you fly a 4-engine airframe around on two engines to conduct the research, and leave two engines for standby just in case
Ya mean ... Nimrod?
Surely a few of those old relics could be scared up into the air?
The damned things are little better than scrap, worth rather less actually 'cos they'll have to be broken up into small enough chunks to toss into the melting pot.
A few trips round the North Sea might make the old dinosaurs live again, if only for a week or so. So what if the engines become tired and shagged out after such a squawk?
It's far too good an idea to be taken up by their Airships in Main Building though.