FlightFollowerTwin Otter ditches into the Pacific Ocean - Fuel Starvation
Accident facts and aircraft context
On 20 May 2023, A DHC-6 Twin Otter 400, N153QS, crashed into the Pacific Ocean about 54 km west of the Half Moon Bay Airport (HAF), California.
The operator reported that the airplane had a ferry fuel tank system installed for the trans-Pacific flight.
Purpose of the flight
Trans-Pacific ferry flight using an auxiliary ferry-fuel system.
Flight sequence and key events
The two aircraft main tanks were filled with fuel, then the two forward ferry bladder tanks and the one smaller bladder took on fuel.
Fueling documentation revealed that the fixed-based operator at the Santa Rosa Airport, CA (STS), added 1,189 gallons of fuel the day prior to the flight.
The airplane’s amphibious floats were removed for the flight.
About 4 hours into the flight, the crew contacted ATC and reported that they were having a fuel transfer problem and were thinking of turning around.
The crew then reported they were declaring an emergency and had 10 hours of fuel remaining but could only access about 2 hours of fuel.
About 356 miles from the California coast, the flight track reversed course to the northeast, towards STS.
About 132 miles from the coast the flight track showed a decrease in altitude to about 4,000 ft msl.
ATC advised the crew to expect a USCG helicopter to respond to their last known position and that we will come and get you. The pilot acknowledged by thanking him.
This was the last communication from the crew.
The last few minutes of the data shows an altitude drop from about 3,600 to about 240 ft msl.
The last track data point was located about 33 miles off the California coast.
The USCG responded to the scene minutes after the accident.
Examination of the wreckage in the water revealed that the fuselage was inverted, and the wings and engines had separated from the fuselage.
The Twin Otter's ferry flight became a fuel-transfer emergency over the Pacific. The crew attempted to turn back after discovering that the ferry fuel could not be accessed as expected. The subsequent descent and loss of tracking left the aircraft short of the California coast.
Investigation findings
Wreckage recovery documented the inverted fuselage and separated wings and engines, while the investigation determined that fuel starvation followed the failure of the auxiliary fuel-transfer system.
What the evidence shows
The accident was not caused by a lack of total fuel on board. The decisive problem was that the ferry system failed to make the remaining fuel usable, leaving the crew without enough accessible fuel to complete the return.
- Incident date
- 20 May 2023
- Aircraft / registration
- DHC-6 Twin Otter 400 — N153QS
- Investigation status
- NTSB preliminary/investigation record