Question about fuel pumps on startup.

[Aernov]

Is MiG-21 supposed to start and run it's engine with fuel pump switches off? Real procedure requires (or advises?) at least feed tank pump on before engaging starter, with enabling two other pump switches soon after engine idle RPM stabilization and AC generator becoming operational, in DCS engine can start and operate with all pumps off.

[Dr_Arrow]

Yes it is possible, I know even a story of a student performing one of his first solo flights with fuel pumps disengaged, where he wondered why the empty tanks lights were blinking during pattern flight in turns even though the fuel tanks were full. Only after landing he realized that fuel pumps were off when switching the engine off. It wasn't however Bis version, but the fuel system is nearly the same.

[Aernov]

So, what is the purpose of these pumps? Just prevention of immediate shutdown at near-zero or negative Gs?

[unknown]

16 hours ago, Aernov said:

Is MiG-21 supposed to start and run it's engine with fuel pump switches off?

I'm no Mig-21 expert, it's been a while since i read the manuals, but from what i remember the fuel pumps are "just" used to manage correct fuel flow from the tanks to the engine in situations gravity is not enough. From the Mig-21bis flight operations instruction, you turn on the fuel pumps after engine start:

 

[Frederf]

Engine pulls fuel by mechanical pump. Switches are for electrical pumps. Officially I think supposed to run dispenser tank during start and add rest later. It might vary with without external power. In DCS battery power can run out but never an issue running all 3 anyway.