| Date: | Saturday 20 May 2023 |
| Time: | c. 14:00 |
| Type: |  Viking Air DHC-6 Twin Otter 400 |
| Owner/operator: | Seafly LLC |
| Registration: | N153QS |
| MSN: | 869 |
| Year of manufacture: | 2013 |
| Total airframe hrs: | 1641 hours |
| Engine model: | P&W Canada PT6A-34 |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Other fatalities: | 0 |
| Aircraft damage: | Destroyed, written off |
| Category: | Accident |
| Location: | 54 km W off Half Moon Bay Airport, CA (HAF) -
 Pacific Ocean
|
| Phase: | En route |
| Nature: | Ferry/positioning |
| Departure airport: | Santa Rosa-Sonoma County Airport, CA (STS/KSTS) |
| Honolulu-Daniel K. Inouye International Airport, HI (HNL/PHNL) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
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. 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. The flight departed STS and was destined for Honolulu International Airport (HNL), Hawaii. Satellite flight tracking data showed the airplane departed to the southwest over the ocean and climbed to an altitude of about 15,500 ft mean sea level (msl). 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.
Probable Cause:
The failure of the ferry fuel tank system to transfer fuel during a trans-Pacific flight for reasons that could not be determined, which resulted in fuel starvation and a subsequent ditching into the water.
Accident investigation:
 |
|
Sources:
sfchronicle.com
twinotterworldnews.com
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Apr-2025 07:12 | ASN | Updated [Time, Narrative, Accident report, ] |
The Aviation Safety Network is an exclusive service provided by:
Quick Links:
| ASN Home | Send Correction / Feedback |
| FSF Home | Disclaimer | Copyright |
| Contact Us | Privacy Policy |
| Press / Media |
CONNECT WITH US:
©2025 Flight Safety Foundation