# NTSB NYC06LA175: Enstrom 280C, N5691B, Danville, WV, July 15, 2006 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: July 15, 2006, 09:15 local (13:15 UTC) - Place: Danville, WV - Coordinates: 38.083332, -80.83889 - Nearby events: https://openairdocs.org/map.md?lat=38.0833&lon=-80.8389&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report April 30, 2008 - Report: Approved by Office Director - Parties: Enstrom Helicopter, FAA/FSDO - NTSB case key (mKey): 64117 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC06LA175 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/64117/pdf - Page: https://openairdocs.org/ntsb/NYC06LA175 ## Probable cause A partial failure of the override clutch assembly. A contributing factor to the accident was the manufacturer's inadequate inspection procedures of the override clutch assembly following a tail rotor strike. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - normal - rotor drive system,clutch assembly - failure,partial (cause) - maintenance,service bulletin/letter - inadequate, manufacturer (contributing factor) - Hard landing, emergency landing - terrain condition - ground ## Analysis Approximately 7 minutes after takeoff, the pilot of the helicopter heard a "loud snap," and experienced a 5 to 10 degree right yaw. This occurred a second time, 5 to 8 seconds later. The pilot declared an emergency and elected to make a precautionary landing. During the approach, he experienced a third snap sound and yaw movement. The helicopter was at an airspeed below 20 knots, and about 8 to 10 feet above the ground, when the pilot heard a bang, and felt ground contact. The helicopter rolled to the left, and the main rotor blades contacted the ground. Examination of the helicopter confirmed drive train continuity to the main and tail rotor drive shafts. A ground scar, consistent with tail rotor ground contact, was observed about 60 feet from the main wreckage. The tail rotor gear box, drive shaft and blade assembly were located about 250 feet from the main wreckage. Examination of the tail rotor gearbox and adjacent components did not reveal any preexisting damage; however, it also did not reveal any indications of rotational damage. Examination of the override clutch assembly, which drove both the main transmission and the tail rotor system, revealed preexisting damage that occurred at an undeterminable time prior to the accident. The accident helicopter was involved in a previous hard landing accident about 13 months, and 87 hours of operation prior, during which, it had a tail rotor strike, and a fractured tail rotor drive shaft. The override clutch assembly was not removed for inspection after that accident; nor was it specifically required to be removed and inspected per the manufacturer's maintenance guidelines for "Special Inspection for Sudden Stoppage, Main and/or Tail Rotor Blade Strikes." ## Factual narrative On July 15, 2006, about 0915 eastern daylight time, an Enstrom 280C, N5691B, was substantially damaged during a precautionary landing in Danville, West Virginia. The certificated commercial pilot sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the flight that departed the Logan County Airport (6L4), Logan, West Virginia, destined for the Greater Portsmouth Regional Airport, Portsmouth (PMH), Ohio. The solo cross-country instructional flight was conducted under 14 Code of Federal Regulations Part 91. According to his written statement, the pilot said he heard a "loud snap" and experienced a 5 to 10 degree right yaw, approximately 7 minutes after takeoff. Approximately 5 to 8 seconds later, he heard a second snapping sound, and again experienced a 5 to 10 degree right yaw. The pilot declared an emergency and elected to perform a precautionary landing at a strip mine. During the approach, he experienced a third snap sound and yaw movement. The helicopter was at an airspeed below 20 knots, and about 8 to 10 feet above the ground, when the pilot heard a bang, and felt ground contact. The helicopter rolled to the left, and the main rotor blades contacted the ground. Examination of the helicopter was conducted by a Federal Aviation Administration (FAA) inspector and representatives from Enstrom Helicopter. Drive train continuity was confirmed to the main and tail rotor drive shafts. A ground scar, consistent with tail rotor ground contact, was observed about 60 feet from the main wreckage. The tail rotor gear box, drive shaft and blade assembly were located about 250 feet from the main wreckage. The tail rotor assembly, 90-degree gearbox and the override clutch assembly were retained for further examination. Examination of the tail rotor gearbox and adjacent components at the