In the SDK documentation, the parameters rudder_lift_coef and
elevator_lift_coef in the [AERODYNAMICS] section of flight_model.cfg are
documented twice, differently: elevator_lift_coef Define the slope of the lift
curve of the elevator surface of the aircraft. Default is 5.0. This can be
scaled with the elevator_effectivenessparameter in the
[[FLIGHT_TUNING]](https://docs.flightsimulator.com/html/Content_Configuration/SimObjects/Aircraft_SimO/Flight_Model_Definition.htm#h1)
section. vs elevator_lift_coef This defines elevator lift vs elevator
AoA.
This should be aspect ratio dependent and fall between 3 and 5 for most planes
(5 is very twitchy and stable). The theoretical maximum is 2Pi. And ditto for
rudder_lift_coef. Which one is correct? In the first one, what does the slope
of a curve even mean when you don’t tell what the units of the axes are? And
if the default is 5, that is then said to be “very twitchy and stable”. How
can something be twitchy and stable at the same time? Also related, as these
are single numbers, why does the [FLIGHT_TUNING] section then need to have the
elevator_effectiveness and rudder_effectiveness parameters that just scale
them? If one wants to scale elevator_lift_coef, one could simply specify a
different value for it?
Looks like someone was a little overly zealous in adding this new .cfg
parameter to the SDK. Both descriptions are correct; imo they should be
combined. There appears to be a typo in the parenthetical in the 2nd
description. I think it should say, “5 is very twitchy and 3 is very stable.”
As for your comment regarding the coordination with the effectiveness
parameters in the [Flight Tuning] section, I wonder the same thing except from
the opposite direction. If we already had the capability to scale the default
lift curve slope for the rudder and elevator controls, why do we need new
variables to accomplish the same function?
SU6 saw an update to all the documentation relating to the flight model and
engines, and as such the issue of the duplicate parameters was resolved with
that update, an the explanation greatly expanded too.
https://docs.flightsimulator.com/html/Content_Configuration/SimObjects/Aircraft_SimO/flight_model/aerodynamics.htm#elevator_lift_coef
Sorry for any inconvenience this may have caused you.
As i was about to post I saw this post in the search. I believe the
description is still not right. it says in both the number is between 1 and
pi, not 2 pi and then the default is 5
Thanks for this post - before it I hadn’t given those parameters much thought
and this discussion has certainly added to the cumulative knowledge needed to
fine-tune our flight models.