# NTSB CHI95LA187: Bell 47J2A, N470RA, Elkhorn, WI, June 19, 1995 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 19, 1995, 14:40 local (19:40 UTC) - Place: Elkhorn, WI - Coordinates: 42.669048, -88.540809 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.6690&lon=-88.5408&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report March 6, 1996 - Report: Approved by Office Director - NTSB case key (mKey): 9916 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI95LA187 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9916/pdf - Page: https://openairdocs.org/ntsb/CHI95LA187 ## Probable cause loss of power as a result of an intake valve failure due to improper maintenance performed during the major engine overhaul, and pilot misjudgment of the flare during autorotation. ## 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 - engine assembly,valve,intake - failure (cause) - maintenance,major repair - improper, other maintenance personnel (cause) - Forced landing, emergency descent/landing - autorotation - performed, pilot in command - Hard landing, emergency landing - flare - misjudged, pilot in command (cause) - rotor drive system,tail rotor drive shaft - blade strike ## Analysis THE PILOT REPORTED THAT HE WAS CRUISING AT ABOUT 1,000 FEET WHEN THE ENGINE LOST POWER. AN AUTOROTATION WAS INITIATED. DURING THE LANDING PHASE (CYCLIC FLARE), THE MAIN ROTOR STRUCK THE TAILROTOR DRIVE SHAFT. AN EXAMINATION OF THE ENGINE REVEALED THAT THE NUMBER TWO CYLINDER INTAKE VALVE HAD FAILED IN THE TOP RADIUS (NECK AREA) OF THE VALVE KEEPER RECESS, CAUSING DAMAGE TO THE CYLINDER COMBUSTION CHAMBER AND PISTON. AN INSPECTION OF THE ENGINE LOGBOOKS INDICATED THAT AN IDENTICAL FAILURE HAD OCCURRED EIGHT HOURS PREVIOUSLY. FURTHER INSPECTION REVEALED THAT THE MAJOR ENGINE OVERHAUL, WHICH HAD BEEN CONDUCTED 27 HOURS PRIOR TO THE ACCIDENT, HAD NOT BEEN PERFORMED IN ACCORDANCE WITH THE MANUFACTURER'S PROCEDURES AND SPECIFICATIONS. ## Factual narrative On June 19, 1995, at 1440 central daylight time, a Bell 47J2A helicopter, N470RA, sustained substantial damage as a result of an engine failure and subsequent autorotation. The accident took place near Elkhorn, Wisconsin. The airline transport pilot and the passenger reported no injury. The 14 CFR Part 91 flight departed East Troy Airport, East Troy, Wisconsin, on a local flight. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he was cruising at about 1,000 feet above ground level when the engine failed. An autorotation was initiated. During the landing phase (cyclic flare), the main rotor struck the tailrotor drive shaft. An examination of the engine revealed that the number two cylinder intake valve had failed in the top radius (necked area) of the valve keeper recess, causing damage to the cylinder combustion chamber and piston. An inspection of the engine logbooks indicated that an identical failure had occurred eight hours previously. The first failure occurred on a factory new cylinder assembly, and the second on a "used" cylinder of undetermined time in service. Further inspection revealed that the major engine overhaul, which had been conducted 27 hours prior to the accident, had not been performed in accordance with the manufacturer's procedures and specifications. (See attachments) ## Aircraft - Registration: N470RA (not matched to a registry record) - Reported make and model: BELL 47J2A - Category: Helicopter - Serial number: 3719 - Airframe hours: 6100 - Engines: LYCOMING VO-540-B1B3 305 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: John M. Wilson - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 30, 1995, 27 hours before - Departed: 57C, EAST TROY, WI ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 40; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 1, unknown; seat: right; flight hours: 9,600 total, 200 in this make and model, 7,200 as pilot in command, 90 in the last 90 days, 30 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 10 knots - Visibility: 8 statute miles - Lowest ceiling: none - Temperature: 90 °F - Altimeter: 30.00 inHg - Observed at: UES, 28 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 19950619022669A](https://openairdocs.org/incident/19950619022669A), Jun 19, 1995: Bell 47J2A, Elkhorn, WI, Substantial damage. Lost power at cruise. Autorotated. During flare rotors hit tail drive shaft. NR2 cyl valve failed. Improper flare. (-23) inflight (cruise) engine failure-… 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.