# NTSB CEN21LA389: Robinson Helicopter R22 Beta, N827SH, Arnaudville, LA, August 27, 2021

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Class 3 · Limited · Final report
- Date: August 27, 2021, 08:00 local (13:00 UTC)
- Place: Arnaudville, LA
- Coordinates: 30.395296, -91.934586 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=30.3953&lon=-91.9346&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Defining event: [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA
- NTSB case key (mKey): 103773
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN21LA389
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103773/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103773
- Page: https://openairdocs.org/ntsb/CEN21LA389

## Probable cause

The loss of tail rotor drive due to a fatigue failure of the tail rotor gearbox output shaft, which resulted in a loss of control during landing.

## Findings

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

- [Tail rotor drive system: tail rotor drive shaft](https://openairdocs.org/ntsb-findings/01046510): Aircraft › Aircraft propeller/rotor · Fatigue/wear/corrosion (probable cause); cases with it: [Robinson Helicopter R22 BETA, 2 cases](https://openairdocs.org/ntsb-findings/01046510/cases.md?model=7640110), [All aircraft, 25 cases](https://openairdocs.org/ntsb-findings/01046510/cases.md)
- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Robinson Helicopter R22 BETA, 96 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=7640110), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)

## Sequence of events

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

- [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Robinson Helicopter R22 BETA, 6 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=7640110), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md)
- [Landing-flare/touchdown: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242); cases with it: [Robinson Helicopter R22 BETA, 10 cases](https://openairdocs.org/ntsb-events/242/sequence.md?model=7640110), [All aircraft, 100 cases](https://openairdocs.org/ntsb-events/242/sequence.md)

## Analysis

While attempting to land at a staging location for a planned aerial application flight, the helicopter began to rotate to the right. The pilot was unable to regain control. The helicopter skids impacted a dirt field, and the helicopter rolled over onto its right side. The helicopter sustained substantial damage to its main rotor blades and fuselage. Disassembly of the helicopter for recovery revealed the tail rotor output shaft was fractured into two pieces. Examination of the output shaft revealed the fracture occurred between the mating tapered roller bearing and the bevel gear. The bevel gear side surface displayed progressive crack arrest marks consistent with fatigue cracking. Due to smear damage on the other fracture, it could not be determined if the fatigue cracking was the result of unidirectional bending fatigue (one origin) or reverse bending fatigue (two origins). The tail rotor output shaft function is to drive the tail rotor blades. A failed tail rotor output shaft would result in the loss of drive to the tail rotor blades, which in turn would cause a loss of tail rotor thrust to counter main rotor torque and loss of yaw control.

## Factual narrative

On August 27, 2021, about 0800 central daylight time, a Robinson R22 Beta helicopter, N827SH, sustained substantial damage when it was involved in an accident near Arnaudville, Louisiana. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight. According to the pilot, while attempting to land at his staging location for a planned aerial application flight, the helicopter began to rotate to the right. The pilot was unable to regain control; the helicopter skids impact a dirt field, and the helicopter rolled over onto its right side. The helicopter sustained substantial damage to its main rotor blades and fuselage. While disassembling the helicopter for recovery, the tail rotor output shaft was found fractured into two pieces. The shaft was retained for further examination by the National Transportation Safety Board (NTSB) Materials Laboratory. According to Robinson Helicopters, the tail rotor gearbox contains a splash-lubricated spiral-bevel gear set. The function of the tail rotor output shaft is to drive the tail rotor blades. A failed tail rotor output shaft results in the loss of drive to the tail rotor blades, which in turn causes a loss of tail rotor thrust to counter main rotor torque and loss of yaw control. A review of the helicopter records revealed a serviceable tail rotor gearbox (serial number 3242) was installed on April 18, 2020, at a total helicopter time of 4,255.6 hours. The helicopter total time at the time of the accident was not reported. NTSB Material Laboratory examination of the output shaft revealed the fracture occurred between the mating tapered roller bearing and the bevel gear. Heavy smearing damage was observed on both fracture surfaces. The damage was likely secondary and due to contact of the fracture surfaces post-separation. The bevel gear side surface displayed progressive crack arrest marks consistent with fatigue cracking. Due to smear damage on the other fracture, it could not be determined if the fatigue cracking was the result of unidirectional bending fatigue (one origin) or reverse bending fatigue (two origins).

## Aircraft

- Registration: [N827SH](https://openairdocs.org/aircraft/N827SH), registered now, S/N 3780, built 2005 (OpenAirDocs)
- Reported make and model: ROBINSON HELICOPTER R22 BETA
- Registry model: [Robinson Helicopter R22 BETA](https://openairdocs.org/model/robinson-helicopter-r22-beta) (registry code 7640110) (OpenAirDocs)
- Registry engine: [Lycoming O-360-J2A](https://openairdocs.org/engine/lycoming-o-360-j2a) (registry code 42314, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 3780
- Year built: 2005
- Airframe hours: 4301
- Engines: Lycoming O-360-J2A 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Positioning, Part 91
- Operator: 1 Acadiana Helicopters Company LLC
- Registered owner: 1 Acadiana Helicopters Company LLC
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, January 10, 2021
- Departed: New Iberia, LA
- Destination: Same as departure
- Equipment: None

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 63; injuries: minor; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter; medical: class 2, without waivers/limitations; last flight review June 25, 2020; seat: right; restraint: 3-point; flight hours: 19,000 total, 10,000 in this make and model, 18,000 as pilot in command, 10 in the last 90 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 40° at 3 knots
- Visibility: 7 statute miles
- Lowest ceiling: none
- Temperature: 73 °F, dew point 72 °F
- Altimeter: 29.96 inHg
- Observed at: KLFT, 12 nm away
- METAR: KLFT 271153Z 04003KT 7SM CLR 23/22 A2996 RMK AO2 SLP145 T02330222 10244 20233 55002

## 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 20210827013099A](https://openairdocs.org/incident/20210827013099A), Aug 27, 2021: Robinson Helicopter R22 BETA, Arnaudville, LA, Substantial damage. Pilot stated after landing he picked up to reposition the aircraft. At about 5 feet the aircraft started spinning to the right and he lost control and rolled…

## Docket (4 files)

The files NTSB released with the investigation on December 29, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103773. 13.6 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 6.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14191321&FileExtension=pdf&FileName=Pilot%206120_Redacted-Rel.pdf
- Excerpt of helicopter records (item 2, PDF, 2 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14191436&FileExtension=pdf&FileName=Aircraft%20Records_Redacted-Rel.pdf
- NTSB materials laboratory report (item 3, PDF, 9 pages, 4.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14191754&FileExtension=pdf&FileName=22-043%20Materials%20Laboratory%20Factual%20Report%20(CEN21LA389)-Rel.pdf
- Accident photographs (item 4, PDF, 2 pages, 932 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14910076&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.

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