Fuel transfer

I was wondering if it was possible to transfer fuel from a full external tank into the jet with the internals and the reservoirs completely drained? Or would you have to completely refuel then defuel?

Why are the externals full if the internals are empty?

I was wondering if it was possible to transfer fuel from a full external tank into the jet with the internals and the reservoirs completely drained? Or would you have to completely refuel then defuel?

IIRC, you can. Best way is to lock the externals, build the pressure to the correct amount. Once they are pressurize, open the externals and keep an eye on fuel transfer. Obviously I'm talking about using eternal power and MC-7. It will take a bit longer with -60 to pressurize the fuel system. I think the external tank T.O. transfer check has this.I can't remember the number anymore: is it 28jg-10-1?

You would need fuel in the reservoirs to get the wing pumps spinning. Only way to get the fuel out of the wings since the centerline tank feeds to the wings. Since there is air in the fwd and aft tanks the siphon system is in hydraulic lock.

MVSGas is right if we have external tanks installed we will leave them full and locked out. Then defuel the internal and do our fuel cell work. Then transfer the fuel out of the tanks to check for leaks.