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A320/A321 IAE flex takeoff performance fall from sky

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having a thrust performance problem with A320/A321 pro IAE engines only. the cfm work well. this has happened with 5 flights in row IAE only. takeoff performance at different airports over the last week KSAN, KPHX, KLAX, KLAS and now KSFO today at 1pm KSFO to KSAN. it had a F79 suggested takeoff performance calculation based off perfromance calculator. 


at the time KSFO:

winds were 320/11

OAT was 60F

TOW was 135194


ATC assign me 01R takeoff


Perf calcs gave me :

Flaps 2 config

F79 for temp

V1: 149

VR: 150

V2: 156


The plane was off the end of runway almost in water and barely lifted off. i had to pull back at 137kts or else i end up in the drink. the plane was barely climbing and when i hit 800' than speed declined and stall warning occurs. had to manual toga and get up. 


this has happened 5 times in row A320iae or A321iae models only. has even happened at KPHX where runway is 10,000' long. happened at KLAX KLAS too. 


Is there a fix for this? why does this happen in IAE only ? need help please . 

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2 hours ago, airtahitinuiforever said:

Flaps 2 config

F79 for temp


Looks like a miscalculation issue:


From FCOM IAE Engines limitations:


TFLEX cannot be:

‐ Higher than TMAXFLEX, equal to ISA + 55 °C. <-----  no more ( 15 + 55 = 70°C ) 

‐ Lower than the flat temperature (TREF)

‐ Lower than the actual OAT.


and in this RWY and this Weight , for F2 takeoff  speeds will be around:


v1= 141

Vr= 141

V2= 143


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ok thanks polo will try again and see. i use the apsoft airplane toolbox for xplane. have created a profile based off aerosoft data. when i inputed:





Clicked the Metar button (metar matched atis and matched ActiveSky)

Clicked Calculate


it gave me Config 2 F79 @ 1pm today with the above weather temps and winds. I just went to apsoft airplane toolbox no and inputed same info with the correct engines and it gave me now:





Hit metar 

hit calculated and now it said this:


Config 1+







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So maybe I spoke too soon . Just took off 3 min ago from KSAN. Same problem . What is goin on here with the IAE models ? This time I took off from Ksan and used different perf calculator. Used the Wabpro online .

ksan metar 5-10min ago : 69F winds 355/02 OAT 16c alt 3021. 

Tow 140030 lbs 

runway 27 departure 


so using wabpro perf calc (last night I used Apsoft airplane toolbox)....it gave me these 2 calcs for 1+ & 2


flaps 1+ config 

flex 70C





flaps 2 config (THIS IS WHAT I USED)

flex 70c





i reached the end of runway only at 130kts and crashed . How can this happen 6-7 times now even on a runway that’s 10,000 ft like kphx. I’m not suffering from this on CFM model. This is 2 different calculators. The iae model A320/321 struggles to pickup speed . 

can some1 please help or advise 


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I looked on forum and this has been addressed goin back to 2014. I have not read on any of the forum threads that there is or was a fix. Even when I’m taking off a320A321 IAE ; I look at the speed tape on PFD and it’s barely moving compared to cfm and obvious common sense looking out the window the plane struggling to pickup speed 

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