Amateur-built OLIVER SERIES 6 accident near Big Delta, Alaska, August 25, 2023
On August 25, 2023, a 2000 amateur-built OLIVER SERIES 6, registered N151RF, was substantially damaged in an accident during enroute near Big Delta, Alaska. It was a personal flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A partial loss of engine power for undetermined reasons.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 25, 2023
- Place
- Big Delta, Alaska · map
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built OLIVER SERIES 6, built 2000
- Registration
- N151RF · registry record · serial S69912-006
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that he was about 10 to 15 minutes from his destination when the airplane sustained a partial loss of engine power. He pulled the carburetor heat on but power was not restored. He moved the throttle control from idle to full power and the engine would only increase to about 25% with full throttle. The pilot decided to make a forced landing along a treeless mountain ridgeline. During landing, a strong gust of wind lifted the airplane’s right wing and subsequently the left wing and engine impacted terrain and the airplane nosed over. The airplane sustained substantial damage to the fuselage and wings. After the accident, control continuity was established between the cockpit and engine. Although both carburetor bowls were empty of fuel, when disconnected the fuel line had fuel drain from both sides of the disconnection, consistent with fuel being fed to the engine at the time of operation. Thumb compression was established for all four cylinders. The top spark plugs all appeared to be normal; the lower spark plugs in the two right cylinders had oil in them, as did the forward right cylinder, which contained about a cup of oil. Small amounts of water were drained from the two left cylinders. The wreckage was stored unprotected outside on a trailer buried in snow and the engine was laying on it side which would account for the oil and water found in the engine. Postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. Although weather conditions were conducive to serious carburetor icing at glide power, the pilot reported application of carburetor heat after the power loss with no effect. Accordingly, the reason for the power loss could not be determined.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Nose over/nose down during landing
- Unknown or undetermined during enroute defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Engine (reciprocating) › (general) › Unknown/Not determined
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 3,865 hours in all; 100 in this make and model; 270 in the last 90 days; 73 in the last 30 days; 1,837 as pilot in command
- Last flight review: April 1, 2023
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: left
- Injury: minor injuries
The aircraft
- Airframe total time: 1,460 hours
- Last inspection: condition inspection, May 1, 2023
- Maximum gross weight: 1,550 lb
- Seats: 2
- Landing gear: fixed
- Engine: Bombardier ROTAX (ALL) (piston); 0 hours total
The flight
- Departed from: D66 Delta Junction AK at 10:30 pm
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 280° at 5 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 7,500 ft; clear
- Temperature: 64°F (18°C), dew point 54°F (12°C)
- Altimeter: 29.77 inHg
- Observation at 3:53 pm from PAFA
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
7 documents, released by the NTSB on July 24, 2024. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 11 pages | View Download |
| 2 | Carb Ice Chart | PDF, 1 page | View Download |
| 3 | Engine Examination | PDF, 11 pages | View Download |
| 4 | Mor Delay in Wreckage Examination | PDF, 1 page | View Download |
| 5 | Maintenance Records | PDF, 2 pages | View Download |
| 6 | Release of Aircraft Wreckage, NTSB Form 6120.15 | PDF, 1 page | View Download |
| 7 | Investigative Photographs | PDF, 3 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number ANC23LA070.