# NTSB FTW95LA056: Bell 206B, N2183P, Natchitoches, LA, November 29, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 29, 1994, 14:32 local (20:32 UTC) - Place: Natchitoches, LA - Coordinates: 31.750812, -93.089714 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=31.7508&lon=-93.0897&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report June 19, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 19313 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW95LA056 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/19313/pdf - Page: https://openairdocs.org/ntsb/FTW95LA056 ## Probable cause THE DELAYED FLARE AND THE IMPROPER TOUCHDOWN BY THE PILOT IN COMMAND. FACTORS WERE THE OPERATION OF THE AIRCRAFT WITH KNOWN DEFICIENCIES BY THE OPERATOR AND THE PILOT, DELAYED MAINTENANCE, AND, AN ENGINE COMPRESSOR ASSEMBLY STALL, COMBINED WITH EROSION AND CORROSION OF THE STATOR VANES WHICH RESULTED IN A COMPLETE LOSS OF POWER. ## 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 - compressor assembly,stator vane - stall (contributing factor) - compressor assembly,stator vane - corroded (contributing factor) - compressor assembly,stator vane - eroded (contributing factor) - operation with known deficiencies in equipment - continued, company/operator management (contributing factor) - operation with known deficiencies in equipment - continued, pilot in command (contributing factor) - maintenance - delayed, company maintenance personnel (contributing factor) - Forced landing, descent - emergency - Hard landing, landing - flare/touchdown - flare - delayed, pilot in command (cause) - touchdown - improper, pilot in command (cause) ## Analysis DURING A MAINTENANCE TEST FLIGHT, THE HELICOPTER EXPERIENCED A LOSS OF ENGINE POWER DUE TO MECHANICAL REASONS. THE MAINTENANCE HISTORY REVEALED THAT THE ENGINE HAD EXPERIENCED A SERIES OF COMPRESSOR STALLS DURING THE LAST 132 HOURS OF FLIGHT. COMPANY MANAGEMENT ELECTED TO DEFER REQUIRED MAINTENANCE UNTIL THEIR 'BUSY SEASON WAS OVER.' THE METALLURGICAL ANALYSIS SHOWED THAT INTERGRANULAR CORROSION AND EROSION OF THE STATOR VANES COMBINED TO EFFECTIVELY WEAKEN THE INDIVIDUAL VANES STRUCTURALLY. A COMPRESSOR STALL WAS EXPERIENCED. THE PILOT PERFORMED AN AUTOROTATION AND DURING TOUCHDOWN THE MAIN ROTOR BLADES SEVERED THE TAIL BOOM. ## Factual narrative On November 29, 1994, at 1432 central standard time, a Bell 206B, N2183P, was destroyed during a forced landing near Natchitoches, Louisiana. The commercial pilot and the three passengers were not injured. Visual meteorological conditions prevailed for the local 14 CFR Part 91 flight. In a written report submitted by the operator, they stated that the aircraft was on a maintenance test flight to evaluate the engine performance. They further stated that the reason for the test flight was to determine the effects of previously reported compressor stalls during the last 132 hours of operation. The operator stated that they had three maintenance personnel onboard, 2 were engine specialists, conducting the testing. During an interview conducted by a Federal Aviation Administrator (FAA) Inspector, the pilot stated that one of the onboard technicians monitoring the test equipment requested that he move the starter/generator switch to the "OFF" position during one of the tests. After completion of the test the pilot "rolled" the throttle back to flight idle and moved the starter/generator switch to the "ON" position. The throttle was then "rolled" back to the full on and the pilot heard a "rapid popping" sound. The engine sustained a total power loss and the pilot initiated an autorotation from 1,200 above the ground, onto a golf course. Maintenance personal reported that management had deferred maintenance on the aircraft, following the compressor stalls, "until the end of our busy season." An FAA Inspector reported that during the forced landing the fuselage and dynamic components sustained damage and that the tailboom was severed by a main rotor strike. The case halves were taken to Materials Analysis,Inc., Dallas, Texas, for metallurgical analysis. They determined that two dynamic processes had weakened the stator vanes - erosion and intergranular corrosion (see enclosed metallurgical report). The report further states "a compressor stall alone would not normally apply sufficient load to the stator vanes to cause an overload failure; however, the combined effects of vane erosion and pre-existing intergranular cracks in the vanes could effectively weaken the individual vanes to such a degree that unusual load applications could result in unanticipated vane overload failures." ## Aircraft - Registration: N2183P (not matched to a registry record) - Reported make and model: BELL 206B - Category: Helicopter - Serial number: 3470 - Airframe hours: 7455 - Engines: ALLISON 250-C20 B 420 horsepower turbo shaft - Damage: Destroyed - Flight: Part 91 - Registered owner: International Paper Company - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, October 15, 1994, 100 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; commercial; instrument ratings: helicopter; medical: class 1, valid medical--w/ waivers/lim; seat: right; flight hours: 2,427 total, 67 in this make and model, 2,300 as pilot in command, 62 in the last 90 days, 35 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 90° at 5 knots - Visibility: 15 statute miles - Lowest ceiling: 25,000 ft broken - Temperature: 66 °F, dew point 34 °F - Altimeter: 30.00 inHg - Observed at: SHV, 90 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 19941129039879A](https://openairdocs.org/incident/19941129039879A), Nov 29, 1994: Bell 206B, Natchitoches, LA, Destroyed. Test flight. Lost power. Had history compressor stalls. Deferred inspection. Engine stalled. Stator vanes erroded. 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.