Originally Posted by TwinHueyMan
(Post 10239701)
Those temp/PA combos equal out to 14k+ DA, which is the limit for any operations.
Mike The R44 NO FLIGHT area checks out ok with everything being at or above 14,000 DA, but the R66 chart does not at 6,000' or 8,000' PA and 40 degrees where NO FLIGHT is below 14,000' DA. |
I stand corrected... There's also a limit on closing the throttle above 10k DA "to prevent engine flameout", and an ISA+35c / 50c temp limit in section 2 of the POH.
Mike |
S/n 1000 delivered
So many congratulations And celebrations to Robinson on this milestone..
https://robinsonheli.com/news/robins...l-number-1000/ Cheers |
An amazing achievement indeed. I fly the 66 regularly and as an all round practical personal helicopter nothing beats it.
Well done Kurt & Team. CRAN |
New tail
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Originally Posted by bellblade2014
(Post 11507203)
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: https://d3lcr32v2pp4l1.cloudfront.ne...-505_62117.jpg 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: https://cimg0.ibsrv.net/gimg/pprune....42f19e79f0.jpg 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. |
The mounting of the Bell 505 stab is significantly cheaper than the special type of welding that would have been required to integrate it into the tailboom.
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Originally Posted by helispotter
(Post 11592923)
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?
The proof that nobody has understood anything is all these new horizontal stabilizer evolutions/modification, the H160 being a visible effort in that field. The R66 just got it from the R44 that got it from the R22, I think you would be chocked to see how little thought went into it. |
Originally Posted by Agile
(Post 11593366)
I have doubts that anybody understand the flow pattern on the tail of a rotorcraft. You got the induced flow from the main rotor, possibly the interacting flow from the tail rotor, and then the forward air flow. That sounds like a big whirlwind shake to me, Hills and the HX50 treat it with aerodynamics principle akin to a high performance glider, well I don't buy it. last time I heard, CFD on a rotor system is still a developing science due to the complexity of the flow interaction between blades (tip vortices) all that in a moving frame of reference.
The proof that nobody has understood anything is all these new horizontal stabilizer evolutions/modification, the H160 being a visible effort in that field. The R66 just got it from the R44 that got it from the R22, I think you would be chocked to see how little thought went into it. As for H160 'bi-plane' horizontal stabilizer, my initial impression is that it is somewhat marketing gimmickry. But then again, there may be structural or other motivations we haven't grasped, for example: https://www.geekwire.com/2023/boeing...ient-airplane/ Regarding the Hill use of fences on their stabilizers, I will bring that discussion over to the HX50 thread (with more details and link to video) as I am really quite interested to hear more about that feature, but so far I share your sentiment on this too. |
Originally Posted by helispotter
(Post 11592923)
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. 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. |
Originally Posted by PhlyingGuy
(Post 11593012)
The mounting of the Bell 505 stab is significantly cheaper than the special type of welding that would have been required to integrate it into the tailboom.
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Originally Posted by helispotter
(Post 11593414)
least two universities in the USA that have more complex rotorcraft aerodynamics CFD analysis software in use that handle transient aerodynamic problems. Those may be standard CFD suites tailored to helicopter aerodynamics problems
(Head of R&D at airbus helicopter is from that Maryland Campus) Georgia Tech has a nice Video about the state of the art in helicopter CFD, check 25 minute mark to start to feel how involved it is and 54+ minute mark to see how messy it is on the tail. 14,000 compute hour per simulation run !!! ouch, cloud computing bill must be hot. |
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