A320 Flex Calculation

[TwentyRetard]

Hello ,

I wonder about FLEX (ASSMD) temperature how calculated on Airbus A320.But counter to based on software calculation i want to calculate it via formula based on paper calculation.

Regards.

[barit1]

The essential method is to use the airport analysis (r/w, obstacles, pressure altitude etc.) and the TOGW, and determine the maximum OAT for a legal TO in this condition.

This is the max FLEX temp.

You then set thrust equal to the rated engine thrust for that FLEX temp. (For V2500, set EPR for that FLEX OAT; for CFM56 use the sliding-scale N1 chart entered for both actual and FLEX temp)

[TwentyRetard]

thank you barit1, but im more looking for an absolute chart or formulization to pick the best value according to the conditions as u've been described (r/w,TOGW etc.)

Regards.

[potkettleblack]

I think what you are after are the paper based Octupus charts. From my basic understanding on what goes on "behind the scenes" these are prepared by a operators performance engineers using the Airbus Octupus software. They are airline, runway-intersection, config specific. With a take off weight, wind, QNH and temperature, you enter the paper charts and select a suitable flex. This is adjusted for things like low pressure and the use of engine/wing anti icing. The flex you select has to also fit within a whole host of values such as tref, tvmc. OAT etc. The V speeds for that particular flex and associated weight must be above the minimums and v2 must be equal to or greater than vmu for the given take off weight.

Thats a very summarised overview. Try googling Octupus and see if you can grab any off the internet.