Originally Posted by
barit1
Droop governing is characteristic of most turboshafts pre-1970. It's relatively easy to implement with hydromechanical controls of that era, and has the advantage of giving a fairly crude means of load sharing in multi-engine choppers.
A few engines had "droop compensation" - wherein the droop line was mechanically "nudged" through a link to the collective stick. (Pull more collective, and the droop line is repositioned to hold constant rpm.) GE's T64 in the H-53 series is an example.
For true isochronous governing, electronic controls (either analogue or FADEC) have been the only practical solution.
Transient droop can also be largely overcome with electronics - the black box senses the rate of collective movement, and applies power to attempt to "get ahead of" the load demand.
Hi barit1, I'm still struggling with this concept. When you say it's "relatively easy to implement"; How is this done? Looking at the internals of the B206 governor, I simply don't understand why it doesn't return to the previous RPM. (ignore the compensation for a minute). In my mind, after a load change, the PTG will let the FCU accelerate N1 until the PTG thrust bearing is back in the prior position. How can this happen at a lower RPM if the speeder spring hasn't change. Tearing my hair out!