# NTSB ATL96LA129: Bell 47G-4A (Soloy), N23PH, Belmont, MS, September 19, 1996 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: September 19, 1996, 12:45 local (17:45 UTC) - Place: Belmont, MS - Coordinates: 34.499095, -88.20095 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.4991&lon=-88.2010&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report July 28, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 3761 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL96LA129 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/3761/pdf - Page: https://openairdocs.org/ntsb/ATL96LA129 ## Probable cause failure of the aft universal joint of the tail rotor drive shaft, due to inadequate lubrication by company maintenance personnel. A factor relating to the accident was the pilot's delay in discontinuing the flight after noting a progressively worse tail rotor drive vibration. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - aerial application - rotor drive system - vibration - remedial action - delayed, pilot in command (contributing factor) - rotor drive system,tail rotor drive shaft coupling - seized (cause) - maintenance,lubrication - not performed, company maintenance personnel (cause) - Forced landing, emergency descent/landing - autorotation - performed, pilot in command - In flight collision with object, emergency landing - object - tree(s) ## Analysis During an aerial application operation, the pilot was making east and west swath runs. He reported that he had dispensed about half of his load, when he noted a vibration in the tail rotor pedals during a turn-around maneuver. He conducted three more swath runs with the vibration becoming progressively worse during each turn-around. Subsequently, during the fourth turn-around, the tail rotor drive was lost when the tail rotor drive shaft aft universal joint failed. Examination of the universal joint revealed a lack of lubricant, and the tail rotor drive shaft was discolored blue. There was no log book entry to indicate that the universal joint had been lubricated in the 150 plus hours of operation since the last inspection. The manufacturer's recommended maintenance practices included lubrication of the universal joint after each 50 hours of operation. ## Factual narrative On September 19, 1996, about 1245 central daylight time, a Bell 47G-4A Soloy, collided with trees during an emergency descent, near Belmont, Mississippi. The helicopter was operated by Provine Helicopter Service, Inc. under the provisions of Title 14 CFR Part 137, and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the aerial application flight. There were minor injuries to the commercial pilot, and the helicopter was substantially damaged. Origination of the flight was a remote operating site near Belmont, Mississippi, about 1242, on the same day. According to the pilot, he experienced increasing vibrations in the rudder pedals during successive spray runs. Subsequently, he lost yaw control as the helicopter began rotating, to the right, about the vertical axis. An autorotation was executed into a heavily wooded area. The FAA inspector who examined the helicopter and the operator indicated that there was extensive damage to the main rotor blades and fuselage, with virtually no damage to the tail rotor blades. Additionally, they reported that the aft universal joint for the tail rotor drive shaft exhibited little evidence of lubrication. The airworthiness inspector who examined the helicopter and its records reported that a 1200 hour inspection was completed on July 30, 1996, at an aircraft time of 9696.2 hours. The repair station operator that conducted the inspection stated that he used red lubricant to lubricate the bearings and the universal joint that failed. No red grease was found in the universal joint during its disassembly following the accident. The tail rotor drive shaft exhibited blue discoloration The manufacturer's helicopter maintenance manual recommends lubricating the tail rotor bearings and universal joint at 50 hour intervals. No log book entries were found to indicate that the helicopter had been lubricated in the 153.7 operating hours since the 1200 hour inspection. ## Aircraft - Registration: [N23PH](https://openairdocs.org/deregistered/N23PH-2000-08-08), registration cancelled 2000-08-08, S/N 7506 (OpenAirDocs) - Reported make and model: Bell 47G-4A (SOLOY) (47G-4A (SO) - Registry model: [Bell 47G-4A](https://openairdocs.org/model/bell-47g-4a) (registry code 1181031) (OpenAirDocs) - Category: Helicopter - Serial number: 7506 - Airframe hours: 9850 - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Provine Helicopter Service,Inc - Airworthiness certificate: Standard, Normal; Special, Restricted (Special) - Last inspection: Continuous airworthiness, July 30, 1996, 154 hours before - Departed: NONE ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 31; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane, helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 2,550 total, 924 in this make and model, 1,452 as pilot in command, 164 in the last 90 days, 143 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 10° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 55 °F - Altimeter: 30.00 inHg - Observed at: TUP, 35 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 19960919029369A](https://openairdocs.org/incident/19960919029369A), Sep 19, 1996: Bell 47G4A, Belmont, MS, Substantial damage. Aircraft lost control and crashed into trees. (.4)during an aerial application operation, the pilot was making east and west swath runs. He reported that he… 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.