Since the rotor and propellers are driven by the single gearbox, starting the No. 1 engine begins all three turning simultaneously. The No. 2 engine is then brought on line as in any twin-engined aircraft. Conversely, on shutdown, stopping the rotor with the rotor brake simultaneously stops the two propellers.
I was flying with Eurocopter test pilot Herve Jammayrac, who I had flown with eight years earlier for a pilot report on the EC225. Since this is not a production aircraft, we spent virtually no time on specifications such as payload weight limitations or power settings in various flight modes. Of key interest were propeller pitch settings and speeds at various stages of flight, as well as rotor rpm readings. I was also interested in torque readings, since the transmission can be a limiting factor.
Jammayrac says that, in a production H3, standard rotor speed will be about 340 rpm, dropping to about 310 rpm at higher airspeeds as lift shifts to the wing. For ease of manufacture, the X3's rotor speed is fixed at 310 rpm.
Pitch of the propeller blades is set by the throttle control lever (TCL), a “coolie hat” toggle switch on the collective-grip control box. A much larger back-up throttle, similar to fixed-wing engine power levers, is located on the center console, but not generally used, Jammayrac says. Only a slight thumb movement on the TCL is needed to either increase or decrease prop pitch.
When we were cleared to taxi from Eurocopter's helipad out to the Grand Prairie Municipal Airport, Jammayrac simply released the brakes and applied minimum pressure to the “coolie hat” to get us rolling along the taxiway, “driving” the X3 like a prop-powered fixed-wing aircraft.
Once outside the company area, Jammayrac brought the X3 to about a 5-ft. hover, with both engines producing a combined 48% torque on a 93F day. Hovering the X3 is the same as in any helicopter, just a matter of being steady on the controls. Low-speed flight seemed perfectly normal, both forward and sideward.
Winds were gusting around 18 kt., but seemed to have little impact on the hover. One difference from a helicopter is that without a tail rotor, there is no loss of tail-rotor authority in winds. In helicopter mode, using rotor cyclic instead of prop pitch to accelerate, the X3 would stay below 80 kt. as the propellers act as aero brakes.
Once established in a stable hover, takeoff is accomplished by simply pushing forward on the TCL toggle switch. As propeller pitch and aircraft speed increase, rotor pitch decreases and more power is directed to the propellers, to the point where the X3 is basically a fixed-wing aircraft taking off 5 ft. above the runway.
The aircraft maintains a level attitude, with no dropping of the nose. But Jammayrac pointed out that by using rotor cyclic control, combined with prop pitch, you can take off with a nose-low, -level or -high attitude, depending on your preference.
If there was any translational lift as we moved from hover to forward flight, I did not notice it. The aircraft just started climbing. Our takeoff was done with roughly 29-31% torque, then we climbed up to about 2,000 ft. at 110 kt. at 27% torque.