Although a helicopter is unbeatable when it comes to manoeuvrability, it still cannot match the high speeds of propeller driven airplanes. It thus comes as no surprise that the helicopter industry is looking for a solution. This quest is not new. As long ago as the 1960s, Lockheed developed the fast AH-56A Cheyenne, which used a pusher propeller to achieve a maximum speed of 244mph in level flight.
As was the case with the development of the Cheyenne, the US military is often the driving force behind these innovations. Indeed, in the 2010s, it is again the US Air Force that has formulated a new goal with its Joint Multi Role (JMR) technology demonstration program. This program was the predecessor of the Future Vertical Lift (FVL) scheme, which has the far-reaching aim of replacing the UH-60 Blackhawk, the CH-47 Chinook, the AH-64 Apache and the OH-58 Kiowa models by 2030. An important requirement of the program is a much higher cruise speed than can currently be realized with a conventional helicopter configuration.
In this context, it should not come as a surprise that Eurocopter has developed the fast X3 technology demonstrator. The key idea behind this helicopter is to: gradually slow down the main rotor speed in order to prevent the excessive drag of the advancing blades; and avoid retreating blade stall by unloading the rotor system. To generate enough lift in this situation, two small stub wings are attached to the frame. They also mount the propellers that give the machine the forward thrust that is necessary for the high forward speed. To solve the main rotor's torque effect, a different pitch is applied to the two propellers. This mechanism is also used for yaw control.
Eurocopter built the X3 prototype by using components from other models. The fuselage and main rotor were taken from the EC155 (Dauphin), while the turbo shaft engines are from the NH90 and the gearboxes that drive the propellers are from the EC175.
Eurocopter started test flights in September 2010, eventually achieving a speed of 255 knots (293mph) in level flight in July 2013. In the same year, the company finished its test program, and the X3 was put on static display at Musée de l'Air in 2014.
Although successful in terms of its speed specifications, there are some critics of the configuration, in particular the two large propellers on each side of the aircraft, which could compromise a broad mission profile. However, a patent filed by Eurocopter reveals that the company also has ideas about a configuration with two pusher propellers attached to a tail wing, which would resolve this issue.
In 2013, Eurocopter opted for the JMR program with the X3. However, due to high costs and the fact that the company had to transfer part of its intellectual property to the US, it withdrew from this program. Eurocopter also tried to join the Armed Aerial Scout (AAS) program. Unfortunately, it was not chosen to take part and, to make matters even worse, the program has been put on a hold all together at the time of writing (2014).
Currently, Eurocopter is focusing on the civil high speed market for medium-weight utility and offshore helicopters, and claims that it can hit the market around 2020. By that time, it will probably have to face competition from Sikorsky, which is also developing high speed helicopters with its X2 technology demonstrator.