We operate a fleet of 350 BBs with throttles on the collective.. We do not simulate governor failures by reducing Nr below the governed band because the RFM Limitations section only allows Nr at 390 +/- 4. To practice a governor run down/fluctuations would required the Nr to be reduced below the minimum governed. However, I know that the Australian military used to ignore this and use the throttle to practice gov probs and tail rotor malfunctions.