Not really a mistake as such but a 1 in a million
I was flying a Seneca Five twin from the South of England up to Inverness.
I knew there was a line of storms running West to East right across the top of Scotland Hence I needed to stay visual to find a way through and down into Inverness.
I had been pushed up by a rising solid deck of cloud and took a climb in IMC to FL 130.
During that climb I picked up a lot of ice used the boots and was then clear on top but with one engine feeling lumpy.
There was a bang and a large piece of ice flew almost straight forward crossing the nose and came back hitting the prop on the other side.
This slightly bent the tip.
The props are counter rotating and that prop threw the ice into the side of the nose puncturing a 2 in break in the skin.
The ice then came back and hit the Screen where thankfully it went into a snow shower.
I found a gap in the CBs ahead near Aberdeen and descended through there landing at Inverness where they had had hailstones the size of marbles.
There were three wires which went to the props on the pilot side these had rubbed through on the nose and had cut meaning no prop deice on that side.
I checked the satellite pictures and out over the Scottish islands was clear so I elected to take the aircraft back low level down Loch Ness out over the islands down past the IOM.
But 1 in a million chance
Pace