Mitsubishi Heavy Industries (MHI) is working to reduce vibration levels in its new MH2000 helicopter, as part of several design refinements targeted at securing full Type A airworthiness certification for the civil machine.

Company efforts are focused on improving the twin-turboshaft helicopter, including better dynamic system damping and demonstration of single engine-out operations. The helicopter has been operating with limited Type B certification since June 1997, but full Japan Civil Aviation Bureau approval has been delayed.

According to MHI, vibration levels in the 10-seat cabin can be as high as ±0.2g. The intention is to reduce this to under ±0.1g. Helicopter sales general manager Shingo Noda claims that while this is not an impediment to Type A certification, he is "-not satisfied - and continuous improvements need to be made".

Some passive and active vibration control systems are being studied, including development of an actuator for the gearbox. A "floating floor" type damping system was incorporated into MHI's earlier RP1 test demonstrator machine, but this only serves to isolate the cabin, explains Noda.

To demonstrate engine reliability, MHI is planning further increases in the number of flight hours flown by the two prototypes. The first test machine, which is being used for the airworthiness programme, has logged 400h since its first flight in July 1996. This will be extended to 600h. A second company sales demonstrator is due to fly another 700h, in addition the 300h already completed.

MHI is hoping to secure Type A clearance ahead of the first MH2000 delivery scheduled for the end of the year to Tokyo-based sightseeing operator Excel Air Service. Initial low rate manufacturing is under way, with three production series machines on the line, says Noda.

Source: Flight International