Beech C35 accident near Rock Springs, Wyoming, July 20, 2023
On July 20, 2023 at about 6:55 pm local time, a 1951 Beech C35, registered N620D, was substantially damaged in an accident during enroute near Rock Springs, Wyoming (Southwest Wyoming Regional Air airport). It was a personal flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
Maintenance personnel’s failure to properly secure the propeller pitch control rod castellated nut hardware, which resulted in an in-flight failure of the pitch control bearing and subsequent loss of engine RPM and thrust.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 20, 2023 · about 6:55 pm local time
- Place
- Rock Springs, Wyoming · Southwest Wyoming Regional Air · map
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Beech C35, built 1951 · all C35s on the register
- Registration
- N620D · registry record · serial D-2879
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot was conducting a personal cross-country flight in the single-engine airplane when the accident occurred. During the flight the pilot and passenger heard a pop sound from the engine. The passenger thought he saw something fly up from the engine and they subsequently saw some residue stuck on the windshield. The passenger described it as five small black specs of a thick viscosity. A few minutes later the airplane could not maintain altitude and the engine rpm had a slight drop even though all of the engine indications were still in the green. The pilot decided to continue to his destination airport. After maneuvering at the destination airport, the maximum engine rpm decreased to 1,250 rpm. The pilot declared an emergency and switched runways; however, due to airport ground traffic, he decided to land off-airport. The airplane contacted powerlines and the ground during the landing. Examination of the wreckage revealed that the propeller pitch control bearing forward cage and ball bearings had separated and were not found with the wreckage. The bearing inner and outer races were covered in a dark residue. The castellated nuts on the actuator bearing assembly remained attached to the pitch change bolts. However, the nut on the No. 1 pitch control rod had backed out of place and sustained mechanical damage. A cotter pin was not found in the nut. The nut on the No. 2 pitch control rod remained in place and a cotter pin was installed in the nut. The damaged nut was positioned adjacent to the propeller pitch control bearing assembly. The actuator bearing assembly was positioned unevenly on the hub assembly. Based on this evidence, the damaged castellated nut was likely not properly installed with a cotter pin. The missing cotter pin allowed the nut to back off to the end of the pitch change bolt, resulting in contact and catastrophic damage to the propeller pitch control bearing. It is likely that the unevenly positioned pitch control rods resulted in a reduction of RPM and thrust. The actuator bearing assembly was removed from the hub; the attachment hole and surrounding area for the No. 1 pitch control rod was covered in a dark oily residue. The No. 2 pitch control rod attachment hole showed clean surfaces. Therefore, the No. 1 pitch control rod was likely loose for some time, resulting in the dark oil residue in the attachment area.
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
- Part(s) separation from AC during enroute (climb to cruise)
- Loss of engine power (partial) during enroute defining event
- Loss of engine power (partial) during maneuvering
- Collision with terrain or object (not controlled flight into terrain) during emergency descent
The NTSB's findings
- Personnel issues › Task performance › Maintenance › Installation › Maintenance personnel
- Aircraft › Aircraft propeller/rotor › Propeller system › Propeller controlling system › Incorrect service/maintenance
Pilot
- Certificate: private
- Ratings: single-engine land; instrument: airplane
- Flight time: 554 hours in all; 155 in this make and model; 34 in the last 90 days; 1 in the last 30 days; 496 as pilot in command
- Last flight review: January 21, 2023
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: minor injuries
Passenger
- Seat: rgt
- Injury: minor injuries
The aircraft
- Airframe total time: 3,274.5 hours
- Last inspection: annual inspection, December 17, 2022; 95 hours since
- Maximum gross weight: 2,700 lb
- Seats: 4
- Landing gear: retractable
- Engine: Continental Motors E-225-8 (piston); 3,370 hours total
The flight
- Departed from: KVGT Las Vegas NV at 3:39 pm
- Destination: KRKS Rock Springs WY
- Flight plan: IFR
- Runway 3, 5,228 ft by 75 ft
Weather at the time
- Light: daylight
- Wind: from 350° at 4 knots
- Visibility: 10 statute miles
- Sky: overcast at 16,764 ft
- Temperature: 20°F (-7°C), dew point 9°F (-13°C)
- Altimeter: 30.42 inHg
- Observation at 12:43 pm from KRKS
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flig | 1 | |||
| Passengers | 1 |
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 docket at the NTSB holds the report as a PDF and the investigation's photographs and documents. This site 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 WPR23LA283.