Eurocopter’s X3

June 19, 2012 by Tim McAdams

The X3 is a hybrid aircraft that offers the speed of a turboprop-powered airplane and the full hover flight capabilities of a helicopter. It’s equipped with two Rolls-Royce Turbomeca RTM322 turboshaft engines, producing 2,309 hp each, powering a standard EC155 five-bladed main rotor system and two propellers on short-span fixed wings. The X3 first flew September 6th, 2010 and then in May of 2011 achieved a speed of 232 knots while using only 80 percent of prop shaft torque limit. The X3 is a proof of concept aircraft intended to demonstrate advanced technologies that could be used on high-speed helicopters in the next ten years.

The X3’s rotor speed is slowed down to reduce the Mach number of the advancing blade tip. To prevent retreating blade stall at high airspeeds the load on the rotor is reduced while the short span wings provide up to 40% lift instead. Also, the X3 does not have a tail rotor. So to counter the torque of the main rotor at low speed prop differential thrust is used. At high speed, remaining anti-torque function is realized by vertical fin flaps.

In May of 2012 the American Helicopter Society awarded Eurocopter’s X3 development team the Howard Hughes award for an outstanding improvement in fundamental helicopter technology brought to fruition during the preceding year.

5 Responses to “Eurocopter’s X3”

  1. Avi Weiss Says:

    While I’m certain clever transmission design will enable either engine to drive both props should an ENGINE fail, Would be interesting to understand how the system is designed to react should one of the wing-mounted PROPS or DRIVE SHAFT fail. Casual observation would seem to yield that any failure of the side-props would require immediate power cessation and auto to prevent unmanageable yaw. I’m guessing there are some clever “active control systems” in place to help mitigate some of these scenarios.

    Would also be interesting to hear the FAAs take on what sort of pilot rating would be required to fly this, and what kind of training would be required: powered lift? multi-engine? single-prop?

  2. Frank Holt Says:

    The X3 taxied past my office at Arlington, TX airport yesterday and I was astounded at this amazing aircraft. As a pilot one always enjoys seeing new flying machines. While developement of such wonderful machines usually improves something else in aviation by vitrue of the research and testing that we all benefit from; one wonders if the tremendous cost of purchase, maintaining, and crew training for such an aircraft is worth the extra 50kts of speed.

    I am thankful for all the forward thinkers and investors for the future of aviation!!

  3. John F Says:

    @Avi:

    Regarding your concern of prop or shaft failure to a propeller, here are my thoughts:

    I would expect that the individual drives to the wings could be disconnected in the event of a failure, however in certain parts of the envelope it would be essential to maintain power to the remaining prop in order to provide for anti-yaw control. Given reversable propellers, either side could be made to perform this function as an emergency measure. Only if both side forward thrust units were to fail would you have a serious problem, akin to a tail rotor failure, and then only if forward speed was insufficient to allow the rudders to provide adequate yaw control.

    I can see technology being available to make this project work in a practical sense; Frank’s point about the KIAS:Dollar ratio is more likely the limiting factor.

  4. Gary Byer Says:

    The Moller VTOL (vertical take-of or landing) craft located at Davis, CA is the answer. No rotor blade used-no rotor to fail. If our government would just see it, Moller Sky Car for what it is and what it can do they would fund it. Check it out “Moller.com”

  5. Jim Borger Says:

    My problem is loading/unloading with the engines running. It is not unusual for me to fly in an enviroment during the winter months where the winds are too high for me to shut down and the size of the heliport doesen’t always allow me to park directly into the wind. The propellors in this design provide yaw control and sometimes I have to keep the rotor rpm at full throttle to insure I have full tail rotor authority and I can keep the aircraft from weather vaning into the wind. I’m all for research but I don’t see this design as being practical.

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