Federal investigators have all but officially dismissed sabotage and are studying a frayed control cable as the cause of the crash June 6 near Sutton, Mass., of a helicopter detailed to the party of Jordan's King Hussein, investigators said yesterday.
The four persons aboard the new Sikorsky S76B, all Sikorksy employes, were killed. Because of rainy weather, Hussein and his party elected to travel by automobile from Bedford, Mass., to Stratford, Conn., where Hussein visited Sikorsky's base.
The Federal Bureau of Investigation has identified an electrical wire found in the luggage compartment as part of a test instrument, probably a voltmeter. One of the passengers was an electronic technician. The investigators said fire may have started when the helicopter spun wildly out of control and a flying object in the cabin severed a fuel line.
The FBI is continuing to test other pieces of recovered luggage, but "the possibility of sabotage is fading further into the background," a source close to the investigation said.
Meanwhile, National Transportation Safety Board investigators said they found a 15-to-18-foot length of tail-rotor control cable wrapped around a gearbox. The tail rotor provides directional stability and is necessary to counteract centrifugal force set up by the main rotor. If a tail rotor fails, a helicopter will spin out of control.
Sikorsky warned owners of its new S76B models about the findings yesterday, telling them not to fly their helicopters until the control cable is inspected by a Sikorsky representative. Only 10 of the helicopters are in service, a Sikorsky spokesman said.
The Sikorsky alert said that "during inspection on several aircraft, chafing has been observed on tail-rotor control cables." Federal officials said they do not yet understand the source of the chafing and cannot say conclusively that chafing caused the accident.