Nope, #22 did not show a lack of knowledge. Came here 2 years later, guns blazing with the opposite of what the correct knowledge is, shaming around.
Both your points are solved with operators who are thorough. It's reading the regulations and AFM alone, without the needed expertise, which could lead a young gun astray. Always has been and no need to ask how we know.
Reading the thread again, #11 has the key issue unanswered. He did not get different speeds after selecting another flap for the modified temperature. The calculation threw him a different OPT flap as a result after adjusting the OAT while still well below the flex and, god knows, even the corner point. That should not be happening, right?
Well, it did. Not as a function of the AST Method but a good outcome of the Perf SW efforts for an optimum result. Following the proper AST methodology,
at first, thou shall calculate (max) PerfLIM TOM for the given OAT (and some other bits which might be OEM specific). This search for PLimTOM(@oat) will also involve some serious magic with V1/V2 ratio (a.k.a improved climb) and clandestine adjustments to ASDA. Even for a minuscule difference of 1 kg rounded up, the result for OAT=9 might give you 1+F but OAT=10 shows flap 2.
And then, the WHOLE performance calc is run again (and again) with ever-increasing fake OAT (even above max allowed environmental envelope) until the value of PLimTOW(max assumed temp) drops down to the actual TOW which is when Tflex is found.
Most likely by a present or missing SW feature, the flap setting providing the best PLimTOM(oat) at the first step is locked, and the iteration for max assumed temperature is only done with a single tkof configuration.
The associated N1 for TOGA @ (max flex temp+ELEV+QNH+bleed+anti-ice) is known from the Engine manufacturer. The pilot will feed the chosen Tflex
somehow into the engine data pipeline and the engine will later respond with the same N1 which would be the TOGA N1 if it actually was Tflex outside. The sweet part already mentioned is that the thrust provided by N1(flex@oat) is markedly greater than that calculated for N1(toga@t-flex) as the density of air received is higher and the mass of air accelerated air heavier (F=-a*m) eventhough N1(flex@oat) is purposely selected identical to N1(toga@t-flex).
Those impressed by the inherent margin uncovered above should also consider the correlated effect of increased density on airfoil performance. If not completely flabbergasted then, there is a truckful of GS(v1) & distance-to-IAS(v1) happiness to be discussed under the calculated assumed temp v.s. real OAT, nicely perched on top of the whole majestic Ekin(v1) pedestal.
Not satisfied yet? Go fly something else than the venerable B737 and get an extra 1 second of recognition time and an adjusted bite of deceleration.
