# NTSB LAX96LA315: Bell 47-G4A, N474GA, Guam, August 26, 1996 - Type: NTSB accident investigation - Classification: Accident · Fatal · Limited investigation · Final report - Date: August 26, 1996 - Place: Guam - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report August 25, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 29543 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX96LA315 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29543/pdf - Page: https://openairdocs.org/ntsb/LAX96LA315 ## Probable cause loss of tail rotor control due to improper maintenance. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Rotor failure/malfunction, cruise - rotor drive system,tail rotor drive shaft coupling - disconnected (cause) - maintenance - improper, other maintenance personnel (cause) - In flight collision with terrain/water, descent - uncontrolled ## Analysis The pilot was towing a banner offshore. Witnesses reported everything was normal until the banner fell free from the helicopter. At that point the helicopter started rotating to the right and descended into the bay. During the on-scene investigation, the retaining nut for the universal joint to yoke assembly on the tail rotor drive was found not engaged but retained the safety wire. The safety wire was broken on the last twist prior to entering the universal's affixing hole. The solid drive pin located in the aft universal and through the drive shaft was missing. ## Factual narrative On August 26, 1996, about 1115 hours local Guam standard time, a Bell 47-G4A, N474GA, was destroyed during a banner towing operation at Apra Harbor, Guam. The pilot was fatally injured. Visual meteorological conditions prevailed for the local area flight. The flight originated from a helipad at Tamuning, Guam, at 1030. According to witnesses, the helicopter was towing a banner about 200 feet msl at 30 to 35 miles per hour. Everything appeared to be normal until the banner fell free from the helicopter. At that point, the helicopter started to rotate to the right and descend. The banner entered the water before the helicopter. The helicopter continued rotating to the right until it impacted the waters of Apra Harbor. According to an FAA inspector on scene during the recovery, the retaining nut for the universal joint to yoke on the tail rotor drive was not engaged but retained the safety wire. The safety wire was broken on the last twist prior to entering the universal joint's affixing hole. The solid drive pin located in the aft universal joint and through the drive shaft was missing. ## Aircraft - Registration: [N474GA](https://openairdocs.org/deregistered/N474GA-2018-04-19), registration cancelled 2018-04-19, S/N 7580, built 1967 (OpenAirDocs) - Reported make and model: Bell 47-G4A - Registry model: [Bell 47G-4A](https://openairdocs.org/model/bell-47g-4a) (registry code 1181031) (OpenAirDocs) - Registry engine: [Lycoming VO-540 series](https://openairdocs.org/engine/lycoming-vo-540-series) (registry code 41534, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 7580 - Airframe hours: 2378 - Engines: Lycoming VO-540 305 horsepower reciprocating - Damage: Destroyed - Flight: Business, Part 91 - Operator: Hansen Helicopters Inc., doing business as Fanihi Air Service - Registered owner: Fanihi Air Service - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 17, 1996, 10 hours before - Departed: NONE, TAMUNING, OF ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; commercial; medical: class 2, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 2,750 total, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 6 knots - Visibility: 7 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 75 °F - Altimeter: 29.00 inHg ## 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 19960826023799A](https://openairdocs.org/incident/19960826023799A), Aug 26, 1996: Bell 47G4A, Tamuning, Guam, Destroyed, 1 fatal. Banner fell off helicopter at cruise. Plane spun to right into ocean. Had lost tail rotor drive pin. Lost control. 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.