On the 747 classic the manifold is to be pressurized in all critical phases of flight.
For instance on take off you would use the classic H pattern.
For landing one of these crossfeeds would be open to accomplish this.
Some airlines even go back to the H pattern to insure this.
Depends on your company procedures.
For instance on the 747 classic.
Fuel managment.
Set for landing,
Check all main tank fuel boost pump switches to on.
All main tank boost pump low press lights extingueshed.
Check No. 2 fuel crossfeed switch in the open position.
No 1,3,4 crossfeed switches in the closed position and all crossfeed lights extingushed.
Check your company SOPS.
As this may be different, but in all cases the manifold should be pressurized for T/O and landing.