Rockwell S 2R accident near Oakes, North Dakota, May 25, 2019
On May 25, 2019 at about 7:30 pm local time, a 1974 Rockwell S 2R, registered N4907X, was substantially damaged in an accident during maneuvering (low-alt flying) near Oakes, North Dakota. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The failure of the helical cam gear of the engine assembly due to fatigue cracks in the gear teeth, which resulted in a total loss of engine power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 25, 2019 · about 7:30 pm local time
- Place
- Oakes, North Dakota · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Rockwell S 2R No Series, built 1974
- Registration
- N4907X · no longer on the register · serial 2099R
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
The pilot was conducting an agricultural application flight in the turbopropeller-equipped airplane when the engine lost total power. The pilot maneuvered the airplane for a forced landing to an uneven field, resulting in substantial damage to the fuselage and wings. Teardown examination of the engine revealed that the teeth of the engine’s helical cam gear were fractured. Several of the gear teeth cracks showed signatures consistent with fatigue failure. The engine assembly had a relatively low time in service (485 hours) since its most recent overhaul. The helical cam gear assembly did not show pre-existing installation anomalies. The type and degree of damage to the helical cam gear was indicative of an uncoupling of the high-speed pinion from the helical cam gear of the engine torque sensor. The uncoupling event resulted in the continuous activation of the negative torque system, which likely drained the oil in the propeller and increased the propeller blade angle. This action would have resulted in an increase in engine operating temperature and subsequent loss of engine power.
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
- Loss of engine power (total) during maneuvering (low-alt flying) defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Accessory gear › boxes › (general) › Failure
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; instrument: airplane
- Flight time: 8,620 hours in all; 3,950 in this make and model; 12 in the last 30 days; 8,606 as pilot in command
- Last flight review: April 15, 2018
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: ctr
- Injury: no injuries
The aircraft
- Airframe total time: 12,813 hours
- Last inspection: annual inspection, April 21, 2019
- Maximum gross weight: 10,000 lb
- Seats: 1
- Landing gear: fixed
- Engine: Honeywell TPE-331-10 (turboprop); 485 hours total
- Operator: Bearcreek Flying Service LLC
The flight
- Departed from: 2D5 Oakes ND at 7:00 pm
- Destination: 2D5 Oakes ND
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 270° at 10 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 79°F (26°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
3 documents, released by the NTSB on February 16, 2022. 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 | NTSB Form 6120 Pilot Operator Report CEN19LA156 | PDF, 9 pages | View Download |
| 2 | Memorandum for the Record Engine Examination Findings CEN19LA156 | PDF, 3 pages | View Download |
| 3 | Photo Array CEN19LA156 | PDF, 2 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Other NTSB records under N4907X the same tail number, which may have belonged to a different aircraft at the time
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.