# NTSB CEN22LA234: Robinson Helicopter R44, N94WC, Henderson, TX, June 6, 2022 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: June 6, 2022, 09:50 local (14:50 UTC) - Place: Henderson, TX - Coordinates: 32.141723, -94.851728 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.1417&lon=-94.8517&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Robinson, Lycoming, FAA FSDO - NTSB case key (mKey): 105203 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN22LA234 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105203/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105203 - Page: https://openairdocs.org/ntsb/CEN22LA234 ## Probable cause The partial loss of engine power in a hover due to a stuck exhaust valve. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating)](https://openairdocs.org/ntsb-findings/01058500): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Robinson Helicopter R44, 3 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md?model=7640120), [All aircraft, 497 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md) - [Performance/control parameters: yaw control](https://openairdocs.org/ntsb-findings/01062024): Aircraft › Aircraft oper/perf/capability · Not attained/maintained; cases with it: [Robinson Helicopter R44, 6 cases](https://openairdocs.org/ntsb-findings/01062024/cases.md?model=7640120), [All aircraft, 149 cases](https://openairdocs.org/ntsb-findings/01062024/cases.md) - [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Damaged/degraded (probable cause); cases with it: [Robinson Helicopter R44, 4 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=7640120), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-hover: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Robinson Helicopter R44, 7 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=7640120), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Maneuvering-hover: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Robinson Helicopter R44, 43 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=7640120), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) ## Analysis The helicopter pilot was practicing hover takeoffs and landings in a crosswind. The passenger reported that, while hovering before a landing, the helicopter shuddered, and the left skid contacted the ground. The helicopter rolled onto its left side. The helicopter sustained substantial damage to the main rotor blades, fuselage, and tail boom. Examination of the helicopter’s flight control systems and main and tail rotor drive systems did not show any preimpact anomalies that would have precluded normal operation. Examination of the No. 2 cylinder revealed that the exhaust push rod was bent and the exhaust valve was stuck. Borescope inspection of the No. 2 cylinder showed that the exhaust valve had contacted the piston and the intake valve appeared to be recessed in the No. 2 valve seat. The loss of engine power was most likely due to the stuck exhaust valve on the No. 2 cylinder. ## Factual narrative On June 6, 2022, about 0950 central daylight time, a Robinson R44 helicopter, N94WC, was substantially damaged when it was involved in an accident near Henderson, Texas. The pilot sustained serious injuries and the passenger sustained minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The passenger reported that the pilot was practicing hover takeoffs and landings in a crosswind. She stated that, while hovering before a landing, the helicopter shuddered, and the left skid contacted the ground. The helicopter rolled onto its left side. The helicopter sustained substantial damage to the main rotor blades and tail boom. Examination of the helicopter’s flight control systems and main and tail rotor drive systems did not show any preimpact anomalies. During the engine examination the valve covers, and bottom sparkplugs were removed. The crankshaft was rotated by hand and thumb compression was obtained at all cylinders except the No. 2 cylinder. Examination of the No. 2 cylinder revealed that the exhaust push rod was bent and the exhaust valve was found stuck. Borescope inspection of the No. 2 cylinder showed that the exhaust valve had contacted the piston. The intake valve appeared to be recessed in the No. 2 valve seat. A review of the engine logbooks showed no indication of compliance with Lycoming Engines Mandatory Service Bulletin 388C, “Procedure to Determine Exhaust Valve and Guide Condition.” The service bulletin recommended compliance every 300 hours or if valve sticking is suspected and cautioned that “Failure to comply with the provisions of this publication could result in engine failure due to excessive carbon build up between the valve guide and valve stem resulting in sticking valves or broken exhaust valves...” According to Robinson, past experiences of a stuck valve in a R44 have resulted in the pilots reporting some or all the following symptoms: vibrations felt through the airframe, popping, or misfiring out of the exhaust, loss of power, low rotor RPM and/or engine RPM fluctuations. ## Aircraft - Registration: [N94WC](https://openairdocs.org/deregistered/N94WC-2024-02-26), registration cancelled 2024-02-26, S/N 0691, built 1999 (OpenAirDocs) - Reported make and model: ROBINSON HELICOPTER R44 - 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: 0691 - Year built: 1999 - Engines: Lycoming IO-540 280 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Destination: Same as departure - Airport: RFI, Henderson County Airport - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; injuries: serious; private, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; seat: right; restraint: 4-point; flight hours: 3,300 total, 50 in this make and model, 20 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 7 knots, gusting 16 - Visibility: 10 statute miles - Lowest ceiling: 20,200 ft overcast - Temperature: 82 °F, dew point 68 °F - Altimeter: 29.79 inHg - Observed at: KRFI, 1 nm away - METAR: METAR KRFI 061459Z AUTO 19007G16KT 150V220 10SM OVC202 28/20 A2979 RMK A02 ## 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 20220606022129A](https://openairdocs.org/incident/20220606022129A), Jun 6, 2022: Robinson Helicopter R44, Henderson, TX, Substantial damage. On June 6, 2022, about 0950 central standard time, a Robinson R44 helicopter,[privacy data omitted], was substantially damaged when it was involved in an… ## Docket (7 files) The files NTSB released with the investigation on April 25, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105203. 6.8 MB in all. - Memorandum for the record summary of NTSB iic and passenger conversation CEN22LA343 (item 1, PDF, 1 page, 90 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16967344&FileExtension=pdf&FileName=Memorandum%20for%20the%20Record%20Summary%20of%20NTSB%20IIC%20and%20Passenger%20Conversation%20CEN22LA343-Rel.pdf - Airframe and engine examination summary CEN22LA234 (item 2, PDF, 6 pages, 218 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16968070&FileExtension=pdf&FileName=Airframe%20and%20Engine%20Examination%20Summary%20CEN22LA234-Rel.pdf - Memorandum for the record effects of stuck valves (item 3, PDF, 1 page, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16968080&FileExtension=pdf&FileName=Memorandum%20for%20the%20Record%20Effects%20of%20Stuck%20Valves%20CEN22LA234-Rel.pdf - Lycoming service bulletin 388C (item 4, PDF, 13 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16967739&FileExtension=pdf&FileName=Lycoming%20Service%20Bulletin%20388C%20CEN22LA234-Rel.pdf - Certificate of party representative Lycoming CEN22L234 (item 5, PDF, 1 page, 132 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16967974&FileExtension=pdf&FileName=Certificate%20of%20Party%20Representative%20Lycoming%20CEN22L234_Redacted-Rel.pdf - Certificate of party representative Robinson CEN22LA234 (item 6, PDF, 1 page, 4.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16967729&FileExtension=pdf&FileName=Certificate%20of%20Party%20Representative%20Robinson%20CEN22LA234_Redacted-Rel.pdf - Investigation photographs CEN22LA234 (item 7, PDF, 3 pages, 610 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16967826&FileExtension=pdf&FileName=Investigation%20Photographs%20CEN22LA234-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.