# NTSB ERA17LA126: Eurocopter AS 350, N413LP, San Juan, PR, February 21, 2017 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 21, 2017, 10:15 local (14:15 UTC) - Place: San Juan, PR - Coordinates: 18.456666, -66.098335 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=18.4567&lon=-66.0983&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Defining event: [Autorotation: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report January 25, 2018 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 94847 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA17LA126 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/94847/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=94847 - Page: https://openairdocs.org/ntsb/ERA17LA126 ## Probable cause The flight instructor's incorrect manipulations of the twist grip throttle control during a practice autorotation, which resulted in an engine overspeed and subsequent fire. ## 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 use/operation (probable cause); cases with it: [Eurocopter AS 350 B3, 1 case](https://openairdocs.org/ntsb-findings/01057320/cases.md?model=8680954), [All aircraft, 59 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md) - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Instructor/check pilot (probable cause); cases with it: [Eurocopter AS 350 B3, 4 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=8680954), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Autorotation: Miscellaneous/other](https://openairdocs.org/ntsb-events/900); cases with it: [Eurocopter AS 350 B3, 6 cases](https://openairdocs.org/ntsb-events/900/sequence.md?model=8680954), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md) - [Autorotation: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) (defining event); cases with it: [Eurocopter AS 350 B3, 2 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=8680954), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) ## Analysis The pilot/owner of the turbine helicopter was practicing autorotations with a flight instructor. After completing several autorotations uneventfully, the instructor asked if he could perform one, and the pilot agreed. Near the flare at the end of the maneuver, the pilot heard the engine overrev, followed by an Nr (rotor speed) aural warning, followed by a fire warning light illumination on the instrument panel. After landing, the pilot exited the helicopter with a fire extinguisher and attempted to extinguish an engine fire. Review of data downloaded from a vehicle-engine multifunction display and digital engine control unit revealed that the first failure recorded during the flight indicated that the gas generator rotation speed (N1) reached an out-of-limit value. At that time, the fuel regulation was in mixed mode, as the collective twist grip throttle control was out of the "flight" detent and the pilot was manually controlling the throttle. A second failure was recorded 2 seconds later, which indicated that the free turbine rotation speed (N2) reached an out-of-limit value. The failure was triggered by the maximum recorded value of 545 rpm, which equated to a turbine speed (Nr) of 140%. The engine's freewheeling turbine was designed to separate turbine blades at 150% Nr in order to prevent the turbine disc separating at 170% Nr. It is likely that the flight instructor excessively opened the fuel metering unit via the twist grip throttle manual control, which resulted in an engine overspeed, turbine blade separation, and subsequent engine fire. ## Factual narrative On February 21, 2017, about 1015 Atlantic standard time, an Airbus Helicopters (Eurocopter) AS 350 B3, N413LP, operated by the commercial pilot, was substantially damaged during a practice autorotation at Fernando Luis Ribas Dominicci Airport (TJIG), San Juan, Puerto Rico. The flight instructor and commercial pilot were not injured. The instructional flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the flight that originated from TJIG about 0900.According to the flight instructor's written statement, he was the pilot-in-command for the flight and the commercial pilot/owner of the helicopter was practicing autorotations. During recovery from the last 180° autorotation, the flight instructor noticed that the engine rpm continued to increase and exceeded limitations, followed by a vibration in the helicopter. He then immediately landed on a grass area near a runway. After the landing, a mechanic told him that the helicopter's engine was on fire. The flight instructor completed the engine fire procedure and exited the helicopter. According to the commercial pilot's written statement, he had completed several training maneuvers and autorotations uneventfully. The flight instructor then asked if he could perform an autorotation and the commercial pilot agreed. During the flare at the end of the autorotation, the commercial pilot heard the engine overrev, followed by an Nr (rotor speed) aural warning, followed by a fire warning light illumination on the instrument panel. After landing, the commercial pilot exited the helicopter with a fire extinguisher and attempted to extinguish an engine fire. Review of airport security video revealed that the helicopter was descending to a grass area adjacent to the runway. About 30 feet above ground level, smoke began emitting from the helicopter and it climbed out of the video frame. It then descended back into the video frame and landed on the grass while smoke continued to emit from the helicopter. Examination of the helicopter by a Federal Aviation Administration inspector revealed that the fire resulted in damage to the engine deck support structure and a portion of the tail rotor drive shaft. A vehicle and engine multifunction display (VEMD), digital engine control unit (DECU), hydromechanical unit (HMU), and assembly valve were retained for examination and data download at the manufacturers' facilities under the supervision of the Bureau d'Enquetes et d'Analyses (BEA) in France. Examination and