Ohio - EMS BK-117 accident video - no injuries
 

No one knew about the fence being there and it was obscured by tall grass. Is all grass usually kept quite low at airfields to avoid this kind of problem?

Nasty surprise.
Well handled, resulting in no injuries!

Thats something you would not be expecting! It reminded me of a snake striking.

FOD rather than a fence, I think.

In the US we call that "silt fence". It is used on construction sites for a variety of erosion control purposes, and indeed the Youtube video description reads "As the helicopter began to take off following the hover, it traversed a grassy area adjacent to the ramp about 10 ft above ground level, where a silt construction fence was obscured by tall grass. As the helicopter overflew the fence, it became unsecured, blowing up and into the helicopter’s main and tail rotor system."

I wasn't there, obviously, but I'm betting it was clearly visible to the pilots and not at all "obscured by tall grass". It looked like it was protecting against erosion along the edge of the construction area, which is not unusual at all. Sometimes it is placed vertically on stakes. Other times it is stapled down to the ground with long turf or ground staples. Sometimes it is held down with sandbags.

That said, an easy thing to overlook, particularly if you had already overflown it without incident.

Scary stuff!

Might think about hover taxiing over paved areas when operating from facilities in the future. Blowing over somebody's Cessna would be far less expensive than trashing your whole helicopter powertrain.

What is involved in examining the aircraft to check for structural damage?



mjb

Inspect just about everything - door fits out of whack means fuselage deformation, if the belly has touched the ground (which appears so as it is sitting on it) assumption is more than 10 g and engine removal and inspection required.
The list is much longer of course but those are the items which may make it BER.