A320 flex to temp


The flex to temp setting on the a320, how do I work out what number to enter?



I think this is a good point to start with:


Still confusing, lol.

I thought I base it off the current outside temp.

temp, qnh, runway length, TOW, so much variables

1 Like

Yeah, I might just try a random number and see how it goes, just interested to try taking off in the flex detent.

I guess it these days as I’ve flown a lot over the years. Higher number you put in the less power on take off. Probably when Fenix A320 comes out you can get those values.

1 Like

So for an example Heathrow or any long runway for that matter what would you put in?

So it’s a longer runway I’d add 20 degrees. Shorter runway like 10. You fly enough you can figure out rough guesses of what your v speeds should be for your weight and runway length.

1 Like

I created a runway performance spreadsheet to enable me to calculate all the various take off and landing options. It is based on performance data published by Airbus for the A320 and will provide a flex temp calculation based on the airfield runway selected and METAR data. I still need to further develop the Flex temp calculation, but it seems to work. It’s free to use from Flightsim.to.


Thanks, how do I open them files, Im on mac, have the zip file but opening it keeps opening more zipped files.

Is that on top of the current outside temp, so say its 20 degrees outside, enter 40 for longer runway?

1 Like

I don’t pretend to be an expert on mac operating systems. I believe you double click a zipped file to open it. The spreadsheet needs a copy of Libre office, which is free, to work. I believe this can be used on a mac, but I don’t have one to try with. The Flex temp you wish to use is entered in the Performance page of the MCDU. Obviously the Flex temp must be higher than the outside air temp, but in addition there are minimum and maximum flex temp figures, which vary between engine types and atmospheric conditions. If you just want to try it and see the effect, pick a longish runway, say Heathrow EGLL and even with a full passenger load a flex temp of 60 should work in today’s air temp.

1 Like

Ok I see, will check that out. Thanks again.

I usually rough estimate at either 45 or 65 degrees, pending on runway length.


Indeed, it is not easy.

Something like 50 is a normal value for most airfields under MSFS conditions.

For the calculation, this tool may be helpful:

edit: but no matter what I enter there will always be flex 43? :wink:


This application uses your simbrief plan to calculate flex and velocity A32NX Performance Tool [FLEX Calculator - Automatic][Simbrief] » Microsoft Flight Simulator

1 Like

For flights of under 60ton takeoff weight you can use +66 quite comfortably at ISA conditions on runways of at least 6000ft.

1 Like

Not sure what I’m doing wrong, I just tried a flex temp of 60 at Heathrow, I put throttle to the flex detent and not far off the ground I start getting the overspeed warning.
Perhaps I’m not entering a setting in the performance page somewhere that I should be.

Bear in mind I’m on default a320 here and normally I use TOGA but just wanted to try different things.

Any ideas guys?

This utube video explains how you program the MCDU. The guy knows his stuff so it’s worth watching, but if you just want to know how to program the performance, flex temp page of the MCDU it’s 22 minutes into the video.
I think most people have migrated away from the default A320 to the Fly by Wire A320 as it’s very good.
Good luck.


Generally the concept yes