Good question, it would depend on how much fuel was in the tank.
You don’t gain anything in the way of ancillary systems by keeping the engine running though, you still have the increased fuel burn of being one engine inop (approx +10% per failed engine) plus the fuel burn of an engine at idle. The associated hyd system doesn’t need the engine, there’s a back up demand pump on all four systems that takes over if the engine driven pump fails (the 744 has ten hyd pumps, four engine driven, four back up and two for ground use). Having four generators is no different to having three, there’s no load shedding, having four bleeds is no different to having three. Even if you can’t restart it one engine inop makes no difference to the approach capability, it’s CAT3B no DH either way. There’s no oil lubrication issue with a windmilling engine with RR engines. It’ll fly just fine two engine inop even with both out on the same side, it just becomes Cat 1 only with reduced GA climb performance (IIRC approx 1000agl is the lowest you can GA 2EI) and really high MSA’s are an issue which is why both issues are assessed among other things as part of the continuation policy.
I think I’ve just talked myself out of keeping it running!
Last edited by Locked door; 20th Nov 2021 at 12:15.