Originally Posted by
SASless
Meanwhile.....Sasless mouthing spit bubbles sagely nods in agreement.
That is due to a couple of lines of that post by Baldeep Inminj.....
One will note that no colored pencils were harmed in the creation of that explanation.
Well done BI!
SASless and JohnDixson were both involved in UH60 test, and I would imagine that the only two items that would be of concern in that video is the rapid longitudinal cyclic application at low speed which leads to reduced TPP/tail clearance, but was still within limits... and the possible pitch link loads during what is nearly the UTTAS RTT manoeuvre, which IIRC is still not within the design limits of the UH60 when performed to the original specs. The stall of the blade in high speed flight is almost always a retreating blade event, with predictable consequences. Doing that from an underspeeding NR could end badly, as in doing the 1.1 max autorotation at min Nr in autorotation, in a left turn and recovering with a pitch up before adding torque. (that test point gives very high root bending loads and pitch link loads as well, and the vibration in my experience is pretty close to the edge of fun.
Wayne Johnson wrote the NASA TM 81182/ USAAVRADCOM TR-80-A5 Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics, which is more or less the basis of his later theory manuals, but it has the equations in there handwritten, which is quite a piece of art, whether we follow his maths or not, it is good. It is also free... around p97 the conversation, and it is that, gets to aerodynamic analysis, and that runs for 30 pages. The late sections add the inertial and aerodynamic effects are good reading, as is every bit on stability and control. I need coffee when I read his stuff, and then aspirin afterwards, but there is a lot of hidden gems in those pages.
All up, keeping Nr in the normal region for the operation is desirable. Like every part on a helicopter, limitations are there for good reasons.
Johnson -, W. (1980). A Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics Part 1: Analysis Development.