# NTSB LAX03TA043: Bell 47G-3B-1, N48020, Panaca, NV, December 1, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: December 1, 2002, 13:10 local (21:10 UTC) - Place: Panaca, NV - Coordinates: 37.790279, -114.425003 - Nearby events: https://openairdocs.org/map.md?lat=37.7903&lon=-114.4250&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 28, 2004 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 56161 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX03TA043 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/56161/pdf - Page: https://openairdocs.org/ntsb/LAX03TA043 ## Probable cause separation of the no. 6 cylinder intake valve head from the valve stem, which resulted in a loss of engine power. The mechanism responsible for the valve failure is unknown. ## 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, maneuvering - engine assembly,valve,intake - separation (cause) - Forced landing, emergency descent/landing - autorotation - initiated, pilot in command - Hard landing, landing - flare/touchdown - misc rotorcraft,main rotor/tail boom contact - terrain condition - ground ## Analysis The helicopter experienced a loss of engine power and landed hard during an autorotation, severing the tail boom. The number 6 cylinder's intake valve separated, with the valve's head wedged in the intake valve seat bore. Removal of the rocker box cover on that cylinder revealed that the spring retainer was broken into numerous pieces. The piston head showed over 15 impressions consistent in dimension to that of the valve head. After examining the number 6 cylinder, a metallurgist determined that the valve failed in between the intake valve head and the valve stem. ## Factual narrative On December 1, 2002, about 1310 Pacific standard time, a Bell 47G-3B-1, N48020, experienced a loss of engine power and landed hard during an autorotation near Panaca, Nevada. The Bureau of Land Management was operating the helicopter under the provisions of 14 CFR Part 91. The commercial pilot, the sole occupant, was not injured; the helicopter sustained substantial damage. Visual meteorological conditions prevailed, and a company flight plan had been filed. The local public use positioning flight originated from Caliente, Nevada, about 1200. The pilot was positioning the helicopter to perform a horse herding operation for the Bureau of Land Management at the time of the accident. Two witnesses reported seeing two grey smoke emissions from the engine prior to a loss of engine power and hard landing, severing the tail boom. In a written statement, the mechanic who regularly preformed the maintenance on the helicopter, reported that earlier in the year the helicopter underwent a 1,000-hour engine inspection, which included an engine overhaul; it was returned to service on April 30, 2002. The cylinder assemblies used for the overhaul were purchased from Engine Components, Inc., in San Antonio, Texas. The maintenance tag attached on the cylinders attested that "the repair made to the unit listed on reverse side was made and inspected in accordance with current regulations of the FAA [Federal Aviation Administration] and the part is Airworthy and approved for return to service." The mechanic further stated that he conducted an engine examination after the accident under the supervision of the FAA. Upon removal of the induction tubes and the induction manifold, the mechanic discovered internal discoloration similar to that for the exhaust tubes. He removed the number 6 cylinder and noted that the intake valve was broken, with the valve's head wedged in the intake valve seat bore. Removal of the rocker box cover on that cylinder revealed that the spring retainer was broken into numerous pieces. The piston head showed over 15 impressions consistent in dimensions to that of the valve head. The mechanic added that at the time of the accident, the cylinder had accumulated 10 hours since overhaul and the engine had accumulated 110.3 hours since the last overhaul. The cylinder was sent to Engine Components, Inc., for further examination under the auspice of the FAA. The mechanic's complete written account is appended to this report in the public docket. Engine Components, Inc., completed a technical report in summation of their findings. In pertinent part, the director of quality and metallurgy stated that the retainer failed due to overload. He opined that during engine operation the valve fractured first, resulting in the valve stem impacting the retainer and keys leading to their facture and deformation. He noted that the broken valve was a new part supplied by Lycoming during the cylinder overhaul. The complete report is appended to the report in the public docket. ## Aircraft - Registration: [N48020](https://openairdocs.org/aircraft/N48020), registered now, S/N 2812, built 1967 (OpenAirDocs) - Reported make and model: Bell 47G-3B-1 - Registry model: [Bell 47G-3B-1](https://openairdocs.org/model/bell-47g-3b-1) (registry code 1181028) (OpenAirDocs) - Registry engine: [Lycoming TVO-435-GIA](https://openairdocs.org/engine/lycoming-tvo-435-gia) (registry code 41526, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 2812 - Airframe hours: 7471 - Engines: Lycoming TVO-435-B1A 270 horsepower reciprocating - Damage: Substantial damage - Flight: Public aircraft, Part 91 - Operator: Bureau of Land Managment - Registered owner: Clifford J. Heaverne - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, October 31, 2002, 100 hours before - Departed: Caliente, NV - Destination: Panaca, NV ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 59; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 29,351 total, 16,120 in this make and model, 26,934 as pilot in command, 51 in the last 90 days, 17 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 45 °F, dew point 32 °F - Altimeter: 30.12 inHg - Observed at: CDC, 63 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 20021201031599A](https://openairdocs.org/incident/20021201031599A), Dec 1, 2002: Bell 47G3B1, Panaca, NV, Substantial damage. (-23) While herding wild horses engine lost power at approximately 35 feet AGL in a left turn. Aircraft contacted terrain in a heels low attitude causing the… ## Other investigations on N48020 (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 SEA03LA189](https://openairdocs.org/ntsb/SEA03LA189), Sep 12, 2003: Bell 47G-3B-1 (N48020), Diamond, OR, substantial damage. Probable cause: Loss of engine power for undetermined reasons during hover. 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.