Errm,
sorry - but I logged Mar 24 1993 XV 227 40 minutes day, RTB Rib 2 overheat, and I can vaguely recall at least one more... and my flying hour count is impressive for a Tornado pilot but barely gets me through the door of a maritime reunion, so an airborne Rib 2 wasn't common, but I suspect I'm not the only kipper guy on here who thinks the line about most folk having experienced one or two in their time is accurate.
Memory is hazy, but a rib 2 O/H - whilst being a fire warning and therefore taken seriously - usually didn't turn out to be an engine fire when investigated, as I recall? I do seem to remember that on that day in 93 I was reasonably calm and thinking 'this'll turn out to be the fire wire having a senior moment'... though as a siggie I did believe in the power of seaweed, chicken bones, and knew far too little about a/c systems, I will admit.
Rib 2 was definitely not a DSS only experience.
I am more than happy to defer to Kev on the technical side, of course, as he's not exactly a beginner as far as Nimrod systems go.
You piloty type people would be mighily warmed by the faith we down the back used to have in you*, even those piloty people who made it through Biggin on the strength of a PE degree.... (THAT, however, is another story, isn't it Co? <g>)
Dave
* Mind you, for anything serious, we were usually more happy about the fact our eng's were enlisted scum with scabby knuckles.