Following a training flight on the trusty old Whirlwind 7, my instructor and I noticed oil dripping gently from the engine compartment. When we opened the clamshells we discovered that one of the upper cylinders (Leonides Major, double banked 14 cylinder radial) was missing - piston, con-rod, the lot. We hadn't noticed a thing during the flight!
And, there was so much inertia in the head, you could fly the thing virtually straight and level, albeit briefly, in autorotation. No need to flare at the bottom, just come down at (I seem to remember) 40 kts, haul in some lever and fly it onto the ground.
They don't make 'em like that anymore.