# NTSB ERA21LA023: Bell 206, N777CP, Zephyrhills, FL, October 16, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: October 16, 2020, 15:15 local (19:15 UTC) - Place: Zephyrhills, FL - Coordinates: 28.338616, -81.957469 - Nearby events: https://openairdocs.org/map.md?lat=28.3386&lon=-81.9575&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO, Rolls Royce - NTSB case key (mKey): 102161 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA21LA023 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102161/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102161 - Page: https://openairdocs.org/ntsb/ERA21LA023 ## Probable cause Improper torquing of the “B” nut at the fuel control unit, which led to a total loss of engine power and subsequent autorotation that resulted in substantial damage. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control: fuel controlling system](https://openairdocs.org/ntsb-findings/01057320): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Bell 206B, 2 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md?model=1181511), [All aircraft, 59 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Bell 206B, 4 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=1181511), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Bell 206B, 17 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1181511), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) ## Analysis While in cruise flight, the pilot heard a binding sound and felt a reduction in engine power. The low rotor rpm aural alarm then sounded, and he initiated an autorotation to swampy terrain. The helicopter came to rest amongst pine trees and undergrowth. The tailboom was impact separated and the main rotors were fractured about midspan. During a detailed examination of the helicopter, the “B” nut at the engine fuel control unit was found loose with no thread engagement. During a test run of the engine, the “B” nut was tightened and torqued to proper specification. The engine ran smoothly and continuously at all power settings. A review of the helicopter’s maintenance records revealed the last annual inspection was completed about 75 hours prior to the accident. The pilot, who also holds an airframe and powerplant certificate, was the last person to perform maintenance on the engine. According to the Rolls-Royce maintenance manual, torque paint must be applied to all the rigid tube “B” nuts to ensure proper tightening. According to the maintenance manual, “failure to properly install, align, and tighten fuel, oil, and air fittings could result in an engine failure.” ## Factual narrative On October 16, 2020, about 1515 eastern daylight time, a Bell 206B, N777CP, was substantially damaged when it was involved in an accident near Zephyrhills, Florida. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, about 15 minutes after departure, he heard a “binding sound” and felt a reduction in engine power and a slight nose left yaw. He checked his engine instruments and noted no illumination of annunciator lights or engine warnings. The low rotor rpm aural alarm then sounded, and he initiated an autorotation to swampy terrain. According to the Federal Aviation Administration inspector who responded to the accident site, the helicopter came to rest among pine trees and undergrowth. The tailboom was impact separated, and the main rotors were fractured about midspan. A detailed examination revealed the “B” nut at the engine fuel control unit was loose with no thread engagement. The nut was also missing the torque stripe markings on the line as required by the Rolls-Royce maintenance manual. During a test run of the engine, the “B” nut was tightened and torqued to proper specification. The engine ran smoothly and continuously at all power settings. A review of the helicopter’s maintenance records revealed the last annual inspection was completed about 75 hours prior to the accident. At that time, the Nos. 1 and 2 turbine wheels were replaced. The pilot also holds an airframe and powerplant certificate and was the last person to perform maintenance on the engine. According to the Rolls-Royce maintenance manual, torque paint must be applied to all the rigid tube “B” nuts and reapplied each time the nut is loosened and tightened. The manual states that “Proper tightening of the engine tubing connections is critical to flight safety. Failure to properly install, align, and tighten fuel, oil, and air fittings cold result in an engine failure.” ## Aircraft - Registration: [N777CP](https://openairdocs.org/aircraft/N777CP), registered now, S/N 3429 (OpenAirDocs) - Reported make and model: BELL 206 (B) - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Allison 250 SER 250HP](https://openairdocs.org/engine/allison-250-ser-250hp) (registry code 03002, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 3429 - Year built: 1981 - Airframe hours: 12582 - Engines: Rolls Royce 250 C20-B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 8, 2020, 74.2 hours before - Departed: Plant City, FL - Destination: KCRG, Jacksonville, FL - Flight plan: Company VFR - Equipment: Onboard weather, Handheld GPS, Electronic flight bag or handheld device, ADS-B, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 2, without waivers/limitations; last flight review November 23, 2018; seat: front; restraint: lap only; flight hours: 6,860 total, 2,400 in this make and model, 6,600 as pilot in command, 80 in the last 90 days, 30 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 10° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 68 °F - Altimeter: 29.98 inHg - Observed at: ZPH, 12 nm away - METAR: KZPH 161915Z AUTO 01009KT 10SM CLR 31/20 A2998 RMK A02 T03060196 ## 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 20201016015159A](https://openairdocs.org/incident/20201016015159A), Oct 16, 2020: Bell 206B, Lakeland, FL, Substantial damage. Aircraft departed from private residence in plant city FL at aprox 1500 hrs EST. In route to kcrg craig field jax, approximately 20 minutes into flight, at… ## Docket (9 files) The files NTSB released with the investigation on June 10, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102161. 12.2 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 922 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11530284&FileExtension=pdf&FileName=NTSB%20Accident%20Report_Redacted-Rel.pdf - Record of conversation - pilot (item 2, PDF, 2 pages, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12073227&FileExtension=pdf&FileName=ROC-%20Pilot-Rel.pdf - FAA inspector's statement (item 3, PDF, 1 page, 432 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12072242&FileExtension=pdf&FileName=ASI%20James%20Boles%20FAA%20FSDO%20SO15%20IIC%20Statement%20of%20Accident%20Investigation_Redacted-Rel.pdf - Maintenance records (item 4, PDF, 4 pages, 4.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12072166&FileExtension=pdf&FileName=Maintenance%20records_Redacted-Rel.pdf - Rolls-royce maintenance manual (excerpts) (item 5, PDF, 5 pages, 239 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12112402&FileExtension=pdf&FileName=Rolls-Royce%20maintenance%20manual%20excerpts-Rel.pdf - Photos (item 6, PDF, 4 pages, 4.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12072488&FileExtension=pdf&FileName=Photos-Rel.pdf - Excerpt from rolls-royce engine examination report (item 7, PDF, 5 pages, 93 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12072366&FileExtension=pdf&FileName=Excerpt%20from%20Rolls-Royce%20Engine%20Report-Rel.pdf - Statement of party representatives to NTSB investigation (item 8, PDF, 14 pages, 493 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12072694&FileExtension=pdf&FileName=RR%20NTSB%20Party%20Form_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 9, PDF, 1 page, 573 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12079856&FileExtension=pdf&FileName=N777CP%20Wreckage%20Release_Redacted-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.