Flight-testing in Europe has shown that 50% reductions in a helicopter's acoustic footprint during landings are possible.
Using the German aerospace agency DLR's Eurocopter EC135-FHS research helicopter, a landing profile involving a climb followed by a steep descending trajectory was carried out.
A "tunnel in the sky" display, designed by the DLR Institute of Flight Systems, helped the pilot keep to the optimised flight plan. The tunnel display is generated using speed, altitude and attitude data.
Another possible noise reduction technique is to allow the helicopter's shrouded tail rotor to auto-rotate. The DLR found this gave substantial noise reductions, but it needs a rudder on the helicopter's tail to stop main-rotor induced yaw movement.
This flight testing was conducted under a 54-month, €32.4 million ($45.7 million) European Union technology integration project in support of a passenger and environmentally friendly helicopter, also known as Friendcopter. The final report is to be published soon. The project's co-ordinator for Friendcopter, Eurocopter's Valentin Kloeppel, says: "Work is continuing under the Clean Sky programme's green rotorcraft project for noise abatement."
A total of 34 institutions were involved in Friendcopter including Aircelle, Cranfield University, Eurocopter, EADS, Milan Polytechnic, French aerospace agency Onera, Riga technical university and Turbomeca.
Source: Flight International
