Vertolety Rossii (Russian Helicopter) made an interesting announcement recently in Moscow. They plan to spend $1 billion on researching what they are calling a fifth-generation helicopter. What are the requirements? It must be radar invisible, have extended range (no specifics on what that means,) be equipped with an intellectual arms system, be able to combat fighter jets and reach speeds of 370 mph. They believe that with additional government funding they could have it built in as soon as five years.
The figure of 370 mph is of particular interest to me. Currently, the speed record for a production helicopter was set back in 1986 using a modified Westland Lynx ZB500.
Westland G-Lynx Record Holder
That aircraft managed to reach 249.1 mph. What has been preventing us from going faster? Several items, including retreating blade stall which is a problem introduced due to the advancing blade generating more lift than the retreating blade. Another thing to consider is wave drag and the problems of supersonic blade tips. Apparently, they have a plan for how to get around these problems. Maybe they will be using a tilt-rotor setup such as the Osprey V-22? If so, can you really call it a helicopter still? But wait, was the Lynx really the fastest?
Sikorsky S-69
Back in the early 1970s, Sikorsky came up with a way to eliminate the retreating blade stall problem. They developed the S-69 as part of the Advancing Blade Concept program which used a co-axial design and a “feathering” of the blades. This eliminated retreating blade stall and allowed the advancing blades to carry the load. Maximum speed is listed as 322 mph. If Kamov is involved perhaps we’ll see (or not see) an evolution of the KA-50? Alternatively, if they don’t go with a co-axial setup, I’ll be really interested to know how they overcome RBS at such a high speed. What are your thoughts?