# NTSB WPR23LA283: Beech C35, N620D, Rock Springs, WY, July 20, 2023 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: July 20, 2023, 12:55 local (18:55 UTC) - Place: Rock Springs, WY - Coordinates: 41.600733, -109.0512 - Nearby events: https://openairdocs.org/map.md?lat=41.6007&lon=-109.0512&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA-FSDO, Textron Aviation - NTSB case key (mKey): 192689 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR23LA283 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192689/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192689 - Page: https://openairdocs.org/ntsb/WPR23LA283 ## Probable cause 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Beech C35, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=1151508), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Propeller system: propeller controlling system](https://openairdocs.org/ntsb-findings/01046120): Aircraft › Aircraft propeller/rotor · Incorrect service/maintenance (probable cause); cases with it: [Beech C35, 1 case](https://openairdocs.org/ntsb-findings/01046120/cases.md?model=1151508), [All aircraft, 25 cases](https://openairdocs.org/ntsb-findings/01046120/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-climb to cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338); cases with it: [Beech C35, 2 cases](https://openairdocs.org/ntsb-events/338/sequence.md?model=1151508), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Enroute: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Beech C35, 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=1151508), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Maneuvering: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342); cases with it: [Beech C35, 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=1151508), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Beech C35, 6 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1151508), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis 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. ## Factual narrative On July 20, 2023, about 1255 mountain daylight time, a Beech C35 airplane, N620D, was substantially damaged when it was involved in an accident near Rock Springs, Wyoming. The pilot and passenger sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal cross-country flight. The pilot reported that during the flight he activated an instrument flight plan and climbed to 15,000 ft mean sea level (msl) to get above the clouds. During the climb the pilot and passenger heard a pop sound from the engine. The passenger thought he saw something fly up from the engine that subsequently stuck on the windshield. The passenger described it as five small black specs of a thick viscosity. The pilot checked all of the engine instruments, which were in the green. About 5 minutes later, the airplane could not maintain altitude and was cleared down to 14,000 ft msl. The engine rpm had a slight drop, and all the engine indications were still in the green. At this point the pilot decided to continue to his destination airport. After the airport was in sight, he cancelled the instrument flight plan and entered a straight-in approach for runway 3. About a mile from the airport, he noticed that he was too high for the approach and performed a slipping maneuver for about 3 seconds to decrease altitude. He stopped the maneuver before getting to his desired altitude because of the uncomfortable descent rate. The engine rpm was now 1,250 rpm, and he declared an emergency and announced that he was now landing on runway 27. His altitude had dropped considerably, and he decided to land on a taxiway but then saw an airplane holding short of the runway and opted to turn left for an off-field landing. The airplane impacted powerlines and subsequently impacted the ground. The powerlines were about 300 ft northeast of the main wreckage. The data from an onboard engine monitoring instrument was downloaded and revealed the entire accident flight. The data showed a drop of rpm from 2,500, while the airplane was at about 15,000 ft, and for the remaining flight the rpm remained between about 1,600 and 2,300. During the last 15 minutes of the flight, the rpm dropped then spiked about 3 minutes before the end of the data, along with an immediate rise in manifold pressure. A postaccident 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. One of the nuts was secured to the bolt with a cotter pin and the other nut was attached to the bolt and had mechanical damage. Threads were visible below the damaged nut and a cotter pin could not be identified. The damaged nut was positioned adjacent to the propeller pitch control bearing assembly. The actuator bearing assemblywas positioned unevenly on the hub assembly. (See figure 1.) Figure 1. Actuator bearing assembly and the No. 1 pitch control bolt and nut. The brass-colored metallic material was removed from the damaged No. 1 pitch control rod castellated nut. (See figure 1.) The end of the pitch control bolt was visible halfway through the nut. The nut was removed, and the castellated side of the nut was damaged. The cotter pin was not found, and the bolt’s cotter pin hole was clear. The No. 2 pitch control rod castellated nut was secured with a cotter pin. The actuator bearing assembly was removed from the hub and 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. The No. 1 blade was removed from the hub and grease was noted throughout the interior. Both yoke lock nuts remained secured to the pitch control bolts and were safety-wired. The No. 1 pitch change block was undamaged. Both pitch change blocks had stamped numbers “1” and “2” but were found on opposite blade pitch assemblies. The No. 1 blade ball bearings and race halves were cleaned and their surfaces showed light spalling signatures. The No. 2 blade was removed from the hub. The pitch change block (blade bushing) remained attached to the hub end and the pitch change block, bolt, and