# NTSB WPR23LA192: Viking Air DHC-6-400, N153QS, Half Moon Bay, CA, May 20, 2023 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 3 · Limited · Final report - Date: May 20, 2023, 14:00, time zone not recorded - Place: Half Moon Bay, CA · Pacific Ocean - Coordinates: 37.599193, -123.14686 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.5992&lon=-123.1469&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: Fatal - Injuries: 2 fatal - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA-FSDO - NTSB case key (mKey): 184404 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR23LA192 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/184404/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=184404 - Page: https://openairdocs.org/ntsb/WPR23LA192 ## 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fuel system: fuel storage](https://openairdocs.org/ntsb-findings/01022810): Aircraft › Aircraft systems · Inoperative (probable cause); cases with it: [Viking Air DHC-6-400, 1 case](https://openairdocs.org/ntsb-findings/01022810/cases.md?model=9502640), [All aircraft, 60 cases](https://openairdocs.org/ntsb-findings/01022810/cases.md) - [Fuel system: fuel storage](https://openairdocs.org/ntsb-findings/01022810): Aircraft › Aircraft systems · Unknown/Not determined (probable cause); cases with it: [Viking Air DHC-6-400, 1 case](https://openairdocs.org/ntsb-findings/01022810/cases.md?model=9502640), [All aircraft, 60 cases](https://openairdocs.org/ntsb-findings/01022810/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Viking Air DHC-6-400, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=9502640), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Enroute-cruise: Fuel starvation](https://openairdocs.org/ntsb-events/191); cases with it: [Viking Air DHC-6-400, 1 case](https://openairdocs.org/ntsb-events/191/sequence.md?model=9502640), [All aircraft, 733 cases](https://openairdocs.org/ntsb-events/191/sequence.md) - [Enroute-cruise: Ditching](https://openairdocs.org/ntsb-events/441); cases with it: [Viking Air DHC-6-400, 1 case](https://openairdocs.org/ntsb-events/441/sequence.md?model=9502640), [All aircraft, 186 cases](https://openairdocs.org/ntsb-events/441/sequence.md) ## Analysis The airplane was conducting a trans-Pacific flight when the accident occurred. A ferry fuel tank system was installed on the airplane and 1,189 gallons of fuel was added for the flight. About 4 hours into the flight over the Pacific Ocean, the crew contacted air traffic control (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. Satellite flight track data showed the airplane reversed course when it was about 356 miles from the California coast. About 132 miles from the coast the flight track decreases in altitude to about 4,000 ft above mean sea level (msl). The last few minutes of the data shows the altitude decrease from about 3,600 ft msl to about 240 ft msl. The last track data point was located about 33 miles off the California coast. The United States Coast Guard (USCG) responded to the accident location and reported the fuselage was inverted in the water. They reported the wings and engines were separated from the fuselage. The pilots were still strapped in their seats and unresponsive. The occupants were not recovered. Search efforts resulted in finding the nose landing gear, right wing, and right engine. A fuel bladder tank had washed ashore in southern California. Postaccident examination of the recovered components revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. A mechanic reported that he was instructed to set up the ferry fuel tank system in the accident airplane. He installed but did not fill the system with fuel, as he did not know when the flight would take place and it would have been unsafe to have the bladders contain fuel for several days before the flight. After installing the ferry fuel tank system, he contacted the copilot (who was also a mechanic), who was then to complete the installation. The mechanic understood that the copilot would be responsible for the final installation of the ferry fuel tank system and complete the appropriate logbook entries. The mechanic was not present when the copilot completed the installation and was not sure if the copilot had signed off on it. ## Factual narrative On May 20, 2023, at about 1354 Pacific daylight time, a de Havilland DHC-6-400, N153QS, was substantially damaged when it impacted the Pacific Ocean near Half Moon Bay, California, and sank. The pilot and one passenger onboard were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 ferry flight. The U.S. Coast Guard responded to the accident site. 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 Charles M Schulz-Sonoma County Airport (STS), Santa Rosa, California, 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 Daniel K Inouye International Airport (HNL), Honolulu, 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. Both occupants were visible and remained restrained in their respective seats, unresponsive. Due to safety concerns, a USCG swimmer made a limited but unsuccessful attempt to recover the occupants. The horizontal stabilizer remained partially attached to the empennage and the forward fuselage had impact damage. Wreckage recovery was not performed at this time Aerial and maritime sub-surface search efforts resulted in finding the nose landing gear, right wing and right engine. A fuel bladder tank had washed ashore in southern California. The occupants were not found. A mechanic reported that he had been instructed to prepare the ferry fuel tank system for installation in the accident airplane. He did not complete the installation due to not knowingwhat day the flight would take place. To complete the installation, the fuel bladders would have to be filled and the logbook entry would need to be completed. He stated that it would have been unsafe to have the bladders contain fuel days before the departure date. After completing the preparation of the ferry fuel tank system, he contacted the copilot, who was also one of the only individuals authorized to sign off on the installation of the ferry fuel tank system. The mechanic stated that he understood that the copilot would be responsible for the final installation of the ferry fuel tank system and completion of the appropriate logbook entries. The mechanic further stated that he was not present when the copilot completed the installation on May 19, 2023, and was not sure if the copilot had signed off on