Flying Scotsman

I’m a tad confused here. AFAIK, 60103 is an air braked loco but can create vacuum. If it couldn’t it wouldn’t be much use on most heritage railways which only have vacuum fitted stock. It certainly couldn’t do anything on its forthcoming visit to the NYMR. As such it must be fitted with an air/vac proportional valve. Based on this supposition there should be no need for a diesel to act as a brake translator loco. If the train is air braked it just runs on air. If the train is vac braked it requires both vac and air operational but that is possible with the existing set up. It was certainly the case when it was at the NYMR a few years ago.
A diesel certainly can’t act as a brake translator if it is at the rear of the train.

 

All I can add is that that the time of working with a "translator" loco 60103 was air-brake only as its vacuum brake hadn't been fitted. Interestingly on SVR visits any air-brake only diesel loco is paired with a "translator" locomotive to allow its working with vacuum- brake stock for - presumably - the same technical reason. In all cases the "translator" loco is always next to / immediately behind the train engine.

 

For a while, after 60163 had been converted to air braking of the loco and tender themselves, its erstwhile Chief Engineer refused to fit a vacuum brake ejector, because he did not want the loco to operate on preserved railways. At the time not many preserved railways had dual braked or air braked stock.
The vacuum ejector etc was eventually fitted.