# NTSB CEN20LA187: Bell OH-58A, N153SA, West Branch, MI, May 20, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 20, 2020, 09:33 local (13:33 UTC) - Place: West Branch, MI - Coordinates: 44.215557, -84.188056 - Nearby events: https://openairdocs.org/map.md?lat=44.2156&lon=-84.1881&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Defining event: [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA Flight Standards Disrrict Office - NTSB case key (mKey): 101315 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA187 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101315/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101315 - Page: https://openairdocs.org/ntsb/CEN20LA187 ## Probable cause The pilot's failure to maintain rotor rpm during a precautionary autorotation, which resulted in a hard landing. Contributing to the accident was the airframe vibration for reasons that could not be determined because examination of the helicopter revealed no anomalies. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Bell OH-58A, 3 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=1181579), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Bell OH-58A, 8 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=1181579), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Bell OH-58A, 1 case](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=1181579), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Unknown or undetermined](https://openairdocs.org/ntsb-events/000); cases with it: [Bell OH-58A, 2 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=1181579), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) - [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092) (defining event); cases with it: [Bell OH-58A, 10 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=1181579), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis While cruising about 500 feet above ground level, the pilot of the helicopter felt a vibration and entered a precautionary autorotation, though he did not observe any caution or warning lights or horns associated with the vibration. The pilot turned toward an open field for landing and, after clearing some trees, the low rotor rpm horn activated. He reduced collective and made a hard run-on landing, during which the helicopter slid about 20 to 30 ft on its skids before coming to rest upright. The main rotor drooped and one blade struck the tail boom, severing the tail rotor drive shaft and resulting in substantial damage. There was also crush damage to the underside of the tail boom caused by impact forces. The pilot could not describe the location or frequency of the vibration, and the passenger reported that he felt no vibration. Postaccident and follow-up inspections of the helicopter by revealed no anomalies that would have resulted in the vibration. Although the source of the vibration could not be determined, it is likely that the hard landing was the result of the pilot's failure to maintain rotor rpm during the precautionary autorotation. ## Factual narrative On May 20, 2020, about 0933 eastern daylight time, an experimental exhibition category Bell OH-58A helicopter, N153SA, was substantially damaged when it was involved in an accident near West Bank, Michigan. The commercial pilot and passenger were not injured. The helicopter was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight. The pilot told Federal Aviation Administration (FAA) inspectors that he and his passenger departed Peach Lake Heliport (89MI), his private heliport for a local flight to Midland, Michigan, to observe recent flood damage. During the return flight, at an altitude of about 500 ft above ground level, the pilot felt an airframe vibration, and he immediately entered a precautionary autorotation. He did not observe any caution or warning lights or horns associated with the vibration. The pilot made a 200° left turn to an open field, and after the helicopter cleared some trees during the approach, the low rotor rpm horn activated. The pilot reduced collective and made a hard run-on landing. The helicopter slid about 20 to 30 ft on its skids before it came to rest upright. The main rotor drooped, and one blade struck the tail boom, severing the tail rotor drive shaft; the underside of the tail boom also sustained impact damage. The pilot could not describe to Federal Aviation Administration inspectors the location or frequency of the vibration, and the passenger reported that he felt no vibration. Postaccident and follow-up inspections by the pilot's mechanic found no evidence of the source of the vibration. ## Aircraft - Registration: [N153SA](https://openairdocs.org/aircraft/N153SA), registered now, S/N 68-16711, built 1968 (OpenAirDocs) - Reported make and model: Bell OH-58A - Registry model: [Bell OH-58A](https://openairdocs.org/model/bell-oh-58a) (registry code 1181579) (OpenAirDocs) - Registry engine: [Allison 250-C10D](https://openairdocs.org/engine/allison-250-c10d) (registry code 03035, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 68-16711 - Year built: 1968 - Engines: Allison 250-C10D 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Departed: 89MI, West Branch, MI - Destination: 89MI, West Branch, MI ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 69; injuries: none; commercial, private; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane; medical: basicmed; seat: right; restraint: 3-point; flight hours: 3,900 total, 100 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 90° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F, dew point 41 °F - Altimeter: 30.27 inHg - Observed at: Y31, 3,135 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 20200520006899A](https://openairdocs.org/incident/20200520006899A), May 20, 2020: Bell OH-58A, West Branch, MI, Substantial damage. On may 20, 2020 at 0933 local time, a Bell helicopter, inc. OH-58A aircraft, N153SA, registered to and operated by a commercial rated pilot, received… ## Docket (3 files) The files NTSB released with the investigation on February 16, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101315. 1.5 MB in all. - FAA inspector's statement (item 1, PDF, 1 page, 63 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=9761906&FileExtension=pdf&FileName=FAA%20Inspector%27s%20Statement-Rel.pdf - Memorandum re michael w. matthews (item 2, PDF, 1 page, 131 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=9885676&FileExtension=pdf&FileName=2-Memorandum%20Re%20Michael%20W.%20Matthews-Rel.pdf - Accident report photographs (item 3, PDF, 7 pages, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=9899670&FileExtension=pdf&FileName=3-Accident%20Report%20Photographs-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.