Brian, if we are to have any meaningful discussion we need to ensure that we are clear about what we mean by the words that we use. It also helps if we take into account the context of that discussion.
Earlier in this thread Silvo said
"
AFAIK, one advantage of the twin spool (if this is what you mean) engine is that you dont need a clutch system on helicopters fitted with this kind of engine."
Wobble2plank then said
"The fixed turbine does as Silvio says need a clutch system which complicates things slightly."
From these comments it should be clear to us all that they are not talking about a freewheel unit. What they are talking about is a device whereby the fixed turbine engine can be disconnected from the rotors in order to allow the engine to be started without starting the rotors. Then either manually or automatically the two are connecetd together.
In this context a freewheel unit, be it Sprag type or not, is not the type of clutch that is being discussed.
As for your challenge to me to name a a helicopter that does have the type of clutch to which I refer, I do not need to do this because Shytorque has already done so when he said "
The Gazelle, which is equipped with a coupled turbine, has a ramp and roller freewheel and a centrifugal clutch. The engine can be run at idle (25,500 rpm) with the clutch naturally disengaged. As the throttle is advanced the shoes move outwards and engage the transmission, turning the rotors. The pilot had to monitor the speed at which engagement took place, it it was too reluctant it meant that new clutch shoes were needed. "
It is worth noting that this helicopter has both a "ramp and roller freewheel" and also a centrifugal clutch.