He had a wind from the right which helps in a right power pedal aircraft. = stable so far
It is correct that in a CW rotating helicopter, wind from the right 'unloads' the anti-torque device. In other words, the wind pushes in the same direction as the tail rotor thrust vector. Stable so far, OK, but for how long?
When I did my type conversion on one of those French Fenestron-equipped helicopters, I was taught the that there is a specific problem with wind from the right, related to the
stalling of the vertical fin:
- A large portion of the anti-torque thrust of a Fenestron comes from the airfoil profile of the vertical stabiliser = at forward speed the tail fin creates lift supporting the Fenestron.
- That tail fin stalls at a given given speed and Angle of Attack, like any other wing.
- While wind from the right initially supports the Fenestron (ie, requiring less right pedal), the same wind from the right increases the AoA of the relative wind. The increased AoA makes the tail fin stall earlier (at higher ground speed).
- The change of right pedal required (from pre-stall pedal position, to the position required post stall) is more dramatic in this scenario, as due to the right wind initially the right pedal required was lower compared to pointing straight into wind.
It was said that many pilots got caught out this way. The convex training put specific emphasis on sensitising new pilots for this specific "gotcha" scenario.