There is a multitude of MTOW (structural) depending on how much you paid for. At 75.0T it is 221kts on NG-800
Yes, and at higher MTOW it gets closer to 230kts. Ours are 79.0T and it's 224kts. I'm just throwing in another theory that was suggested to me once upon a time... Plausible, but with no more authority than any other theory I've heard.
Some suggest that it's due to a LED limitation of 235kts. That is not published in my manuals. The LED limitation is obviously 250kts for flap settings up to 5 (and alternate flap extension is irrelevent to this discussion).
However, up to flaps 5, the LEDs are not fully deployed. Boeing permits up to flaps 25 for take-off. In non-SFP variants, the LEDs are fully deployed at take-off with flaps 15 or 25.
So, is there indeed a secret 235kt limitation on fully deployed LEDs?
During a VNAV flaps 25 take-off, does it still bug 230kts? If so, it might be protecting the LEDs, but it ain't protecting the trailing edge flaps. (I'm asking because I don't know. I haven't ever tried greater than flaps 5 for VNAV take-off.)
Another question is: why a hard 230kt figure in the first place? Lazy programming? VNAV knows the flaps up manouevring speed for the aircraft weight, so why doesn't it just bug that? After all, that is what gets bugged via the MCP when flying non-VNAV departures.