# NTSB ANC03LA073: Bell 206B, N111MT, Aniak, AK, July 10, 2003 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: July 9, 2003, 18:00 local (Jul 10, 2003, 02:00 UTC) - Place: Aniak, AK - Coordinates: 61.581665, -159.54306 - Nearby events: https://openairdocs.org/map.md?lat=61.5817&lon=-159.5431&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report March 30, 2004 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Anchorage FSDO-03 - NTSB case key (mKey): 57465 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC03LA073 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/57465/pdf - Page: https://openairdocs.org/ntsb/ANC03LA073 ## Probable cause The compressor discharge pressure line (Pc line) B-nut coming loose at the fuel control unit, which resulted in a total loss of engine power, and subsequent in-flight collision with trees during an autorotation. A factor associated with the accident was the improper installation of the Pc line B-nut by company maintenance personnel. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, cruise - normal - fuel system,pc line - loose (cause) - maintenance,installation - improper, company maintenance personnel (contributing factor) - Forced landing, emergency descent/landing - autorotation - performed, pilot in command - In flight collision with object, descent - emergency - object - tree(s) ## Analysis The helicopter was operating as a Title 14, CFR Part 91, positioning flight in visual meteorological conditions when it had a total loss of engine power while in cruise flight. The pilot said the first indication of a problem was the illumination of the auto-relight indicator, followed by the engine fail light. He initiated an autorotation towards a clearing, but was unable to reach it. The helicopter impacted trees about 30 feet above the ground. During the inspection of the engine, the compressor discharge pressure line (Pc line) was removed at the compressor scroll, and compressed air was applied. Technicians reported air escaping at the Pc line's junction with the fuel control unit. The B-nut on the Pc line was loose at the fuel control unit. There was evidence of fretting on the B-nut fitting, and there were smears of orange torque seal material on the B-nut. No torque seal material was present on the B-nut fitting. The engine logbook indicated the fuel control unit was replaced by company mechanics 178 hours prior to the accident. ## Factual narrative On July 9, 2003, about 1800 Alaska daylight time, a Bell 206B helicopter, N111MT, sustained substantial damage during an in-flight collision with trees after a total loss of engine power, about 10 miles east of Aniak, Alaska. The helicopter was being operated as a visual flight rules (VFR) positioning flight under Title 14, CFR Part 91, by American Helicopters of Angleton, Texas. The solo commercial pilot received minor injuries. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The helicopter departed Red Devil airstrip, Alaska, about 1730, and was en route to Aniak when the accident occurred. In a written statement provided to the NTSB dated July 9, the pilot said that during cruise flight, he noticed a slow reduction of engine power, and a subsequent total loss of engine power. He said the first indication of power loss was the illumination of the auto-relight indicator, followed by the engine fail light. He started an autorotation, and selected a landing zone. The pilot said he was unable to make it to the selected landing zone in the heavily wooded area, and the helicopter impacted trees, about 30 feet above the ground. After recovery of the helicopter, the engine was sent to Premier Turbines of Wichita, Kansas, for inspection. During the inspection on November 3, the compressor discharge pressure line (Pc line) was removed at the compressor scroll, and compressed air was applied to the Pc line. During normal operation, the Pc line provides compressed air (bleed air) from the compressor section of the turbine engine, to operate the fuel control unit. Technicians at Premier reported that air was escaping from the Pc line fitting at the fuel control unit. The B-nut on the Pc line was loose at the fuel control unit. There was evidence of fretting on the B-nut fitting, and there were smears of orange torque seal material on the B-nut. No torque seal material was present on the B-nut fitting. The engine logbook indicates the fuel control unit was replaced by company mechanics 178 hours prior to the accident. There were no known mechanical anomalies with the helicopter prior to the accident. ## Aircraft - Registration: [N111MT](https://openairdocs.org/deregistered/N111MT-2013-08-06), registration cancelled 2013-08-06, S/N 1989, built 1976 (OpenAirDocs) - Reported make and model: Bell 206B - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 1989 - Airframe hours: 7701 - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: American Helicopters - Registered owner: Master Track, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, June 3, 2003, 26 hours before - Departed: RDV, Red Devil, AK - Destination: PANI, Aniak, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 36; injuries: minor; commercial; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; last flight review June 13, 2003; seat: right; flight hours: 1,786 total, 1,720 as pilot in command, 84 in the last 90 days, 72 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: 1,500 ft broken - Temperature: 75 °F ## 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 20030709033209A](https://openairdocs.org/incident/20030709033209A), Jul 9, 2003: Bell 206B, Chuathbaluk, AK, Substantial damage. (-23) On July 9, 2003, at 5:50PM, American helicopters, inc, pilot richard k. thielman experienced a complete engine failure while enroute from sleetmute, AK… 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.