# NTSB DEN08LA138: Bell 206L-1, N832AH, Heber Springs, AR, August 11, 2008 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 11, 2008, 15:30 local (20:30 UTC) - Place: Heber Springs, AR - Coordinates: 35.51889, -91.816665 - Nearby events: https://openairdocs.org/map.md?lat=35.5189&lon=-91.8167&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 29, 2009 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 68680 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN08LA138 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/68680/pdf - Page: https://openairdocs.org/ntsb/DEN08LA138 ## Probable cause the improper installation of the PC line on the engine which resulted in a partial loss of engine power. Contributing to the accident was the trees encountered during the forced landing. ## 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: [All aircraft, 59 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Terrain](https://openairdocs.org/ntsb-findings/03021000): Environmental issues › Physical environment · Contributed to outcome (probable cause); cases with it: [All aircraft, 267 cases](https://openairdocs.org/ntsb-findings/03021000/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: [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Maneuvering: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Autorotation: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The helicopter had been conducting external load operations on the day of the accident and had just departed after refueling. While transporting an empty container on the long line at 300 feet above ground level, the engine "spooled down". The pilot released the external load, executed a 180-degree turn and autorotation. During the forced landing, the helicopter landed hard in a tree farm and impacted trees, rolled over and came to rest on its right side. The pilot shut off the fuel and exited the helicopter. Examination of the engine showed the PC line B-nut was found disconnected. The last engine maintenance which involved the removal and reinstallation of the PC line was 67.1 hours prior, during a scheduled turbine change. No slippage marks (torque paint) were noted on the fitting. The engine manufacturer's maintenance manual procedures document the proper installation procedures, which include slippage markings. ## Factual narrative On August 11, 2008, approximately 1530 central daylight time, a Bell 206L-1 single-engine helicopter, N832AH, sustained substantial damage during a forced landing following a partial loss of engine power while maneuvering near Heber Springs, Arkansas. The airline transport pilot, who was the sole occupant, was not injured. The helicopter was registered to and operated by Hillsboro Aviation Inc., Hillsboro, Oregon. Visual meteorological conditions prevailed, and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 133 external load flight. The flight departed a remote heli-spot location approximately 20 minutes prior the accident. According to the operator, the helicopter had been conducting external load operations on the day of the accident and had just departed after refueling. While transporting an empty container on the long line at 300 feet above ground level, the engine "spooled down". The pilot released the external load, executed a 180-degree turn and autorotation. During the forced landing, the helicopter landed hard in a tree farm and impacted trees, rolled over and came to rest on its right side. The pilot shut off the fuel and exited the helicopter. Examination of the helicopter revealed the tail boom was separated, the main rotor blades were bent, and the right side of the fuselage was damaged. A Federal Aviation Administration inspector, who spoke with a company mechanic, reported that a PC line B-nut was found disconnected on the Rolls Royce 250-C30P engine. The mechanic reported that the last engine maintenance which involved the removal and reinstallation of the PC line was 67.1 hours prior, during a scheduled turbine change. No slippage marks (torque paint) were noted on the fitting. According to the Rolls Royce 250-C30 Series Operation and Maintenance manual, section 72-00-00, "Proper tightening of engine tubing connections is critical to flight safety...Tubing B-nuts used in installations exposed to a high degree of vibration and pressure surges are subject to torque relaxation when improperly tightened...Old slippage marks (torque paint) shall be completely removed, using torque paint remover, and reapplied each time the B-nut is tightened." In 1990 (Revision 1, dated February 5, 2007), Rolls Royce issued an "Alert Commercial Service Letter: Maintenance Warning - External Lines". The letter background states that Rolls Royce continues to be involved in investigations of aircraft accidents and incidents which are attributed to improper alignment, clamping, and torquing of engine tubing during installation. The letter documents examples and causes of the failures of tube assemblies. ## Aircraft - Registration: N832AH (not matched to a registry record) - Reported make and model: BELL 206L-1 - Category: Helicopter - Serial number: 45560 - Airframe hours: 9504 - Engines: Rolls-Royce 250-C30P 726 horsepower turbo shaft - Damage: Substantial damage - Flight: External load, Part 133 - Registered owner: Hillsboro Aviation Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, August 1, 2008 - Departed: Heber Springs, AR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 67; injuries: none; flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 2, without waivers/limitations; last flight review April 1, 2008; seat: right; flight hours: 21,000 total, 6,000 in this make and model, 228 in the last 90 days, 94 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 90° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 66 °F - Altimeter: 29.90 inHg 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.