Helmetfire: Have a quick look yourself for the technical minutae as it is a nightmare wading thru the tech spec. If you still want clarification get back to me and I'll dig the stuff out.
Bottom line in the UK is that the goggle tubes MUST NOT have the ability to fail simultaneously. i.e. they must be sourced by separate power supplies.
Reference is: DO-275, MOPS.
DO 275
Type that into Google and good luck!!!
