| Date: | Saturday 8 April 2023 |
| Time: | 19:37 |
| Type: | Van's RV-7 |
| Owner/operator: | Private |
| Registration: | N17NK |
| MSN: | 73089 |
| Year of manufacture: | 2021 |
| Total airframe hrs: | 133 hours |
| Engine model: | Ivchenko%20AI-25TL |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Other fatalities: | 0 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | near Morgan, UT -
United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Bountiful-Salt Lake Skypark, UT (BTF/KBTF) |
| Destination airport: | Bountiful-Salt Lake Skypark, UT (BTF/KBTF) |
| Investigating agency: | NTSB |
| Confidence Rating: | Accident investigation report completed and information captured |
Narrative:On April 8, 2023, at about 1937 mountain daylight time, an experimental amateur-built Van’s RV-7, N17NK, was substantially damaged when it was involved in an accident near Morgan, Utah. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot reported he noticed an odor of burning oil shortly after takeoff. About a minute later, the airplane began to shake, oil covered the windscreen, and the propeller separated from the crankshaft. The pilot performed a forced landing in a snowy field, and during the landing roll the airplane nosed over and came to rest inverted. The propeller assembly was found in a field about two miles away.
The most recent condition inspection was completed by the pilot one week before the accident flight, and the airplane had accrued three flight hours since the inspection. Although brass flakes were observed in the engine oil during the condition inspection, engine data recovered from the airplane's multi-function display was consistent with normal engine operation.
Five of the six propeller bolts were recovered and examined after the accident. The examination revealed fatigue cracks in multiple areas on each bolt that progressed until each bolt failed in overstress. Additionally, two of the recovered bolts displayed more extensive fatigue features than the other three bolts that were examined.
The pilot documented that he had removed, inspected, and reinstalled the propeller during the condition inspection. Given this information, it is likely that the pilot/builder had not torqued all the propeller attachment bolts to the correct value, resulting in the progressive fatigue failure of the bolts.
Probable Cause: The pilot/builder improperly torqued the propeller attachment bolts while reinstalling the propeller, which resulted in the fatigue failure of the bolts and the separation of the propeller assembly.
Accident investigation:
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| Investigating agency: | NTSB |
| Report number: | WPR23LA149 |
| Status: | Investigation completed |
| Duration: | 1 year and 10 months |
| Download report: | Final report
|
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Sources:
NTSB WPR23LA149
https://data.ntsb.gov/Docket?ProjectID=107032 https://registry.faa.gov/aircraftinquiry/Search/NNumberResult?NNumbertxt=17NK https://flightaware.com/live/flight/N17NK/history/20230409/0138Z/KBTF/15UT Location
Images:

Photo: NTSB
Media:
Revision history:
| Date/time | Contributor | Updates |
| 09-Apr-2023 18:21 |
Captain Adam |
Added |
| 01-Mar-2025 12:57 |
ASN Update Bot |
Updated [Time, Operator, Other fatalities, Source, Narrative, ] |
| 02-Mar-2025 19:48 |
Captain Adam |
Updated [Time, Source, Narrative, Photo, ] |
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