Not sure about the rotorway but the Cobra pitches nose up in engine failures above 120 knots.
I vaguely remember it had to do with the rotor system at that moment producing more drag then the fuselage and the effect of the horizontal stabilizer at speed.
The problem it caused was that if you did not input a cyclic movement (actuating the flight control side of the stability system) the system would think the pitch up was an external force and attempt to compensate.
Rapidly driving the disc forward
While the nose was coming up
