# NTSB WPR17LA051: Cessna 421C, N71RC, Jackson, CA, January 7, 2017

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: January 6, 2017, 17:20 local (Jan 7, 2017, 01:20 UTC)
- Place: Jackson, CA
- Coordinates: 38.376945, -120.794166 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=38.3769&lon=-120.7942&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Defining event: [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report November 19, 2019
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: FAA Sacramento FSDO, Federal Aviation Administration, Textron Aviatioin
- SAIBs cited in the narratives: [SAIB CE-14-19](https://openairdocs.org/saib/CE-14-19) (OpenAirDocs)
- NTSB case key (mKey): 94575
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR17LA051
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/94575/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=94575
- Page: https://openairdocs.org/ntsb/WPR17LA051

## Probable cause

The failure of the right main landing gear torque link bolt in overstress, which resulted in the collapse of the landing gear during the landing roll.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=2076016), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md)
- [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Capability exceeded (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=2076016), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Cessna 421C, 7 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=2076016), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md)
- [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Cessna 421C, 9 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=2076016), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md)
- [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 421C, 15 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2076016), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The airline transport pilot reported that, during the landing roll at the end of a cross-country flight, when he attempted to lightly apply the brakes, the airplane began to yaw from side to side. The airplane subsequently exited the right side of the runway and sustained substantial damage to the right wing spar. During the landing, the right main landing gear collapsed. An on-site examination revealed that the right main landing gear torque link assembly had separated at the hinge attach point due to the failure of the torque link bolt. Although the bolt was located at the accident site, the bolt's nut, cotter pin, and washer were missing. Further examination revealed that the torque link bolt threads had been rounded over and exhibited remnants of material consistent with the threads of the mating nut. In addition, remnants of the cotter pin that was installed through the bolt hole were visible. The sheared cotter pin and threads from the nut that remained within the bolt threads suggest that the torque link bolt/nut assembly was overloaded, which resulted in the landing gear collapse. A Federal Aviation Administration special airworthiness information bulletin had been issued about 3 years before the accident to advise owners, operators, and maintenance technicians of the make and model airplane of the need to inspect the main landing gear torque link assembly to ensure the correct thickness of washers and to ensure that the washers are installed properly, and a Cessna service bulletin had also been issued previously regarding the washers. However, no maintenance records were available to determine the airplane's maintenance history or compliance with the applicable bulletins.

## Factual narrative

On January 6, 2017, about 1720 Pacific standard time, a Cessna 421C airplane, N71RC, sustained substantial damage to the right wing spar following the collapse of the right main landing gear during the landing roll at Westover Field/Amador County Airport, Jackson, California. The airline transport rated pilot was not injured. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed, and no flight plan was filed for the cross country flight. The flight originated from the Palo Alto Airport, Palo Alto, California about 1640. The pilot stated that he flew a normal left-hand traffic pattern for runway 19. The flare and initial touchdown were normal, however, immediately after the initial touchdown, something did not feel right. When he attempted to lightly apply the brakes the airplane began to yaw from one side to the other. He released the brakes and attempted to slow the airplane with reverse thrust, but the airplane exited the paved runway surface and came to a stop in the grass and dirt area about 20 ft off the right side of the runway. During the landing the right main landing gear collapsed. An onsite examination of the airplane revealed that the right main landing gear torque link assembly had separated at the hinge attach point due to the failure of the torque link bolt. The bolt's nut, cotter pin and washer were not located during the investigation. The subject bolt was subsequently shipped to the National Transportation Safety Board's Materials Laboratory in Washington, D.C. for examination. As a result of the examination, the report revealed that the torque link bolt threads had been rounded over and exhibited remnants of material consistent with the threads of the mating nut. Further, remains of a cotter pin that was installed through the bolt hole were also visible. The report concluded that the deformation of the cotter pin remains was indicative of a shear overstress fracture. (Refer to the NTSB Materials Laboratory Factual Report No. 18-062, which is appended to the docket for this report.) It was revealed during the investigation that Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin (SAIB) CE-14-19, dated May 30, 2014, titled "Landing Gear; Main Landing Gear (MLG) Torque Link," was published to advise owners, operators, and maintenance technicians of Cessna 300 and 400 Models and Series of an airworthiness concerns, specifically the need to inspect the MLG torque link assembly to ensure the correct thickness washers are installed, and to ensure the washers are installed properly. The SAIB was preceded by Cessna Service Bulletin ME83-37, dated November 23, 1983, "Main Landing Gear Scissor Washer Replacement which recommended replacement of the two outer washers on the main landing gear scissor link for Cessna Model 421s, and Cessna Service Bulletin MEB02-12, which specified replacement of theoriginal washers at each end of hinge point attachment stack-up for Cessna Model 310s. (Refer to FAA SAIB CE-14-9, and Cessna Service Bulletin ME83-37, both of which are appended to the docket for this report.) Except for the right main landing gear torque link bolt, no other components of the right main landing gear assembly were accounted for during the investigation. Additionally, no maintenance records were recovered during the investigation for review to determine compliance with the SAIB's. The pilot did not submit a Pilot/Operator Aircraft Accident/Incident Report (NTSB) Form 6120.1.

