Beechcraft C35 N620D

Summary

On 20 July 2023 at about 18:55 local time, a Beechcraft C35 registered N620D was involved in an accident near Rock Springs, Wyoming, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

20 July 2023 at 18:55

Classification

Accident

Location

Rock Springs, Wyoming, United States

Nearest airport

Southwest Wyoming Regional Air (RKS)

Coordinates

41.6007, -109.0512

Aircraft

Beechcraft C35

Registration

N620D

Category

Airplane

Year built

1951

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Las Vegas → Rock Springs

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR23LA283

2 people had minor injuries.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.