I’m trying to address two problems with the ground handling of the otherwise lovely Iris PC-21.
If you want to apply these changes, remember: Always make a backup copy before you change any aircraft file!!
Problem 1: Directional control on the ground is poor
In the Iris PC-21 aircraft folder, navigate to flight_model.cfg. Create a backup copy of this file, and then make the following changes:
In the section [CONTACT_POINTS] change the following lines:
max_speed_full_steering = 15 ; instead of 10
max_speed_decreasing_steering = 60 ; instead of 20
min_available_steering_angle_pct =0.1 ; instead of 0.2
In the section [FLIGHT_TUNING] add the following lines:
ground_high_speed_steeringwheel_static_friction_scalar=2 ; default is 1
ground_high_speed_otherwheel_static_friction_scalar=2 ; default is 1
Save the file. You will need to restart the msfs sim (not just the aircraft) to pick up these changes.
What does this do?
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With increasing ground speed, rudder input will be translated into smaller steering angles. The above changes makes it so that the aircraft can still make tight turns below about 8 kts, but becomes progressively stable until about 30 kts, above which it is twice as directionally stable as with the original setting.
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When spinning, for example on takeoff run, the wheels have progressively less tendency to slip sideways. The above change reduces side slip tendency by a factor of 2 compared to the original.
Problem 2: Taxi speed on idle power is too high
In the Iris PC-21 aircraft folder, navigate to engines.cfg. Create a backup copy of this file, and then make the following changes:
In the section [TURBINEENGINEDATA] change the following lines:
low_idle_n1=12 ; instead of 15
min_n2_for_fuel_flow=10 ; instead of 13
What does this do?
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Given the way in which the PC-21 engine settings are written, the N2 low idle setting (which appears on the gauge and in the manual as 54) will be translated by the msfs engine into the corresponding N1 low idle setting (which determines the thrust at low idle power). With the above change, you will have to add a tiny amount of power to get the aircraft moving, but then it won’t go as fast at idle power as the original.
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Min N2 for fuel flow will always have to be 2 points lower than min idle N1, otherwise fuel will remain shut off and you won’t be able to start the engine.