The US Army wants helicopters to go faster. We don't know yet if army is willing or able to pay for that extra speed, but the desire is certainly there. Look around the exhibit hall of the Association of the United States Army's (AUSA) annual convention earlier this week, and the evidence was everywhere. On display were next-generation tiltrotors, and every combination of coaxial rotor-pusher-prop or ducted fan. Every idea was based on overcoming the inherent tendency of the retreating blade of a conventional rotor to stall after about 170kt. But Boeing added yet a new category to the speed discussion. If you looked carefully around its booth, a video on a loop showed a new kind of high-speed tandem rotor. Boeing had actually shown a previous version of the unloaded lift offset rotor (ULOR) concept at the American Helicopter Society safety forum in 2008. Since that event, the company has added two turboprops for extra thrust in forward flight.
But the key technology of this concept are the "wings" placed over each rotor. Boeing actually describes these devices as non-rotating blades, which augment the flapping effect of the hinged blades to overcome retreating blade stall at higher speeds than a conventional rotor.
Recent Comments