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Calculating proper assumed temps/derates

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I've had the TOPER addon for a while now (it's a takeoff performance calculator), but I noticed that for the 300 it only has data for the 22k engines, whereas I believe the IXEG has 20K. So lets say TOPER says use an assumed temp of 67C, I imagine a 20K engine shouldn't derate quite as much as that since the engines aren't as powerful. I usually shave a few degrees off whatever temp TOPER gives me, but is there a more precise way of calculating it?

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I too bought TOPER and it is a waste of money, even for the aircraft with indicated engines (different from iXeg), too imprecise calcs.

To manually determine assumed temperature and corresponding N1 is a matter of looking up 3 tables in FCOM, done in under 2 minutes. Another 2 to determine V speeds. Can take more time if runway is contaminated (assumed temp method not allowed). All given you have determined TO maximum performance-limited weight (which you must always do).

Edited by NZWW

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