NTSB Identification: IAD99RA032
Accident occurred Friday, February 26, 1999 in Belo Horizonte, Brazil
Aircraft: Bell 407, registration:
Injuries: 2 Fatal,1 Serious.
This is preliminary information, subject to change, and may contain errors. The foreign authority was the source of this information.
About 1230 local Brazilian time, February 26, 1999, a Bell 407 helicopter, registration PT-YVI, Bell serial no. 53119, operated by Banco Rural, sustained substantial damage following loss of tail rotor control and an autorotation to a hard landing. Of the three persons on board, the commercially certificated pilot sustained serious injuries and both passengers were fatally injured. Visual meteorological conditions prevailed for the corporate flight that originated at a ranch, approximately 20 nautical miles northeast of Pampulha Airport, near the city of Belo Horizonte. No flight plan was filed. The pilot was in radio contact with Pampulha Tower. The flight was conducted under Brazilian CAA flight rules.
The pilot reported that the helicopter was in cruise flight, straight and level at 110 knots indicated airspeed (KIAS), 3,500 feet mean sea level (MSL) and 700 feet above ground level (AGL), when he felt the left rudder pedal move forcefully forward and heard a loud bang. The helicopter yawed left and pitched nose-down. He regained control and performed an autorotation to a hard landing, sustaining back injuries. Both passengers, including a bank president, then exited the helicopter and ran into still-turning main rotor blades. Part of the tailboom, with the tail gearbox and tail rotor assembly still attached, was found approximately 800 yards from the impact site.
The weather was witnessed as visual meteorological conditions, in drizzle, beneath an approximately 1,000 foot overcast.
The helicopter was powered by a Rolls-Royce Allison 250-C47 engine, serial no. 847151, with a time since new of 341 hours.
The pilot, age 51, had flown approximately 12,000 helicopter hours, including 340 hours in the Bell 407.
Under the head of the investigation commission, from Terceiro Servico Regional de Aviacao Civil, Brazil, accompanied by an accredited representative from the Transportation Safety Board (TSB), Canada, and investigators from Bell Helicopter, Fort Worth, Texas, and Rolls Royce Allison, Indianapolis, Indiana, examinations of the tail rotor assembly were conducted, and two previous Bell 407 partial tailboom separations were reviewed. Prior to the February 26, 1999, accident, an FAA airworthiness directive had lowered the Bell 407 velocity, never exceed (Vne), from 140 KIAS to 110 KIAS. Bell Helicopter provided a technical bulletin that incorporated a left pedal stop, and if installed, the Vne was permitted back up to 125 KIAS. Following the February 26, accident, flight was forbidden without the pedal stop and, if installed, limited to 110 KIAS. Subsequently, Bell Helicopter incorporated an engineering change that effectively moved the tail rotor yoke farther outboard from the tailboom and provided other changes at the tail rotor assembly. With the engineering changes incorporated, Vne has been permitted back to 130 KIAS.
The tail rotor servo was bench-tested and disassembled at its manufacturer, Hydraulic Research Textron, Valencia, California, under NTSB supervision (Engineering Investigator Frank Hilldrup, from Headquarters, Washington, D.C.), with TSB Canada and Bell Helicopter investigators also present. The servo tested properly and no evidence was found of a previous mechanical problem. Contamination was found in the hydraulic fluid and is being further examined by TSB Canada.
For further information contact: Head of Investigation Commission, Lieutenant Colonel Antonio Augusto Walther de Almeida, tel. (55) 21 532-5431 or 240-3701, fax (55) 21 240-3701.
U.S. Accredited Representative: Thomas R. Conroy, NTSB, Washington, D.C., tel. (202) 314-6314.
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