Colleagues.
I'm very interested in this scenario. I've asked the question a few times, but had less response than this thread. Please may I contribute. As an aside, I've asked for any links to Boeing SOP's on how they conduct B378 departures. No success as yet.
Yes I've heard about the 1000'agl and the N1% engagement criterea on departure. Why, if there is no limitation problem do some operators use Flaps up? It wasn't even a limitation on the B732, though Britannia did it; and therefore so did many others. However, when BY received the B767 they engaged at 400' and watched what it did and then devised their training syllabus.
Moving on, why do some N1% operators still use Flaps up after a G/A? That is a more stressful manoeuvre, less practised, less height to level off etc. etc. and yet it is done in a high work load manner. Many mistakes seen in sim on the supposed simple manoeuvre. Very odd.
I've tried it in the sim on a V1 cut. A/P in at 400' and just fly the rudders. As PF it gives lots of capacity to follow PNF's analysis and watch the shop. It was a doddle. Same in an emergency turn and same in a 2 engine or SE G/A.
So why do most EU operators I've heard from on Prune not allow it?