# NTSB WPR20LA025: North American SNJ-4, N694US, Heber City, UT, November 16, 2019 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: November 16, 2019, 14:30 local (21:30 UTC) - Place: Heber City, UT - Coordinates: 40.478889, -111.433891 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.4789&lon=-111.4339&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 100578 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR20LA025 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100578/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100578 - Page: https://openairdocs.org/ntsb/WPR20LA025 ## Probable cause The pilot’s loss of directional control during landing as a result of the separated tailwheel-to-rudder link rod ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: steering unit](https://openairdocs.org/ntsb-findings/01023251): Aircraft › Aircraft systems · Damaged/degraded (probable cause); cases with it: [North American SNJ-4, 1 case](https://openairdocs.org/ntsb-findings/01023251/cases.md?model=6400414), [All aircraft, 4 cases](https://openairdocs.org/ntsb-findings/01023251/cases.md) - [Performance/control parameters: directional control](https://openairdocs.org/ntsb-findings/01062020): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [North American SNJ-4, 2 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=6400414), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Misc hardware: fasteners](https://openairdocs.org/ntsb-findings/01071430): Aircraft › Fluids/misc hardware · Unknown/Not determined (probable cause); cases with it: [North American SNJ-4, 1 case](https://openairdocs.org/ntsb-findings/01071430/cases.md?model=6400414), [All aircraft, 58 cases](https://openairdocs.org/ntsb-findings/01071430/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: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [North American SNJ-4, 3 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=6400414), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [North American SNJ-4, 3 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=6400414), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The pilot reported that after an uneventful three-point landing in the tailwheel equipped airplane with an 8-knot crosswind, the airplane veered to the left. Despite the pilot's control inputs, the airplane exited the left side of the runway, resulting in substantial damage to the right wing. Postaccident examination of the airplane revealed that the tailwheel-to-rudder link rod was separated from the rudder control horn. The associated attachment hardware, which included a bolt, castellated nut, and cotter pin were not located. Elongation and inward bending were observed on the upper and lower bearing shields, which most likely was a result of the bolt separating from the assembly. It could not be determined if the link rod bolt had a cotter pin installed prior to the accident. Although separation of the tailwheel-to-rudder link rod would disable tailwheel steering, which could reduce ability to maintain directional control during landing, the effect can be counteracted by other control inputs and differential braking. ## Factual narrative On November 16, 2019, about 1430 mountain standard time, a North American SNJ-4, N694US, was substantially damaged when it was involved in an accident at Heber Valley Airport (HCR), Heber City, Utah. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that prior to entering the airport traffic pattern, he listened to the airport’s automated weather observing system, noting the wind was from 340° at 9 knots, which equates to an 8-knot crosswind component. The pilot entered the airport traffic pattern for runway 4 and conducted an uneventful three-point landing in the tailwheel-equipped airplane. About 500 to 700 ft. after touchdown, the airplane veered to the left and despite the pilot's control inputs, exited the left side of the runway. Subsequently, the right main landing gear separated, and the airplane came to rest upright. Examination of the airplane by the pilot revealed that the right wing was structurally damaged. The tailwheel-to-rudder link rod, which provides tailwheel steering, was found separated from the rudder control horn, as seen in figure 1. The associated attachment hardware, which included a bolt, castellated nut, and cotter pin, were not located. Figure 1: Excerpt from a video provided by the pilot, showing the tailwheel to rudder link rod and damage. The rudder control horn side ball bearing was damaged, and upper and lower bearing housing shields were elongated and exhibited an inward bend along a portion of both shields, about 180° opposite of one another. The inner race was intact. The bearing balls were mostly separated from the bearing assembly. The airplane was equipped with a steerable tailwheel that could be locked into place. With the tailwheel locked, steering to the left and right is limited to 15°. A tailwheel-to-rudder link rod attached the rudder control horn to the tailwheel control horn and each connection point incorporated installation of one AN4-12 bolt, two AN960-C416L washers, one AN310-4 nut, and one AN380-2-2 cotter pin. ## Aircraft - Registration: [N694US](https://openairdocs.org/aircraft/N694US), registered now, S/N 88-13627 (OpenAirDocs) - Reported make and model: North American SNJ-4 - Registry model: [North American SNJ-4](https://openairdocs.org/model/north-american-snj-4) (registry code 6400414) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 88-13627 - Engines: Pratt & Whitney R1340 600 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Wasatch Flyers LLC - Registered owner: Wasatch Flyers LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 1, 2019, 26.5 hours before - Departed: HCR, Heber City, UT - Destination: HCR, Heber City, UT - Airport: HCR, Heber Valley, runway 04, 6,898 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 70; injuries: none; commercial, airline transport; airplane ratings: single-engine sea, multi-engine sea; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review October 3, 2019; seat: front; restraint: 5-point; flight hours: 25,000 total, 30 in this make and model, 20,000 as pilot in command, 10 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 12 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 54 °F, dew point 21 °F - Altimeter: 30.20 inHg - Observed at: KHCR ## Docket (4 files) The files NTSB released with the investigation on May 25, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100578. 4.3 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11940889&FileExtension=pdf&FileName=6120%20t6_Redacted-Rel.pdf - Record of conversation - pilot (item 2, PDF, 1 page, 143 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11941251&FileExtension=pdf&FileName=Record%20of%20Conversation%20pilot-Rel.pdf - Tailwheel to rudder link rod examination (item 3, PDF, 4 pages, 5 photos, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11941698&FileExtension=pdf&FileName=tailwheel%20to%20rudder%20linkrod%20exam-Rel.pdf - Photo (item 4, PDF, 1 page, 1 photo, 880 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11941562&FileExtension=pdf&FileName=photo%20array-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.