I've just paid my annual visit to Stavanger's Sk61 simulator, to revalidate my rating, training all those Cat A take off and landings. While studing cat a procedures, one question came into my head. Most helicopters that i've flown use similar Nr droop on these procedures, of about 91-94% Nr. These similar numbers, plus sentences as "use collective to droop Nr to a minimum of 91%" or " with light helicopter it can be necessary to increase colective to droop Nr" (similar sentences can be found on AW139 manuals), make me ask some questions about this RPM droop. Is this Nr number of about 91-94% a limit not to overstep, or is a value where blades, engines or whatever offers its maximum performance??; This Nr droop is something that happens from the OEI flight condition, but as conclusion of sentences before, is this Nr droop a value that we need to find, raising collective if Nr doesn't droop??.
So, if anyone knows anything about this, some technical data, aerodynamic information, please, i'd like to know how it works.
Thanks!!!
