Andrew Doyle/

AN INNOVATIVE power-transmission system for the next-generation of advanced helicopters has been unveiled by ZF Luftfahrttechnik (ZFL), which claims its design gives scope for significant weight savings and increased reliability.

Friedrichshafen, Germany-based ZFL presented the idea to delegates attending the Aerospace Transmissions Technology into the 21st Century seminar, which it hosted on behalf of the UK's Institution of Mechanical Engineers on 28 September.

Central to the concept is the integrated dynamic system (IDS), which combines the aircraft's flight-control mechanisms and the gearbox into a single, compact casing. The IDS differs from conventional configurations, in that the swash plate, control rods and pitch-control mechanism, are usually located outside the gear-box exposed to the environment and requiring separate lubrication.

Together with a low-height gear train design and single-blade control system, the use of IDS achieves what is effectively a "single link" between the engine and the rotor blades. Single-blade control involves replacing rigid control rods between the swash plate and the rotor blades with servo-hydraulic or electrical actuators, which can be adjusted individually.

Jurgen Riech, manager for gear technology at ZFL, claims that the IDS eliminates the need for a external rotor-shaft because the interface between the drive gear and rotor head is at a relatively low height. In addition, lubrication can be controlled under "clean" conditions within the single casing. The gearbox is constructed as a two- stage system - consisting of an input stage and a collector stage to combine the power of the engines.

As well as low weight and high reliability, says Riech, benefits would include reduced fuel consumption and noise emissions, improved aerodynamic efficiency and the possibility an enlarged passenger cabin.

One drawback could be reduced maintainability, as access to components for overhaul or replacement might be restricted because of the compact design.

Source: Flight International