The pair of “low-observable” Sikorsky Black Hawks used in the raid by U.S. forces against terrorist Osama bin Laden’s Pakistani compound May 2 were kitted with a variety of stealth and radar-defeating features that had been in development since the 1970s, and maybe longer. The helicopters came to light after one had to be left behind and intentionally detonated after apparently clipping a compound wall and making a hard landing.
Helicopter noise reduction
A bilateral project between NASA and German aerospace research center DLR is expected to focus on the role rotor tip vortices play in helicopter noise by recording vortex velocity fields and rotor-blade deformations by using a test stand with a variety of high-speed cameras, lasers and LEDs that will make the vortices visible. Eventually research will progress to actual helicopters.
The lobbying association for the French helicopter industry, the Union Française de l’Hélicoptère (UFH), is raising concerns about gestating noise rules that could practically ban commercial flights from urban areas. The association fears legislators are writing such a rule with input only from heli- port neighbors, some of whom are members of anti-helicopter associations.
Helicopter manufacturers are exploring a number of technologies to reduce noise, both that perceived from the ground and inside the cabin. European manufacturers are working on several demonstration programs to reduce noise by changing the helicopter’s airframe dynamics.
Reducing vibration and noise is key to the goal of gaining public acceptance of the rotorcraft as a routine mode of transport. A Boeing team has now successfully made use of advanced materials to develop and test a new helicopter rotor that could go a long way toward unlocking the vehicle’s potential.