallons, and the allowable center of gravity envelope was from 203.84 inches to 216.32 inches aft of the standard datum plane. In addition, the aircraft maximum operating speed (Vmo) was limited to 136 knots indicated airspeed and structural load factors of +2.5g and -1.0g were not to be exceeded.

A temporary weight & balance form was prepared by the company that installed the ferry tank system which indicated that, fully loaded with pilot, baggage, and full fuel onboard, the aircraft weighed 15,866 pounds with a center of gravity location at 208.65 inches aft of the standard datum plane. This placed the aircraft at 126.93 percent of its normally certified maximum takeoff weight.

The pilot estimated that the no wind en route flight time for the ferry flight was 16.0 hours which, by his calculations, left a 2.0 hour fuel reserve at long range cruise power settings. The proposed route of flight from Oakland to Honolulu was approximately 2,250 nautical miles with en route flight altitude winds forecast to be light and variable.

In his written report to the Safety Board, the pilot said that after 7 hours and 10 minutes of flight time, the estimated time to fuel depletion was found to be 8 hours and 40 minutes, with a time to go to destination of 7 hours and 40 minutes. Three hours later, the pilot determined that he was fuel critical due to unforecast headwinds. He declared a low fuel emergency and changed his intended destination to Hilo, Hawaii. He also requested Coast Guard assistance at that time. Approximately 4 hours later, the pilot elected to ditch under power rather than remain airborne until fuel depletion.

The pilot stated in his report of accident that there was no apparent malfunction of the aircraft or ferry tank fuel systems, and that he believed that unforecast headwinds were the primary cause of fuel depletion prior to reaching a suitable landing site.