testing of the HMU and assembly valve did not reveal any anomalies that would have precluded normal engine operation. Review of data downloaded from the VEMD and DECU revealed that during the accident flight, the first failure recorded by both computers was an NG/N1 failure, respectively. The failure was recorded at 1 hour, 13 minutes, 18 seconds (1:13:18) into the 1-hour, 14-minute flight by the VEMD and1:13:27 by the DECU. The recorded failure indicated that the gas generator rotation speed (N1) reached an out of limit value. At that time, the fuel regulation was in mixed mode as the collective twist grip throttle control was out of the "flight" detent and the pilot was manually controlling the throttle. A second failure was recorded 2 seconds later, which indicated that the free turbine rotation speed (N2) reached an out of limit value. The failure was triggered by the maximum recorded value of 545 rpm, which equated to an Nr of 140%. According to a representative from the engine manufacturer, the engine's freewheeling turbine was designed for its turbine blades to separate at 150% turbine speed. The design was to prevent the turbine disc from separating at a turbine speed of 170%. During his examination of the engine, the representative observed evidence consistent with the turbine blades separating, resulting in an engine fire. ## Aircraft - Registration: [N413LP](https://openairdocs.org/aircraft/N413LP), registered now, S/N 3228, built 1999 (OpenAirDocs) - Reported make and model: EUROCOPTER AS 350 (B3) - Registry model: [Eurocopter AS 350 B3](https://openairdocs.org/model/eurocopter-as-350-b3) (registry code 8680954) (OpenAirDocs) - Registry engine: [Turbomeca ARRIEL-1SER](https://openairdocs.org/engine/turbomeca-arriel-1ser) (registry code 60030, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 3228 - Year built: 1999 - Airframe hours: 1846 - Engines: Turbomeca Arriel 2B 871 horsepower turbo shaft - Damage: Substantial damage - Fire: In-Flight - Flight: Instructional, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, June 9, 2016, 59 hours before - Departed: TJIG, San Juan, PR - Destination: TJIG, San Juan, PR - Airport: TJIG, Fernando Luis Ribas Dominicci - Equipment: Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 37; injuries: none; airline transport, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane, helicopter; medical: class 1, without waivers/limitations; last flight review September 20, 2016; seat: left; restraint: 3-point; flight hours: 6,250 total, 950 in this make and model, 5,500 as pilot in command, 280 in the last 90 days, 40 in the last 30 days, 3 in the last 24 hours - Pilot; age 74; injuries: none; commercial; airplane ratings: single-engine land; medical: class 1, with waivers/limitations; last flight review January 1, 2016; seat: right; restraint: 3-point; flight hours: 8,467 total, 5,200 in this make and model, 8,467 as pilot in command, 31 in the last 90 days, 12 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 6 knots, gusting 12 - Visibility: 8 statute miles - Lowest ceiling: 5,500 ft broken - Temperature: 73 °F, dew point 66 °F - Altimeter: 29.95 inHg - Observed at: TJIG ## 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 20170221001339A](https://openairdocs.org/incident/20170221001339A), Feb 21, 2017: Eurocopter AS 350 B3, San Juan, PR, Substantial damage. On February 21, 2017 the PIC of an Eurocopter executed an autorotation after noticed that the engine RPM continued to increase and exceeded limitations with… ## Other investigations on N413LP (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 ERA11CA433](https://openairdocs.org/ntsb/ERA11CA433), Jul 30, 2011: Eurocopter AS 350 B3 (N413LP), Humacao, PR, substantial damage. Probable cause: The pilot's failure to maintain clearance from a building during landing. ## Docket (10 files) The files NTSB released with the investigation on October 30, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=94847. 10.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457431&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Airport Security Video Excerpt (45 Seconds in MP4 Format, 14MB) (item 2, .PDF, 162 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457432&FileExtension=.PDF&FileName=Airport%20Security%20Video%20Excerpt%20(45%20Seconds%20in%20MP4%20Format,%2014MB)-Master.PDF - Interview Summary (item 3, .PDF, 130 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457433&FileExtension=.PDF&FileName=Interview%20Summary-Master.PDF - Helicopter Manufacturer Report of VEMD Data Download (item 4, .PDF, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457434&FileExtension=.PDF&FileName=Helicopter%20Manufacturer%20Report%20of%20VEMD%20Data%20Download-Master.PDF - Engine Manufacturer Report of DECU Data Download (item 5, .PDF, 452 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457438&FileExtension=.PDF&FileName=Engine%20Manufacturer%20Report%20of%20DECU%20Data%20Download-Master.PDF - Engine Manufacturer Report of HMU and Assembly Valve Tests (item 6, .PDF, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457439&FileExtension=.PDF&FileName=Engine%20Manufacturer%20Report%20of%20HMU%20and%20Assembly%20Valve%20Tests-Master.PDF - BEA Report of VEMD and DECU Data Download (item 7, .PDF, 425 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457441&FileExtension=.PDF&FileName=BEA%20Report%20of%20VEMD%20and%20DECU%20Data%20Download-Master.PDF - BEA Report of HUM and Assembly Valve Tests (item 8, .PDF, 322 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457442&FileExtension=.PDF&FileName=BEA%20Report%20of%20HUM%20and%20Assembly%20Valve%20Tests-Master.PDF - Photo Array (item 9, .PDF, 3 photos, 961 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40457444&FileExtension=.PDF&FileName=Photo%20Array-Master.PDF - Evidence Control Form (item 10, .PDF, 232 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40460012&FileExtension=.PDF&FileName=Evidence%20Control%20Form-Master.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.