hello againn apruneuk
the issue is that it links to putting together cohesive arguments about NAP to the authorities. At the moment most people don't really understand performance and the way its taught confuses people.
For instance. The reason the Hawker manual says 2nd segment goes to 1500 feet or to 3.5 mins is thats the point at which you need to accelerate and take the flaps up. Its actually the flap going up that changes the segment - you go to third segment (level acceleration) if you need it to accelerate and because your engines are limited to 5 mins max thrust you level at 3.5 mins to accelerate enough to take the flap up and do a final segment climb to 1500 feet where you would level accelerate again and climb at Venr or Vfto whatever you choose to call it.
So if you raise the flap at V2+10 at any height you have entered final segment climb, if you keep accelerating to Vfto you are in the enroute climb. There are advantages to climbing at Vfto - there's no level segment needed at 1500 for the final segment climb because you're already at the required speed and its easier to fly with a failure. But this is also true if you are at V2+10 clean.
The argument regarding needing a further margin over V2+10 is also not valid - you actually need less lift in the climb than in the level segment and everyone seems happy to raise the flap at V2+10 in the level segment. The margins are already built in as explained in a previous post.
I don't understand the logic of flying a less efficient departure, climbing against unnecessary drag. It simply not true that its mandated - thats urban myth. I don't really care how people choose to fly the planes but we shouldnt make up rules that simply don't exist. This myth of a 400 foot flap retraction height and even the 1500 foot one just causes confusion in pilots and they don't really understand the problem. I've been accused of making up my own rules and all sorts on this forum simply for saying "why don't we do what the manual says" and its revealed all sorts of holes in peoples knowledge which is also why I object to how its taught. In many companies, a call of 400 feet is the trigger for flap retraction and its totally without logic.
anyway, as you say, got my knickers in a twist..
but they are very valid points eh..