# NTSB CEN18LA158: Robinson Helicopter R44, N444VH, East Troy, WI, May 4, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 4, 2018, 11:55 local (16:55 UTC) - Place: East Troy, WI - Coordinates: 42.796943, -88.372497 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.7969&lon=-88.3725&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA - SAIBs cited in the narratives: [SAIB CE-09-35](https://openairdocs.org/saib/CE-09-35) (OpenAirDocs) - NTSB case key (mKey): 97173 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA158 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97173/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97173 - Page: https://openairdocs.org/ntsb/CEN18LA158 ## Probable cause A partial loss of engine power for reasons that could not be determined based on the available information, which resulted in impact with terrain and dynamic rollover during the subsequent attempted landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Aircraft](https://openairdocs.org/ntsb-findings/01050000): Aircraft › Aircraft power plant · Unknown/Not determined; cases with it: [Robinson Helicopter R44, 1 case](https://openairdocs.org/ntsb-findings/01050000/cases.md?model=7640120), [All aircraft, 151 cases](https://openairdocs.org/ntsb-findings/01050000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-hover: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Robinson Helicopter R44, 10 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=7640120), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) ## Analysis The flight instructor and pilot receiving instruction were maneuvering to begin practice hovering when the helicopter experienced a lateral vibration. The instructor assumed control of the helicopter and attempted to land; however, the helicopter yawed to the left and both the instructor and pilot applied full right pedal to align the helicopter's nose with its ground track. Shortly thereafter, they heard the low rotor rpm horn and saw the associated warning light illuminate. The helicopter continued to the left, and as they lowered to the ground, the right skid caught on the grass and the helicopter experienced a dynamic rollover, resulting in substantial damage to the main rotor blades and fuselage. Examination of the airframe and engine revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation, and the helicopter had adequate fuel onboard for the flight. Although the weather conditions at the time of the accident were conducive to the formation of carburetor icing at glide and cruise power, the helicopter was equipped with a carburetor heat assist device, which automatically applied or reduced carburetor heat with changes in collective input. The reason for the partial loss of engine power could not be determined based on the available information. ## Factual narrative On May 4, 2018, about 1155 central daylight time, a Robinson R44 helicopter, N444VH, was substantially damaged when it was involved in an accident near East Troy, Wisconsin. The flight instructor and pilot receiving instruction were not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 training flight for Part 137 aerial application operations. The flight instructor directed the pilot to hover-taxi the helicopter to the grass runway to practice hovering. The pilot reported that once over the grass runway the helicopter experienced a lateral vibration which the instructor described as loud. The instructor took the flight controls to land. The instructor stated that the helicopter was about 5 to 7 feet above the ground, and as it started to settle, it yawed to the left 30° to 40°. The instructor and pilot both added full right pedal to align the nose of the helicopter with their ground track after the left yaw. About 2 feet above the ground, the low rotor rpm warning system light illuminated, and the associated horn sounded. The instructor raised the collective to “cushion the landing,” but the helicopter continued to the left and the right skid caught the ground. The helicopter entered a dynamic rollover and came to rest on its right side. The instructor reported that he had been completing refresher training for the “spray pilots” for about 2.5 hours before the accident flight. Neither the pilot nor the instructor reported using the carburetor heat during the flight. The helicopter sustained substantial damage to the main rotor system and fuselage. Examination of the airframe and engine revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. The instructor reported that the helicopter had an adequate amount of fuel onboard to complete the flight. The helicopter was equipped with a carburetor heat assist device, which automatically correlated application of carburetor heat with changes in collective setting to reduce pilot workload; lowering collective applied carburetor heat and raising collective reduced carburetor heat. The temperature and dewpoint at the time of the accident were conducive to the formation of serious carburetor icing at cruise power settings, per the Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35, Carburetor Icing Prevention. ## Aircraft - Registration: [N444VH](https://openairdocs.org/aircraft/N444VH), registered now, S/N 0571, built 1999 (OpenAirDocs) - Reported make and model: ROBINSON HELICOPTER R44 (UNDESIGNAT) - Registry model: [Robinson Helicopter R44](https://openairdocs.org/model/robinson-helicopter-r44) (registry code 7640120) (OpenAirDocs) - Registry engine: [Lycoming 0-540 series](https://openairdocs.org/engine/lycoming-0-540-series) (registry code 41532, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 0571 - Year built: 1999 - Engines: LYCOMING O-540 SERIES 260 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Mf Helicopters LLC - Registered owner: Mf Helicopters LLC - Airworthiness certificate: Special, Restricted (Special) - Destination: Same as departure - Airport: 57C, East Troy Muni, runway 18, 2,446 × 75 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 26; injuries: none; commercial, flight instructor; medical: class 2, with waivers/limitations; last flight review August 3, 2016; seat: left; restraint: 3-point; flight hours: 1,804.4 total, 1,102.2 in this make and model, 1,755.6 as pilot in command, 66.3 in the last 90 days, 37.1 in the last 30 days, 3.6 in the last 24 hours - Pilot; age 28; injuries: none; commercial; instrument ratings: helicopter; medical: class 2, without waivers/limitations; last flight review November 22, 2017; seat: right; restraint: 5-point; flight hours: 328 total, 0 in this make and model, 2,727 as pilot in command, 43.5 in the last 90 days, 16.9 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 9 knots, gusting 14 - Visibility: 10 statute miles - Temperature: 61 °F, dew point 52 °F - Altimeter: 29.88 inHg - Observed at: KBUU, 7 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 20180504004609A](https://openairdocs.org/incident/20180504004609A), May 4, 2018: Robinson Helicopter R44, East Troy, WI, Substantial damage. On may 4, 2018 clear VFR day the flight instructor and commercial pilot took off to conduct hover training with agricultural equipment installed. While taxing… ## Docket (5 files) The files NTSB released with the investigation on February 22, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97173. 29.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (instructor pilot) (item 1, PDF, 10 pages, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11722408&FileExtension=pdf&FileName=Completed%206120%20from%20Instructor%20Pilot_Redacted2-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (pilot receiving instruction) (item 2, PDF, 10 pages, 15.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11722741&FileExtension=pdf&FileName=Completed%206120%20from%20Student%20Pilot_Redacted2-Rel.pdf - Accident site photographs (item 3, PDF, 2 pages, 2.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11722548&FileExtension=pdf&FileName=Accident%20site%20photos-Rel.pdf - Engine logs (item 4, PDF, 5 pages, 6.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11723208&FileExtension=pdf&FileName=N444VH%20eng%20log3_Redacted-Rel.pdf - Memorandum of record for FAA exam (item 5, PDF, 1 page, 131 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11661359&FileExtension=pdf&FileName=Memorandum%20of%20Record%20for%20FAA%20Exam-Rel.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.