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Old 9th Apr 2012, 14:31
  #75 (permalink)  
jeffg
 
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JD,

40/800 has been in the UH/AH for a very long time, well before the V-22. It's also in the H-57 manual so every Naval Aviator should be familiar with it. I also believe but can not confirm that it is in the CH-46 manual.

I know its not in the 53 NATOPS. I know this because the morning after Marana our 53 project pilot at NRWATS came over to our section asking what this '40kt 800 fpm rule was'. He was surprised there was such a thing and we were equally surprised he didn't know about it. A difference between communities.
While it may not be in the RFMs I know the Navy, Army and FAA teach different versions of this rule as basic piloting technique.

SAS
"One does not turn into a Frog at 800fpm ROD and 40Kts IAS.....there is far more to it."
True. In fact the V-22 won't encounter VRS roll off at 40 its until at 3000 fpm ROD, at 15kts it will be about 2000 fpm. But it's different for every helicopter. Heavier disk loading equals less susceptibility to VRS, therefore JDs experience in the 53 doesn't surprise me wrt having a hard time finding it and maybe that's why it's not in the Sikorsky manuals? I believe 40/800 is a rule of thumb taken from early VRS testing done well over 40 years ago. That data showed that a single rotor system could get into VRS at less than 800 fpm ROD.
By the way, staying within the limits of 40/800 you can shoot up to a 15 degree glide slope approach.
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