THE ACTIVE VIBRATION-control system of the EH Industries EH101 helicopter could soon be applied to a fixed-wing aircraft. Brian Main, chief engineer on the programme at EHI partner Westland, will not identify the potential airframe application, apart from hinting that it is twin-engine, and for a military application.

The EH101 system uses ten sensors to collect vibration inputs, which are processed by a central computer, which sends anti-phase actuation instructions to four hydraulic struts connected to the main gearbox mounting. Main says that the system damps 17.5Hz vibrations at the gearbox so well that the accelerations measured at the cabin floor are reduced to one-seventh of what they would be without control.

Following the simultaneous US/UK/Italian certification at the end of 1994 of the -300 and -500 (civil and ramp-loading utility) versions of the EH101, the company is now embarking on a 6,000h flying programme aimed at demonstrating the type's ability in actual service conditions (Flight International, 14-20 December, 1994).

Two aircraft, one based at Brindisi in Italy, and the other working in the North Sea oilfields, will be used in this trial. The company does not yet have a civil customer for the EH101, but says that it is "very hopeful" that a North Sea operator will place the first order "before the end of 1995". It predicts sales of 200 civil machines over a 25-year period, along with military sales of 500.

Source: Flight International