Originally Posted by
tascats
The Saab 340 prop straps would often be broken after gusty winds when parked for a while - the canvas part with the metal ring (which looks like the part in the above photo) would be left attached near the root of the blade and quite hard to spot on a dark morning or if the prop had rotated to the 12 o' clock position. The remaining two clips would still be attached to underside of the intake but the prop could rotate freely. The canvas piece was quite tight on the blade sometimes so could easily have stayed on for a period before being thrown free.
It's the left hand prop strap which is in place during boarding for most operators. It holds the barrier strap to stop passengers walking between prop and stairs. So very unlikely it was broken pre-flight. In anycase proper pre flight inspection of any turboprop requires a close, thorough look at each blade and its condition. That would easily find a rogue propstrap.
I've heard of quite a few propstraps being left on for start over the years. Never heard one that stayed on until take off, let alone penetrate the cabin. Always a first time for everything I suppose.