Originally Posted by
helispotter
If David Smith reads this post, I would be interested in hearing his take on the topic if he is open to speak about it. From the Vertical Magazine article, I guess he has more experience than most on this subject now.
I had comparatively little to do with the recent Robinson tail as I joined the company well after the project started in earnest. I just helped to share the background in the article you linked and the associated podcast. It’s a very good story of modern tools helping to improve understanding of a very complex phenomenon. The industry’s understanding for decades has been incomplete regarding the primary contributors to the rolling moment of helicopters during low-g flight. Now we have a much more complete picture of the aerodynamic factors and a way to reduce the rolling phenomenon. That is what drove the new Robinson tail. Please avoid low G flight! No matter what tail you have low G flight can be hazardous with a teetering rotor.
The 505 change was made for an entirely different reason related to the stability of the aircraft in hover and the pitching moment of the aircraft as it transitions from high to low speed and low to high speed. it turns out that the horizontal stabilizer, when it is located inside the hover downwash like on the 505, offers a helpful stabilizing effect to make the aircraft easier to control. It was hard to tease this out during the testing but had nothing to do with low G roll. I imagine if the 505 had not made the change early in the program, it might have seen similar roll moments in low-G.
I hope this helps. Feel free to message if you are curious about this topic.