ATPL perfo
hello all,
checking all the different opinions & theories, all correct, there seems to be no consensus on what is the correct answer to this question.
so let's analyse two different scenarios : 1) aircraft is stabilized at cruise IAS/MACH, with a certain cruise N1, Fuel flow, Thrustlever position, resulting in correct thrust output in accordance with actual outside conditions of Temperature & Pressure. now the aircraft enters a warmer airmass. what is happening ? due to the increased Temperature & corresponding reduced density a thrust deficiency develops & the aircraft keeping altitude constant will have a tendency to slow down. now the automatics(or pilot intervention) are kicking in to keep above parameters constant. so up(forward) go the thrustlevers, N1 increases, Fuel Flow increases, thrust output goes back to original setting. we have now a situation where SFC = (FF/F) is higher & TAS is also higher, due to reduced density. this would correspond to answer B) & most probably would happen in the real world. BUT that is NOT the question asked here. so let's go for scenario 2). aircraft again enters a warmer airmass. Autothrottle is off. initially, due to reduced density, N1 & TAS increases only slightly trying to temper but not sufficiently the Thrustloss, which is exacerbated by reducing N1 back to original setting(pilot intervention or because N1 was already at a limit) . now FF will be slightly lower but F will be much lower, resulting in SFC increase. due to the thrust deficiency the aircraft IAS/M, will slow down. TAS will reduce at a slower pace than IAS, due to reduced density, but it(TAS) will reduce. this scenario correspond to answer D) TAS decreases & SFC increases.hope this reasoning makes sense but i am open for any correction
greetings to all,
bm