What is the gradient of the standard net flight path analysis assuming no obstacles?
There is no NFP analysis if there be no obstacles. Either you are MTOW or WAT limited (ignoring cruise and landing considerations which may further limit TOW).
Also I wrote "will diverge by 0.8% for all the takeoff profile by the obstacles" obviously meant minimmum, by the net.
That's fine, I don't think we have any disagreement there.
I thought takeoff segments were only for N-1 engines. Thats why I wrote that for 2 eng a/c, it is 1.6%.
Provided the aircraft is operated such that the GFP remains above the NFP, all is fine. Again, we don't have a disagreement on this point. However, again, you appear to be overlooking the distinction that 1.6% is a minimum WAT requirement and, apart from being that minimum available gradient, has naught to do with obstacle NFP analyses.
I am not a perf engineer neither a perf instructor,
Which is why I like to see robust tech discussions in this Forum. The new chums coming up through the ranks get to see more than perhaps what they were exposed to during their initial training and they get the benefit of line observation feedback from you guys who are out there trying your best not to get killed. Unfortunately, unless the performance instructor has a sound ops eng background, the instruction often becomes a bit tenuous. There are non-engineering pilots about who do have a very good background but they are in the minority. One who comes to mind and posts on PPRuNe is Centaurus.
what these have to do with single engine performance? SIDs and ATC requirements are for all engines ops.
Nothing, unless you find yourself with a quiet engine during the procedure. I introduced these simply to list a variety of climb considerations which the Commander should be taking into consideration in his/her overall decision making processes.
The relevance of the confusion about minimum gradients is that the Climb (WAT) limited gradient is an air gradient and obstacle clearance gradients are related to the ground, ie influenced by wind.
And, if I may emphasise, WAT is for nil wind, OGE.
There is a huge amount of confusion caused by fuzzy thinking at ATPL level
Oh, indeed, good sir, which is why this forum is so important on the site for the educational imperative. Competent instructors, such as yourself, are, unfortunately, fighting a rearguard action against the rest. I despair at the training organisations who use their flying instructors to teach theory when many of those instructors barely comprehend the subject details themselves.
mostly due to the fact that no one is talking about performance these days.
Which is why this forum is so important. We have a good cadre of very expert tech people on PPRuNe - if you were to consult privately, you would pay through the nose for what you get free in this Forum.
You get a number, we are good to go.
Most of the time ...
But a/c these days are so overpowered that make ppl stop thinking about it
That just means the weights are pushed up. Where a major problem arises is, especially for twins, we see tremendous performances routinely AEO ... however, OEI and seriously weight-limited and it's a very different story.