One thing which horrified me, when I spent a season in ( clapped out ) Cessna 172's; one day we were trundling, straight and level, when the artificial horizon keeled over.
The senior ( and aerobatic trained ) CPL remarked as if it was nothing, " I see the vacuum's failed " but it struck me as damn dangerous, especially for inexperienced pilots caught out in IFR; am I right in thinking that in something like say, a Hawk, an 'inop' red signal would have come up over the instrument ?
I do know several Sea Harrier pilots were said to have been killed on attempting vertical landing ( source- another Sea Harrier Test Pilot, not J.F. ) when following their artificial horizon at night & the gyro's toppled, leading into a steep bank & crash into the sea.
Mind you, that pilot liked the Harrier, but wouldn't step into any aircraft, light G.A. or Military, unless a lot of £ signs flashed before him.