deefer, that bit is interesting for my aircraft.
Comparisons of a departure at MAUW from sea level at 20 degrees give 5.8% for the final segment and 5.7% for 2nd segment.
40 degrees, 41,000lbs, sea level, second segment is 5.0 % and exactly the same for final segment.
I'll do more tomorrow (I'm visiting inlaws..)
Although you can't account for the credit, the conditions for 2nd segment are with the APR (power reserve) triggered which is an extra 2% N1. The engines are producing significantly more thrust in this condition and you are limited to 5 mins. For the final segment tables the engine conditions are max continuous so significantly less thrust. Achieving the same percentage climbs with less power would indicate a more efficient climb but that is a hard one to argue so I can only claim the same gradients. I promise to post it if I find conditions where final is worse than 2nd segment.
Dont forget that the APR would be triggered in the event of a failure anyway so you would absolutely definitely out perform the quoted final segment numbers (engines delivering more power), there would only be a requirement to reduce power to max cont after 5 mins with no level (third) segment so dist obstacle clearance performance with the flaps retracted would ALWAYS out perform flapped to 1500 feet. You would still need to fly a level segment to accelerate to enroute but it would be shorter than from the flapped condition (you're already going faster and there's no segment where you are raising the flap).
Still failing to see the downside..
I re-read the Bombardier AFM for a normal take off today for the 601. It states flaps up at 1.25Vs which is typically V2+4 when light to V2+7 when heavy. Flaps up at V2+20 (quoted in the Bombardier training notes and on the checklist) already has a margin built in.
every days a school day ...