2. the airplane
will never reach 260 kts until 400 ft, where, presupposing VNAV was
armed, VNAV SPD kicks in as a pitch mode which will replace the previous command speed as we know, THEN definetely commanding V2+10 to V2+25."
True... I suppose we are into hypotheticals here... What if... VNAV was not armed?... What if... the FMC was inoperative?
Some are under the impression that the V2 reference for the FD (even below 400') is coming from the FMC, not the MCP. United Airlines, I hear, dial in V2+10 in their MCP. If the V2 ref is coming from the FMC, then your PFD CAB would be at V2+10 (from the MCP) and your FD guidance would give you V2+10 also (from the FMC). A neat "matching" solution. Personally, though, I don't think the FD would give you V2+10... I think it would give you V2+10+10.
"What was the speed he actually got before passing 400´?"
I'll have to get back to you on this one. I'm not sure if he armed VNAV.
It's something which is difficult to check, even in a sim. You'd have to nail the airspeed at rotation and follow the FD bars religiously, to see what speed resulted. I'm hoping someone from United is reading this thread
Cheers.
NSEU