That’s a pretty impressive goal. About 130-140 knots tends to be the speed of a fast helicopter. The manufacturer’s “never exceed speed” for the Bell Huey AH-1 Cobra, long the core of the U.S. attack helicopter fleet, is 190 knots; it’s 197 knots for Boeing’s newer AH-64 Apache, which is replacing the Cobra. The Sikorsky’s speed of 250 knots is an unofficial record for a helicopter.
But what Connecticut-based Sikorsky really has to worry about is not Seattle/Chicago’s Boeing or Fort Worth’s Bell, but our Cabernet-swilling friends across the pond, whose Gitanes will surely be extinguished to their delight when they cook along at 220 knots (250 mph) in Eurocopter’s hybrid X3, which was unveiled recently. You can read an analysis here, and can see it in action, and a discussion of the design concepts, below:
We may just find raspberry berets strewn across the countryside near Eurocopter HQ in Marignane, France. But while those suave pilots are busy tweeting “Sacre bleu! LOL“, people who don’t work at Jane’s Defence Weekly might wonder WTF is the difference between the two, and how important are those extra 30 knots to the real war out there — the battle for defense contracts?
Both the Eurocopter X3 and the Sikorsky X2 are compound helicopters or gyrodynes, with overhead rotor systems allowing them to take off and land vertically, but horizontal propellers that allow them to attain much faster speeds. The main design difference is that the Sikorsky utilizes overhead coaxial rotors, in which two parallel sets of rotors rotate in opposite direction. The system was tested on Sikorsky’s earlier S-69, a purely experimental aircraft. The Sikorsky X2 Demonstrator first flew in 2008.
Other coaxial systems are already in use, but have not neared the speed of the Sikorsky. The Russian helicopter bureau Kamov is known for using coaxial design; their Kamov KA-50 can achieve a speed of 204 knots in a dive.