Transmission complexity could impede progress as researchers bid to reduce noise
Engine-driven fans that would only be operated during take-off and then stowed for cruise flight is one propulsion solution being studied for an ultra-quiet blended wing body (BWB) airliner.
As part of the Silent Aircraft Initiative project conducted by Cambridge University and the Massachusetts Institute of Technology, UK researchers have studied the configuration in a bid to minimise aircraft noise on take- off and landing.
To reduce jet noise while producing the same thrust requires a larger air volume travelling at slower speed. To accommodate the different air volume and engine requirements for take-off and cruise, one option is to use dedicated propulsion systems.
"At cruise [the take-off fans] would be stowed away," says associate researcher Dr Cesare Hall. "The big problem with this option is the shafts and gearbox arrangement needed to drive the fans."
Attempts to combine the multiple transmission systems to save space and weight have been problematic. Unless this problem is resolved, this propulsion solution for future airliners is unlikely to become a reality.
The silent aircraft work has studied various options to quieten operations, including embedding engines in the airframe of a BWB (Flight International, 1-8 June 2004) and large variable exhaust nozzle.
ROB COPPINGER / LONDON
Source: Flight International
