The need for speed
As soon as the early pioneers solved the complex aerodynamic puzzle that makes a helicopter safely leave the ground, the next obsession has been to fly them as fast as possible.
The early days of the helicopter saw an abundance of different configurations as engineers searched for ways to get around the main limiting factor of a helicopter’s airspeed – retreating blade stall.
Most were based on a hybrid or compound VTOL design, such as the Sikorsky S-72 or the Lockheed XFV, but the difficulty of developing such aircraft without the aid of computer design or digital flight controls consigned most to the dust-bin.
Now Russian Helicopters is looking to break rotorcraft speed limits with its high-speed helicopter testbed based on a Mi-24K attack helicopter – shown for the first time at the MAKS exhibition last week.
The company is planning a full-scale testing and evaluation campaign in 2016, with the testbed intended to test a new rotor system with an all-new rotor hub and composite blades.
Most working helicopters today tend to have a maximum speed of around 270 km/h – with only the V-22 and AW609 tiltrotors getting around this paradigm by combining the advantages of VTOL with the fixed wing’s speed and range.
While the company achieved the design goal for the X2 in 2010, when it was flown at a speed of 250 knots (460 km/h) in level flight, the record was short-lived and was broken by Eurocopter’s X3 high-speed compound in 2013 with a speed of 472 km/h.
Given both aircraft were compound designs, the world speed record for a helicopter remains with the modified Westland Lynx that achieved 400 km/h way back in 1986.
Coincidentally this is the same speed Russian Helicopters plans to reach with the first phase of its high-speed testbed, although the presence of wings on its fuselage will probably disqualify it from claiming the record.