It could be they have actually modelled the conditions for VRS more accurately than we usually experience.
You need three conditions for VRS to be possible.
- Airspeed lower than effective translational lift.
- Decent rate greater than 300 feet per minute.
- 20-100% of available power applied.
And yes I did have to remind myself of these conditions.
There are a great series of explanations on YouTube covering various aspects of helicopter flight. Well worth a watch, search for Helicopter lessons in 10 minutes or less. ![]()