332L double eng failure
This was in the second or third winter of operation, so around 1984. The engine intakes are protected by the "chip baskets" and the engines themselves have hot oil circulating inside the inlets, keeping them warm in icing conditions. But no consideration was given to the 9" or so of ducting between the two. Ice built up in this ducting at around zero C in very moist conditions, then a slight increase in temperature caused the ice to break away in a oner, putting the fires out. The fix was to add electrical heating mats to the ducting. Simples, but the original omission was a classic case of trouble in the bit where airframe manufacturer meets engine manufacturer.