## Aircraft

- Registration: [N71RC](https://openairdocs.org/deregistered/N71RC-2017-04-13), registration cancelled 2017-04-13, S/N 421C0423, built 1977 (OpenAirDocs)
- Reported make and model: CESSNA 421C (C)
- Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs)
- Registry engine: [Lycoming LTP-101-600](https://openairdocs.org/engine/lycoming-ltp-101-600) (registry code 41565, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 421C0423
- Year built: 1977
- Airframe hours: 2929.1
- Engines: Lycoming LTP 101-600 600 horsepower turbo prop; Lycoming LTP 101-600 600 horsepower turbo prop
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, August 11, 2016, 11 hours before
- Departed: PAO, Palo Alto, CA
- Destination: JAQ, Jackson, CA
- Flight plan: Unknown
- Airport: JAQ, Westover Field Amador County, runway 19, 3,401 × 60 ft, asphalt
- Equipment: Unknown

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 58; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review September 4, 2016; seat: left; restraint: 4-point; flight hours: 1,802 total, 62 in this make and model

## Weather

- Conditions: Visual (VMC), Dusk
- Wind: 10° at 4 knots
- Visibility: 10 statute miles
- Lowest ceiling: 25,000 ft broken
- Temperature: 39 °F, dew point 36 °F
- Altimeter: 30.10 inHg
- Observed at: KSMF, 42 nm away

## Docket (7 files)

The files NTSB released with the investigation on September 9, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=94575. 1.2 MB in all.

- NTSB Materials Laboratory Factual Report (item 1, .PDF, 208 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475682&FileExtension=.PDF&FileName=NTSB%20Materials%20Laboratory%20Factual%20Report-Master.PDF
- NTSB IIC's Initial Investigation Notes (item 2, .PDF, 428 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475683&FileExtension=.PDF&FileName=NTSB%20IIC%27s%20Initial%20Investigation%20Notes-Master.PDF
- Cessna Service Bulletin MEB02-12 - Main Landing Gear Torque Link Inspection (item 3, .PDF, 218 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475684&FileExtension=.PDF&FileName=Cessna%20Service%20Bulletin%20MEB02-12%20-%20Main%20Landing%20Gear%20Torque%20Link%20Inspection-Master.PDF
- Cessna Service Information Letter ME83-37 (Main Landing Gear Scissor Washer Replacemrnt) (item 4, .PDF, 92 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475685&FileExtension=.PDF&FileName=Cessna%20Service%20Information%20Letter%20ME83-37%20(Main%20Landing%20Gear%20Scissor%20Washer%20Replacemrnt)-Master.PDF
- FAA Special Airworthiness Information Bulletin CE-14-19 - Landing Gear; Main Landing Gear (MLG) Torque Link (item 5, .PDF, 148 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475686&FileExtension=.PDF&FileName=FAA%20Special%20Airworthiness%20Information%20Bulletin%20CE-14-19%20-%20Landing%20Gear;%20Main%20Landing%20Gear%20(MLG)%20Torque%20Link-Master.PDF
- Textron Permission to use Proprietary Documents (item 6, .PDF, 71 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475687&FileExtension=.PDF&FileName=Textron%20Permission%20to%20use%20Proprietary%20Documents-Master.PDF
- Statement of Party Representatives to NTSB Investigation (item 7, .PDF, 72 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40475688&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.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.

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