FSX Payware Aircraft Gone Bad

[Southwest]

Hi guys,

I admit this isn't about a model that i've been working on or created, but seeing as though the developer doesn't fancy responding to my emails, I thought i'd post my query here.

The aircraft is a total gem, good visuals, nice cockpit and overall, the handing is pretty sound, except for landing. When I land the prop, reverse thurst, cut the throttle back to 0 in order to stop reverse thrust, the aircraft jerks forward at 100%, thrust levers are set to 0 and the only resolution is to shut down the engines or decrease fuel control to almost cut off point from the VC (then overruns onto the grass as the fuel levers aren't set the same for a split second!)

I've copied the relevant cfg sections in order that someone may be able to advise me on how to reduce the affect.

[GeneralEngineData]
engine_type 			= 5
Engine.0 			= 5.652, -9.393, 2.910
Engine.1 			= 5.652, 9.393, 2.910
fuel_flow_scalar        	= 1.000
min_throttle_limit		=-0.250000


[propeller]
thrust_scalar 			= 1.0
propeller_type 			= 0
propeller_diameter 		= 8.206
propeller_blades 		= 4
propeller_moi 			= 38.000
beta_max 			= 45.000
beta_min 			= 15.500
min_gov_rpm 			= 25574.000
prop_tc 			= 0.004
gear_reduction_ratio 		= 17.600
fixed_pitch_beta 		= 0.000
low_speed_theory_limit 		= 80.000
prop_sync_available 		= 1
prop_deice_available 		= 1
prop_feathering_available 	= 1
prop_auto_feathering_available 	= 1
min_rpm_for_feather 		= 700.000
beta_feather 			= 79.3
power_absorbed_cf 		= 0.900
defeathering_accumulators_available = 0 
prop_reverse_available 		= 1
minimum_on_ground_beta 		= 0.000
minimum_reverse_beta 		= -14.000


[TurbineEngineData]
fuel_flow_gain  = 0.011
inlet_area = 1.000
rated_N2_rpm = 29950.000
static_thrust = 120.000
afterburner_available = 0

[turboprop_engine]
power_scalar = 1.200
maximum_torque = 4890.000
max_rpm_mechanical_efficiency_scalar = 1.000
idle_rpm_mechanical_efficiency_scalar = 1.000
max_rpm_friction_scalar = 1.000
idle_rpm_friction_scalar = 1.000

Any help really is appreciated,

Thanks.

 

[lionheart]

Hey Southwest,

There is a bug with turboprops in FSX where the spool up is moderate in startups. Also, there is a bug with joysticks that have a notch point in the throttle for 'reverse thrust.' This can be activated and will then be active always. The 'bug' that works with the throttle control during 'startup' will go into something like 30% throttle because it bypasses the 'reverse throttle notch point' (only during startups) and will over-spool for perhaps 2 or 3 seconds, causing major caos in the sim for a bit.

One way to work around this is to adjust the following setting in the aircraft config;
beta_min= 15.0 // <-- original setting per Microsoft for Cessna Caravan
beta_min= 5.0 // <-- new adjustment (between 0.5 and 5.0 work for most computers).

This will enable float plane turboprops to startup on the water. It will cause 'slight' RPM oddities but will enable the plane to be flyable in the sim.


Oddly, the same joysticks that do this, does not do this on all computers. Activating the 'notch' for reverse thrust mainly causes this. I have the X-52 throttle and do not experience this on ground turboprops, but on the water, its hectic.


I believe this is why Aces took the Cessna Caravan float plane out of FSX was that the water friction was lessened and the turboprop was just getting away, uncontrolable on the water (too powerful, such as at startups).



I hope this helps.



Bill
LHC

 

[Roy Holmes]

Turboprops like the KingAir, have Condition levers. For start and taxi, they are supposed to be in the ground idle position. In FSX the condition levers are "mixture" controls and, if you set them at about 5% the result is that torque and prop RPM are reduced. This allows the plane to be taxied normally.

The trick is setting the mixture low enough to have a effect, but not get it in the shut down position. I would imagine that a throttle mounted mixture control could affect both engines equally, though I have never tried that.

For flight, you move the condition levers fully forward to flight idle.

Anyhow, the key is to get the mixture/condition levers to ground idle anytime you want sensible taxi style power. With that and Bill's changes you should be in business, and if not there is something bad in your plane.

As an aside, the FSXA twin turbine helicopters have the same type of engines as the KingAir, but you can not control ground idle as I described, because they have a Govenor in the config file that is designed to control torque to keep rotor RPM at 100%. The mixture control just works as a fuel on/off cock

Roy

 

[jx_]

are you saying the engine spools to 100% coming out of reverse to forward?

If so, what happens if you slowly reduce throttle from reverse to forward? (I imagine it is the negative throttle portion and not a reverser switch.)


The problem could be in: min_throttle_limit =-0.250000

Having it set to 25% gives you a very narrow window where the FS reverser system will transition. The transition itself is set to a width of min_throttle_limit, and the smaller that number is the more coarse the reverser function becomes. When it is too low, you will get forward thrust as the engine is still commanded above idle when the reversers close. Try setting min_throttle_limit to -1.00 and see what kind of difference that gives. If that fixes the issue, you can reduce that number as needed until you find the correct value.


This applies to turboprops and jets.

 

[Southwest]

Sorry for the late response and thanks for all the replies.

I changed the value to -0.5 and the transition is perfect, just as it should be, thanks!

 

[jx_]

You're welcome

 

[Roy Holmes]

Joe,
Good advice, good problem fix, keep them coming
Roy