the installation. The examination of the recovered components revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. The recovered 400-gallon fuel bladder was removed from the shipping container. Jet fuel was present during the examination. The flat tube and cap were attached to the bladder and were undamaged. The top plate was damaged on one side between fasteners. No leaks of the bladder were noted. The outlet fitting attached to the top plate was undamaged and uncapped. The three longitudinal strap loops were damaged, and the straps were missing. The five tie-down lift points remained attached to the bladder on one side. Both forward and aft center tie-down lift points separated. Two tie-down lift points on the other side separated with the one remaining attached. The fuel cap was removed from the filler neck and sand was present in the flat tube. The top plate was removed from the bladder and the inside of the bladder revealed the presence of fuel and was clear of debris. The outlet fitting was unobstructed. A review of the aircraft maintenance documents shows that on February 20, 2022, a ferry fuel tank system was installed on the airplane and then removed on March 12, 2022. These logbook entries were signed by the mechanic who performed the preparation for the installation of the tanks for the accident flight. The most recent entries were not available during the investigation and were likely onboard the airplane during the flight. ## Aircraft - Registration: [N153QS](https://openairdocs.org/deregistered/N153QS-2026-03-15), registration cancelled 2026-03-15, S/N 869, built 2013 (OpenAirDocs) - Reported make and model: VIKING AIR LIMITED DHC-6-400 - Registry model: [Viking Air DHC-6-400](https://openairdocs.org/model/viking-air-dhc-6-400) (registry code 9502640) (OpenAirDocs) - Registry engine: [Pratt & Whitney Canada PT6A-34 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-34-series) (registry code 52250, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 869 - Year built: 2013 - Airframe hours: 1641.9 - Engines: Pratt & Whitney PT6-34 720 horsepower turbo prop; Pratt & Whitney PT6A-34 720 horsepower turbo prop - Damage: Substantial damage - Flight: Ferry, Part 91 - Operator: Bank Of Utah Trustee - Registered owner: Bank Of Utah Trustee - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, May 11, 2023, 0 hours before - Departed: STS, Santa Rosa, CA - Destination: HNL, Honolulu, HI - Flight plan: IFR - Equipment: Electronic primary flight display, Satellite tracking device, Stall warning system, ADS-B, Auto-pilot, Data recorder, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 65; injuries: fatal; flight instructor, airline transport; airplane ratings: multi-engine sea, single-engine sea, multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review December 25, 2021; seat: left; restraint: 4-point; flight hours: 7,140 total - Co-pilot; age 67; injuries: fatal; commercial; airplane ratings: multi-engine land, single-engine land; medical: class 2, with waivers/limitations; seat: right; flight hours: 20,000 total ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 5 knots - Visibility: 0.75 statute miles - Lowest ceiling: 700 ft broken - Temperature: 55 °F, dew point 54 °F - Altimeter: 30.17 inHg - Icing: Unknown - Turbulence: Unknown - Observed at: KHAF, 31 nm away - METAR: METAR KHAF 202055Z AUTO 30005KT 3/4SM BR BKN007 OVC013 13/12 A3017 RMK AO2= ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20230520011569A](https://openairdocs.org/incident/20230520011569A), May 20, 2023: Viking Air Limited DHC-6-400, In The Ocean La, CA, Destroyed, 2 fatal. Pilots reported to ATC engine failure due to unable to transfer fuel to the main tanks. Engines failed to operate and aircraft landed in the Ocean. Result was… ## Docket (13 files) The files NTSB released with the investigation on April 23, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=184404. 39.1 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18512096&FileExtension=pdf&FileName=6120-Operator_Redacted-Rel.pdf - Witness statement-kitti (item 2, PDF, 1 page, 5.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18483163&FileExtension=pdf&FileName=Re_N153QS%20Jim%20Kitti%20_Redacted-Rel.pdf - Email-faa sts airport visit-notes (item 3, PDF, 2 pages, 90 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18483950&FileExtension=pdf&FileName=FAA%20Notes%20on%20STS%20Visit_Redactedd-Rel.pdf - Email-initial notes on fuel system (item 4, PDF, 1 page, 86 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18484316&FileExtension=pdf&FileName=N153QS%20Fuel%20Quantities%20ferry_Redacted-Rel.pdf - Fuel tickets (item 5, PDF, 2 pages, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18523292&FileExtension=pdf&FileName=Pages%20from%20Fueling%20Documentation%20STS_Redacted-Rel.pdf - Eclipse group-final report (wreckage recovery) (item 6, PDF, 48 pages, 5.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18483746&FileExtension=pdf&FileName=Eclipse%20Group-Twin%20Otter%20Final%20Report%20PDF_Redacted-Rel.pdf - Airframe logbook excerpts (item 7, PDF, 1 page, 11.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18483539&FileExtension=pdf&FileName=Pages%20from%20Airframe%20Logbook%20Bladder%20Install%202-20-2022_Redacted-Rel.pdf - Faa-aircraft accident package (item 8, PDF, 107 pages, 5.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18513062&FileExtension=pdf&FileName=FAA%20Acft%20Ax%20Package%2023-003-ZOA-F2_Redacted-Rel.pdf - Photo array-united states coast guard (item 9, PDF, 5 pages, 402 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18484188&FileExtension=pdf&FileName=Coast%20Guard%20Photo%20Array-Rel.pdf - Flight track images (item 10, PDF, 5 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18483960&FileExtension=pdf&FileName=Flight%20Track%20Google%20Earth%20Images-Rel.pdf - Flight track raw data (item 11, CSV, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18483756&FileExtension=csv&FileName=CSV%20Raw%20Data-Rel.csv - NTSB wreckage examination summary report (item 12, PDF, 7 pages, 4 photos, 935 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18484198&FileExtension=pdf&FileName=WPR23LA192%20Wreckage%20Examination%20Summary%20Report-Rel.pdf - Pratt & whitney factual notes-redacted (item 13, PDF, 22 pages, 3.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18541392&FileExtension=pdf&FileName=23-075_N153QS%20Factual%20Notes%20Rev%201_Redacted-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.