Sorry, Tom; you're down 2 grand.
First, it's interesting that you keep saying everyone's doing it (in your opinion) wrong because FSI & co have been teaching it for years. The reality is that it's only recently that they've started to teach it after years of pressure to correct their previous errors. They used to teach all sorts of strange things that were not as per manufacturer, and have the court cases to prove it!
Second, a lesson in aerodynamics; V2 is most certainly not the best angle of climb speed. It is the minimum speed for climbing out following an engine failure at V1. On swept wing jets, Vxse is between V2+10 and 20, which is why many manufacturers' advice for an engine failure above V2 is to slow to V2 + 10 or + 20 depending on the type. It is also why when you get into airliner size machines they give you the figures for the option of trading runway length for improved climb by increasing the speeds.
I agree entirely with you that flap retraction is a function of speed, not height. I also agree, I have never seen an AFM or manufacturer's checklist that gives a height, although many say "not below 400ft". The significance of the 1000 or 1500 (or even 400 for those so inclined) is that it is the trigger to start accelerating for flap retraction. The reality is, though, that most bizjets have so much performance that you are normally already past the minimum speed and so can retract the flaps immediately. I have seen crews cockup in the sim when heavy, hot & high due to this not being the case, but just because crews don't understand the SOP (usually due to poor training) doesn't make the SOP wrong.
So why is the SOP as it is? There are two reasons, both of which have already been posted.
The first is NADP's. All EU-OPS operators are required do do them. So before we go any further, anyone retracting flaps at 400' on a European commercial operation is operating illegally. In this context, you are actually better off having some flap down, because the drag and the pitch attitude change of flap helps with the issue of body angle. 15 to 20 degrees is no problem, but more does start to be uncomfortable in the back particularly for pax in rear facing seats.
The second is the engine failure in the climb case. All twin engined jets will do a far better gradient on two engines even at a much higher speed than they will OEI. For example, at 200 knots 2000fpm is a 10% gradient. That is off the scale for most aircraft OEI. So in the event of an engine failure in the climb you are already above the NTOFP. During the period of reducing speed to V2+10 you will be climbing better than at the steady V2 had you had an engine failure, and when steady at V2+10 you will still be climbing better, see above. So you have guaranteed your obstacle clearance.
However, if at some point before the engine failed you have retracted the flaps, while you start off in the same position you rapidly move into no man's land. You mention the Challenger; there is no second segment speed clean because flaps up is not an approved takeoff configuration. So what speed should you fly? And what is the performance at that speed? If you fly at Vfto/Venr or whatever the manufacturer calls it, you may or may not have to accelerate to reach that, and the gradient may or may not be better than V2 with flaps.
Most of the time it is, but not always. And the passengers are not paying for "most of the time" or "probably" - they are paying for definite answers.
So to summarise, leaving flap retraction to 1500ft or similar has advantages in being the approved noise abatement procedure and guaranteeing obstacle clearance in case of an engine failure, with the bonus of the commonality of procedures between normal and OEI ops also mentioned. So why do it any other way?
Interestingly, if you read D.P. Davies, the airlines were having this discussion 30 years ago. It's nice to know we're at the cutting edge of the industry!
So, Tom, you can send the cheque to me made out to the Campaign Against Sobriety and Hunger (C.A.S.H. will do!)
