De-rated power settings question

[john_tullamarine]

ISA reference temperature is 15º celsius measured at Alicante

a chap learns something new every day ...


It (ISA) dates back to an early definition of worldwide average SL air temperature (15C or 59F)

I suspect (from aging memories of reading on the history of the matter) that the stats upon which the ISA is postulated are based on North American profiles dating back quite a few years, now.

It is important to accept that it doesn't make any difference what standard atmosphere you use (and there are a number in common use) so long as everyone talking the same subject are using the same standard atmosphere. In general it makes good sense to base discussions on a standard atmosphere which bears some resemblance to the typical atmosphere of interest but, at the end of the day, it is just a convenient means to the end of reducing performance from a given set of ambient conditions to some (arbitrary) standard conditions for the purpose of discussion and comparison ...