Part of the reply from 'CRAN'
Small helicopters such as R44, B206, EC120 have control loads that are light engough that should the hydraulic system failure the pilot is physically stong enough to move the controls manually. i.e. Manual Reversion. In bigger machines such as the Squirrel/AStar the loads become too large and the pilot simply wouldn't be able to move the controls.
'bigger machines?' the squirrel? You've obviously never flown the ubiquitous UH-1, which was quite benign following a failure of the one hydraulic system, and had a MAUW of 9500lb, although the fact that it was a teetering head probably helped. Mind you, if you kept it airborne for too long your right arm used to start vibrating!
But at least the collective was assisted by the tension/torsion straps.
It wasn't until Bell came to their 'bigger machines' that they gave you the luxury of two 'highbollock' systems!
'up the banner' - oops, given the game away to some!