Apologies, this question is directed at other 747-400 users, hence the title.
The minimum manoeuvre speeds associated with various flap settings are referenced to margins above VREF30 e.g. the Flap UP bug speed is VREF30+80.
On departure, VREF30 is the same as (or as near as makes no difference) to V2 and as such V2 is used as the reference to which additions are made (if operating non VNAV or Speed Intervening). This is because V2 is readily available through the FMC and is already dialled up on the MCP.
I am merely interested to know why it is that V2 and VREF30 are so very similar. Is it just a massive cosmic coincidence especially given that V2 applies at take off with Flap 20 and VREF30 is for landing with Flap 30?
I suspect it's down to the margins above Vmca that must be attained for a minimum V2 and a minimum Vref....