National Transportation Safety Board Materials Laboratory, Washington DC, did not reveal any preexisting damage or failures. In addition, the examination did not reveal any indications of rotational damage. The override clutch assembly, which drove both the main transmission and the tail rotor system, was removed and examined at its manufacturer, under the supervision of an FAA inspector. According to the manufacturer's teardown report, damage was found in the clutch assembly that was consistent with impact damage sustained during the accident; however, damage was also found that was consistent with preexisting damage that occurred at an undeterminable time prior to the accident. The override clutch assembly had accumulated approximately 1,804.6 hours since new, and had a time between overhaul (TBO) interval of 2,400 hours. The accident helicopter was involved in a previous hard landing accident on August 12, 2005, during which, it experienced a tail rotor strike, and a fractured tail rotor drive shaft. According to maintenance records, the override clutch assembly was not removed for inspection after that accident. Review of the helicopter's maintenance manual did not reveal any information calling for an inspection of the override clutch assembly after a tail rotor blade strike. Enstrom service information letter (SIL) No. 0088, "Special Inspection for Sudden Stoppage, Main and/or Tail Rotor Blade Strikes" was in effect at the time of the accident; however, the SIL required that the override clutch assembly be inspected only during main rotor strikes and or sudden stoppage. According to the maintenance manual, SIL's were to be considered part of the maintenance manual, and were used to transmit information, recommendations, and general service instructions to the customer. The clutch assembly would not have been disassembled and inspected during routine 100-hour and annual inspection maintenance intervals. The helicopter had been operated approximately 87 hours since the previous accident. The override clutch assembly teardown report further stated that because the clutch assembly was not disassembled and inspected after the tail strike in August 2005, it was not possible to determine the amount of internal damage that the clutch assembly sustained at the time of that event, and may have accumulated during the subsequent hours of operation. The pilot held a commercial pilot certificate, with ratings for single and multiengine land airplanes, and was training for a rotorcraft rating with private pilot privileges. He reported 1,060 hours of total flight experience, which included about 30 hours in helicopters. ## Aircraft - Registration: [N5691B](https://openairdocs.org/deregistered/N5691B-2017-06-30), registration cancelled 2017-06-30, S/N 1180, built 1979 (OpenAirDocs) - Reported make and model: Enstrom 280C - Registry model: [Enstrom Helicopter 280C](https://openairdocs.org/model/enstrom-helicopter-280c) (registry code 3300505) (OpenAirDocs) - Registry engine: [Lycoming HI0-360 series](https://openairdocs.org/engine/lycoming-hi0-360-series) (registry code 41553, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 1180 - Airframe hours: 1804 - Engines: Lycoming HIO-360-EIAD 205 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Marpat Aviation LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, June 1, 2006, 11 hours before - Departed: 6L4, Logan, WV - Destination: PMH, Portsmouth, OH - Airport: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Student pilot; age 52; injuries: minor; commercial; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane; medical: class 3, with waivers/limitations; seat: left; flight hours: 1,060 total, 27 in this make and model, 25 in the last 90 days, 8 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 250° at 7 knots - Visibility: 7 statute miles - Lowest ceiling: 1,500 ft overcast - Temperature: 75 °F, dew point 70 °F - Altimeter: 30.06 inHg - Observed at: CRW, 24 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 20060715022609A](https://openairdocs.org/incident/20060715022609A), Jul 15, 2006: Enstrm 280C, Danville, WV, Substantial damage. (-23) According to his written statement, the pilot said while on a solo cross country flight he heard a "loud snap" and experienced a 5 to 10 degree right… ## Other investigations on N5691B (1) 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. - [NTSB IAD05LA122](https://openairdocs.org/ntsb/IAD05LA122), Aug 12, 2005: Enstrom 280C (N5691B), Saulsville, WV, substantial damage. Probable cause: The pilot's inadequate remedial action following a loss of control during the landing approach. 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.