Is it still legal in F1A/F1H/Classic to use a tow rudder attached to the tow line that falls away with the tow line as it is released from the model?
Naturally this tow rudder, in addition to counteracting pre-set on-board glide turn, can be used to increase rudder area significantly during straight tow (and help keep model pointed into the wind?).
I do not think any of the towline glider classes specify min/max area of any vertical surfaces.
Would it count as a part falling off nowadays?
Have not seen one used for years and years. Understandable with the A/R and circle towing in F1A/F1H, but, Classic could benefit.
A part cannot fall off the model in the FAI classes, but you certainly can have an auto rudder that is activated by the towline coming off. That is common practice with straight tow models. It might be ok if it fell off before the flight started, i.e. before the model came of the line but that seems like a risky proposition.