Stilton, look at a photo of a Chook - the blades intermesh and are very unlikely to bump into each other. There is fore-aft movement available.
SASless, there was an interesting accident in Oz back in 75 or 76, the right engine turbine blew out, went through the centre pylon and lodged in the left engine. Along the way it cut through hydraulic and electrical lines. The Chook was carrying 3 bladders of water on a training run, and the pilots tried to pickle the load, being under severe OEI conditions.
But with no electrics, could not pickle load. Loadmaster tried to move through the cabin to do manual release, but slipped over in the gushing hydraulic fluid. Machine could not hold height, and they did a running landing on a flat field - the squishing of the water bladders was a lot more convenient in cushioning the impact than landing on the big truck they normally used.
On rundown, with no electrics, they could not use the sped trim to level the rotors, so the back rotor started to slice through the transmission tunnel and fuselage as it slowed down.