P3D v4 AI takeoff unstable pitch

#1
Recently noticed that some ai aircraft particularly all FAIB models fluctuate in pitch and climb rate just after liftoff which is odd looking, as though trying to compensate for excessive climb rate. I do not remember or rarely seeing this before. AIA and TFS models appear to have a better FDE in this regard with a stable maintained pitch and climb rate after takeoff. I have tried to compare major fde parameters between the two to figure out any problem variables but so far haven't been able to find out anything useful with most variables having similar values. Has any one else looked into this and found more info on the causing parameters?
 

=rk=

Resource contributor
#2
Absolutely. I am pretty sure if one could tune in AI behavior by comparing major parameters, all AI planes planes would work magnificently. They would start, stop, jump to 10,000 foot elevation and perform any of the 5 or so major parameters exactly as they were programmed to. The reality is, with scores of parameters and a simulated characteristic that not unexpectedly mirrors the reality, flight tuning is difficult, who would have guessed. The info you seek accumulates after long hours of incrementally changing values and testing for observable results. I am sure you are welcome to improve on the flight characteristics of the FAIB AI models you use personally. Erez Weber might even invite you to share your data.
 

tgibson

Resource contributor
#3
Hi,

For me this is usually due to the plane trying to rotate prematurely for the given wing_area. Either increase the wing_area (to rotate at the current speed) or increase the flaps_up_stall_speed (to increase the speed at rotation). Note that increasing the wing_area value affects many other parts of the flight dynamics.
 
#4
Thanks for the suggestion. On changing the above mentioned parameters however could not reduce the ai pitch movement. In faib a320 tried with values 162 in place of 142 and also 122 which didn't cause change in takeoff behavior. The rotation happens at around 160kts and lift at 170kts. AIA 738 which does not show the pitch movement has stall speed = 122 in the cfg.
 
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