yoke had impact damage. Grease was noted throughout. The No. 2 blade ball bearings and race halves were cleaned and their surfaces showed light spalling signatures. The propeller electric motor assembly was attached to an electrical source and operated normally. Figure 2. Operation and Service Instructions, 215 Propeller excerpt. Review of the airplane’s maintenance records revealed that the propeller overhaul had been completed on September 15, 2021, about 252 flight hours before the accident. The last inspections on the airplane, engine, and propeller had been completed on December 1, 2022, about 95 flight hours before the accident. No additional records documenting the overhaul were available for review, and the personnel who completed the overhaul could not be reached for interview. ## Aircraft - Registration: [N620D](https://openairdocs.org/aircraft/N620D), registered now, S/N D-2879, built 1951 (OpenAirDocs) - Reported make and model: BEECH C35 - Registry model: [Beech C35](https://openairdocs.org/model/beech-c35) (registry code 1151508) (OpenAirDocs) - Registry engine: [Continental E185 series](https://openairdocs.org/engine/continental-e185-series) (registry code 17014, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-2879 - Year built: 1951 - Airframe hours: 3274.52 - Engines: Continental Motors E-225-8 225 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Rubin Kenneth - Airworthiness certificate: Standard, Normal - Last inspection: Annual, December 17, 2022, 95 hours before - Departed: KVGT, Las Vegas, NV - Destination: KRKS, Rock Springs, WY - Flight plan: IFR - Airport: RKS, Southwest Wyoming Regional Airport, runway 3, 5,228 × 75 ft, asphalt - Equipment: ADS-B, Electronic flight bag or handheld device, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 52; injuries: minor; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review January 21, 2023; seat: left; restraint: 3-point; flight hours: 554 total, 155 in this make and model, 496 as pilot in command, 34 in the last 90 days, 1 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 350° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: 16,764 ft overcast - Temperature: 20 °F, dew point 9 °F - Altimeter: 30.42 inHg - Observed at: KRKS, 0.5 nm away ## 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 20230720018569A](https://openairdocs.org/incident/20230720018569A), Jul 20, 2023: Beech C35, Rock Springs, WY, Substantial damage. During climb, the pilot and Passenger heard a “pop sound” from the engine compartment. The passenger thought he saw something “Fly up from the engine” and was… ## Docket (16 files) The files NTSB released with the investigation on June 4, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192689. 80.8 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15932673&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - First responder statement-airport director (item 2, PDF, 1 page, 86 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18688614&FileExtension=pdf&FileName=Airport%20Director-Witness%20Statement-Rel.pdf - Photo array-onsite (courtesy of the airport manager) (item 3, PDF, 5 pages, 4 photos, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18688734&FileExtension=pdf&FileName=Onsite%20Photo%20Array-Courtesy%20of%20the%20Airport%20Manager-Rel.pdf - Maintenance records (item 4, PDF, 6 pages, 46.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689618&FileExtension=pdf&FileName=Last%20Annual%20Inspections_Redacted-Rel.pdf - Beech 215 propeller-operating and maintenance tips (item 5, PDF, 3 pages, 328 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689194&FileExtension=pdf&FileName=Beechcraft%20Propeller-Rel.pdf - Beech 215 propeller-description and image breakdown (item 6, PDF, 1 page, 486 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689075&FileExtension=pdf&FileName=Overhaul%20Manual%20Description%20and%20Image-Rel.pdf - Google earth image-airport and accident site (item 7, PDF, 1 page, 21.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689877&FileExtension=pdf&FileName=GE%20View%20Accident%20Site-Rel.pdf - NTSB wreckage examination summary report (item 8, PDF, 8 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689085&FileExtension=pdf&FileName=WPR23LA283%20Wreckage%20Examination%20Summary-Rel.pdf - NTSB propeller examination summary report (item 9, PDF, 9 pages, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689054&FileExtension=pdf&FileName=WPR23LA283%20Propeller%20Examination%20Factual%20Summary-Rel.pdf - Jpi raw excel data (item 10, PDF, 24 pages, 96 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689204&FileExtension=pdf&FileName=JPI%20Data%20Graphs-Rel.pdf - Jpi data graphs (item 11, PDF, 4 pages, 96 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18688229&FileExtension=pdf&FileName=JPI%20Data%20Graphs-Rel.pdf - Email-jpi data download information (item 12, PDF, 2 pages, 213 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18688724&FileExtension=pdf&FileName=ES%20Email-RE_%20192698%20WPR23LA283-Instrument%20Downloads_Redacted-Rel.pdf - NTSB final narrative party review-faa (item 13, PDF, 2 pages, 165 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18697946&FileExtension=pdf&FileName=RE_%20WPR23LA283%20Final%20Narrative-Party%20Review-FAA_Redacted-Rel.pdf - NTSB final narrative party review-textron aviation (item 14, PDF, 2 pages, 164 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18710907&FileExtension=pdf&FileName=RE_%20WPR23LA283%20Final%20Narrative-Party%20Review-TA_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation-textron aviation (item 15, PDF, 9 pages, 4.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18689044&FileExtension=pdf&FileName=Party%20Form%20TA_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 16, PDF, 1 page, 187 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18688624&FileExtension=pdf&FileName=NTSB%20Wreckage%20Release%20Form_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.