timing V1 was discussed for quite awhile, but was generally dismissed in civil operations in the USA. I do understand that some military operations did at one time , time v1.
our airline has us start the V1 call 5 knots prior to V1 in order to insure that the words are complete at V1 and not started at V1 (of course for 30 years before that, we started the call at V1)
About engine performance and the like. After the Air Florida crash in DCA (washington, dc, potomac river) I would like to think we all learned to take a good look at N1 as well As EPR...not just EPR. In this type, I can't see any takeoff power setting below about 97percent n1 give or take.
IF there was a stall (aerodynamic) on takeoff, I can understand the wings rocking or dipping as the plane was about to leave ground effect (teal effect for real old guys)
(as an aside, I have told my favorite people f/a's and pax alike that they should time the takeoff and that most jets rotate about 30 seconds after application of takeoff power...longer for high, hot,heavy, shorter for cold and light...if you are sitting in back, what do you have to measure the takeoff?)
I have these questions for investigators:
what was the position of the flap/slat handle?
what was the position of the flaps/slats (though * see below)
what was the position of the throttles
what was the position of the pilot seats.
*It might be a ''no brainer'' that if the flaps/slats were extended, there was no configuration problem, but part of stall recovery at this part of flight is to make sure the slats/flaps are extended