Chinook
Tandemrotor. As quoted in the book Chinook Crash, at the FAI Holbrook said that they (ie he and his companion) could see the lighhouse's white perimeter wall, but above it low cloud obscured the hillside. And later, ...he could clearly see the Mull and identify the lighthouse as a lighter patch, but low cloud still hung over the upper part of the Mull.
You may be interested to read the several descriptions of the weather by the ten or so folk who were on the hillside at the time; they are on pages 15-19 of the book. They all talk about the fog in the area, and the visibility is variously described as 10-15 feet and 20 yards.
With all good wishes. JP