The increase in torque during a roll was very noticeable on the Gazelle and was explained as follows. During a roll to the right (towards the advancing side) the blades on the right flapped down and experienced an increase in AoA – the blades on the left flapped up and their AoA reduced. Th advancing blades have high AoA and high speed the retreating blades have lower AoA and speed and the overall result is an increase in rotor drag. Rolling to the left produced an opposite effect ie torque reduction. The torque spikes were only evident as the roll rate was increasing, once it reached steady state there was no appreciable difference from the S&L flt torque.
The Gazelle has a fixed spool engine with reset governor – it maintains a constant Nr with no static and minimal transient droop which may account for it’s sensitivity to changes in rotor drag.
Of course the Bell will have rotors turning the other way which does not explain the torque increase in a climbing right turn.
Over to you Shaun and Nick….