"Ice Chunk" cracks & obscures PC-12 windshield at 15,000 feet
 

SeaPort Airlines flight from PDX to SEA (Pilatus PC-12 with six passengers) Friday evening, Jan 8, reported the captains windshield cracked with no forward visibility for left hand seat. AC was was at 15,000 feet on descent to SEA when incident occurred. Pilot in RH seat made a non-emergency landing at SeaTac.

Video shows entire left side of windscreen covered with cracks.

Multiple press reports (there is an active and knowledgeable aviation press corps in Seattle) is reporting damage was caused by an "ice chunk" that struck windscreen.

Where did such an "ice chunk" come from? There was no reported convection in the area.

If it came off the nose of the AC - how did it have enough relative velocity to damage the windscreen?

Are "ice chunks" into the windscreen a common problem?

Video and passenger interviews at KOMO TV, KIRO TV, KING TV

PC-12 has a single engine with prop on the nose. I'd expect prop ice to be thrown sideways - but if it came from near the hub, or on the spinner itself, the centripetal acceleration would be lower than from the tips, and it might stay in the prop wash and slipstream blowing straight at the windscreen for the fraction of a second needed to travel the 6 feet.

I'll leave it to PC-12 drivers to comment on the probability.

An ice chunk could fall from another aircraft at a higher altitude - environmental icing or the classic "blue ice" from the toilet drains.

I might that while I have never had an aircraft windscreen broken by anything - I have had two car windows cracked by debris falling off vehicles ahead of me traveling at the "same relative velocity". Once something falls off a moving vehicle and is no longer powered, it tends to decelerate (accelerate backwards) pretty rapidly to the local air velocity. Add in a push from the propwash....

Were the windshield heaters on if they have them installed

This would be as likely as the "Joe Dirt" phenomenon...:D

I have had two broken windows in 737s - the glass shatters, the perspex laminate is unaffected, and maintains pressure. Both were caused by window heat element arcing and I would assume the same happened here. The "ice chunk" report, although possible, will most probably be an error by either reporter or pilot. Even a bird strike would be more likely.

What about prop or spinner?

How do they know it was ice, I have had 5 windscreens crack on me over the years none of them due to ice but an overheat controller.