# NTSB CEN20LA294: Rockwell S2R, N1662S, Harlan, IA, July 20, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: July 20, 2020, 16:00 local (21:00 UTC) - Place: Harlan, IA - Coordinates: 41.650791, -95.319587 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=41.6508&lon=-95.3196&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Federal Aviation Administration; Des Moines FSDO - ADs cited in the narratives: [AD 79-10-10](https://openairdocs.org/ad/79-10-10) (OpenAirDocs) - NTSB case key (mKey): 101640 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA294 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101640/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101640 - Page: https://openairdocs.org/ntsb/CEN20LA294 ## Probable cause The fatigue fracture of the upper rudder hinge that resulted in a partial separation of the rudder from the airplane during a spray pass. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Empennage structure: rudder](https://openairdocs.org/ntsb-findings/01035540): Aircraft › Aircraft structures · Fatigue/wear/corrosion (probable cause); cases with it: [Aero Commander S2R, 1 case](https://openairdocs.org/ntsb-findings/01035540/cases.md?model=0143022), [All aircraft, 15 cases](https://openairdocs.org/ntsb-findings/01035540/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Aero Commander S2R, 1 case](https://openairdocs.org/ntsb-events/040/sequence.md?model=0143022), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Maneuvering-low-alt flying: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Aero Commander S2R, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=0143022), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) ## Analysis The pilot of the aerial application flight was spraying a field when the top portion of the rudder partially separated from the airplane. The airplane yawed abruptly left and remained in an uncontrollable left yaw for about 10 to 15 minutes, at times pitching uncontrollably downward until the broken portion of the rudder separated. The airplane landed without further incident. Postaccident metallurgical examination of the upper rudder hinge revealed a fatigue fracture. ## Factual narrative On July 20, 2020, at 1600 central daylight time, an Aero Commander S2-R, N1662S, was substantially damaged when it was involved in an accident near Harlan, Iowa. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot stated that, during a spray pass, he felt the airplane yaw abruptly left and remain in an uncontrollable left yaw for about 10 to 15 minutes, at times pitching uncontrollably downward. The top 2/3 of the rudder had separated and the remainder was attached. When the top portion of the rudder completely separated, the pilot regained control of the airplane and landed without further incident. The separated portion of the rudder was not recovered. The top rudder hinge had fractured through and had brown-colored features consistent with corrosion. The remaining portion of the rudder and stabilizer was retained for metallurgical examination. Postaccident metallurgical examination revealed the upper rudder hinge was fractured through the two hinge barrels attached to the vertical stabilizer aft spar. The interior surfaces of the barrels were mostly covered with a tacky black grease. Thick grease deposits were also present on adjacent surfaces above the upper barrel and below the lower barrel. Portions of the upper hinge barrel interior fracture surfaces had flat fracture features in the radial plane with curving boundaries, features consistent with fatigue. Ratchet marks were also observed consistent with fatigue emanating from multiple origins. The fatigue regions covered approximately 90% of the fractured cross-section. The vertical stabilizer was cleaned, inspected, and repaired March 8, 2011, in accordance with designated engineering approved data. Airworthiness Directive 79-10-10, To Prevent Separation of the Single Upper Hinge from The Rudder Assembly, was complied with June 3, 1997, per Federal Aviation Administration Form 337 by installing an additional rudder hinge. ## Aircraft - Registration: [N1662S](https://openairdocs.org/aircraft/N1662S), registered now, S/N 1835R, built 1973 (OpenAirDocs) - Reported make and model: Rockwell S2R (No Series) - Registry model: [Aero Commander S2R](https://openairdocs.org/model/aero-commander-s2r) (registry code 0143022) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1835R - Year built: 1973 - Airframe hours: 11955 - Engines: Honeywell TPE331-10 940 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Slater's Spray Service - Registered owner: Individual - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, July 11, 2020 - Departed: HNR, Harland, IA - Destination: HNR, Harland, IA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 29; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review March 25, 2019; seat: center; restraint: 3-point; flight hours: 5,533 total, 1,160 in this make and model, 5,486 as pilot in command, 230 in the last 90 days, 226 in the last 30 days, 13 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 6 knots - Lowest ceiling: 3,900 ft broken - Temperature: 77 °F, dew point 63 °F - Altimeter: 30.01 inHg - Observed at: HNR ## 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 20200720010609A](https://openairdocs.org/incident/20200720010609A), Jul 20, 2020: Aero Commander S2R, Harlan, IA, Minor damage. Pilot was on a spray run when the aircraft started yawing to the left and pitching down. The pilot had both hands on the stick pulling back to keep from… ## Docket (6 files) The files NTSB released with the investigation on March 2, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101640. 9.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 7 pages, 4.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11611024&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Record of correspondence FAA (item 2, PDF, 1 page, 47 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11614551&FileExtension=pdf&FileName=RECORD%20OF%20CORRESPONDENCE%20FAA-Rel.pdf - Materials laboratory factual report 20-058 (item 3, PDF, 7 pages, 15 photos, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11596836&FileExtension=pdf&FileName=20-058-Rel.pdf - AD 79-10-10 (item 4, PDF, 3 pages, 415 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11612242&FileExtension=pdf&FileName=AD-Rel.pdf - SB-AG-15 (item 5, PDF, 4 pages, 276 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11613396&FileExtension=pdf&FileName=sb-ag-15-rev-1-Rel.pdf.pdf - Photo log (item 6, PDF, 4 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11614015&FileExtension=pdf&FileName=Photo%20Log-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.