am I nuts to suggest that we can do what the men that build the plane say and raise the flaps at V2+x
Yes - because
they don't say that!! I've posted the manual quote directly for you several times and it says
not less than.
Re accelerating at 400 or 1500 feet - a history lesson:
1500 feet is an arbitrary number that marks the change from the takeoff phase to the enroute phase in terms of required obstacle clearance. It's the lowest height where you're likely to meet the enroute requirement of 1000' above obstacles.
Early jets couldn't climb at all with flap down OEI at max continuous; and because of their poor climb and acceleration even at takeoff thrust with water injection, they could only make it to 400' before having to level off and start accelerating to be clean before their 5 minutes ran out. I understand that the 400' figure was a battle between manufacturers and regulators; manufacturers wanted lower and were told "no".
Later, we get jets like your 601 that can get straight to 1500 (just); this allows them to take more weight in a scenario with distant obstacles below 1500 by delaying acceleration until you are above them.
More modern still a/c (604/5) can get higher still - and we have graphs in the manual for extended second segment climb. So
we quite often are climbing above 1500' before accelerating if it is required for obstacle clearance. Zurich RW28, for example, AA is 3410', which is 2020' above the runway.
So the answer to your question is that we use 1500 normally because at 95% of airports we are clear of obstacles and are only interested in rate of climb, not angle.
Your logic for your profile appears to work for the 601, but only because it is a special case on two counts;
1) that the flap retraction minimum speed and the final segment climb speed are the same - on most aircraft there is still acceleration required. Of course, if you adopt my logic this problem goes away, because you leave the flaps down until you have reached Vfs
2) because the final segment gradient is always better than the 2nd segment. There are plenty of aircraft where this is not the case, because the reduction in thrust from TO to MCT reduces the performance by more than the gain of getting the flaps up.
And on aircraft like the Hawker with flaps up performance data,
if you've looked up the appropriate clean V2 then you could use that in case of an engine failure after flap retraction but below AA; But that comes back to introducing too many variables to expect the average pilot to cope with.
BizJet, the point I meant to make (but didn't type) was that if I was struggling to clear an obstacle I wouldn't give a fcuk about noise.
Yes, and quite right too. However, the original question was why do we fly the profile we do on all engines. And the answer is because
as well as planning for an engine failure at any stage, we have to comply with the normal operating rules (noise abatement, etc) and make the whole thing reasonable to expect people to fly - which should in the process cover any liability issues!
This may mean we can develop a more appropriate noise technique for business jets that we can actually fly!
I agree that the current framework is written entirely around airliners, and is in many ways not appropriate for bizjets; however, until it is changed (oh, look , there's a pig flying past my window...) we have to work with the rules we have.
Enjoy the rest of the weekend.
