Originally Posted by
bellblade2014
bellblade2014: I see nobody had so far given any feedback to your question from last September. I certainly can't comment as a non-pilot, but that Vertical Magazine article sure seems quite comprehensive in its coverage of the re-design of the R66 tail surfaces. Of course the test pilots at Robinson Helicopters would presumably be able to respond in detail.
I came across your question while checking if this modification had already been the subject of discussion on PPRuNe as I only just read about it now also becoming available on new R44's with option to retrofit existing R44's, see:
https://www.flyingmag.com/new-robins...ennage-design/
I hadn't been aware it was already being fitted to the R66 until reading that article.
This is where it gets interesting: During initial flight testing, the Bell 505 Jet Ranger X originally had a tail surface configuration which seemed quite similar to the R22, R44 and R66 in that it had a horizontal stabilizer projecting only to one side of the vertical stabilizer. The vertical stabilizer looked similar in overall shape to that on the original Jet Ranger. See image below found on web:
However at a later stage of flight testing and for production, the horizontal stabilizer was removed and a larger symmetrical (left and right) stabilizer was 'strapped' below the tail boom:
This brought the 505 back to a tail configuration much more similar to its Bell 206 predecessor, though the horizontal stabilizer now looks like an after-thought rather than its integrated form on the Bell 206 where the stabilizer effectively 'passed' through the tail boom. I am sure this comes at a price of additional interference drag compared to the 206 implementation. There is some old discussion on one Rotorheads thread about the horizontal stabilizer implementation on the Bell 505 in which the need for the larger 206 stabilizer had already been anticipated by one writer.
So while some tail elements of the 505 may have originally been modelled off the Robinson, in the meantime the Robinson now has elements off the current 505 tail! Perhaps all helicopter designers should first look to the 206 for inspiration!
Also interesting to note the Hughes 500, having started life as the competitor to what became the Jet Ranger, originally had an asymmetric V-type vertical and horizontal stabiliser combination (in the 500C). But the design later changed to a T-tail configuration in the 500D. Perhaps Hughes realised the benefit of a symmetrically arranged horizontal stabilizer as well?
A final observation: In one of the Hill Helicopters videos on the HX50, Jason Hill makes mention of the use of what I would call a 'fence' fitted to the horizontal stabilizer just outboard of the tail boom and indicates this is all about improvement of the flow characteristics over the stabilizer (or words to that effect). It seems complicated to me, but I haven't seen the CFD analysis they have no doubt undertaken to come up with this detail. Still, it is surely a less draggy stabilizer implementation than what is now on Bell 505, R44 and R66?
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.