Prop Question

[_486_Col_Wolf]

Another question that's probably been answered before but... does anyone know how to get the prop on certain planes to stop spinning after engine shut down? Some of mine do stop while others stop then start spinning in the opposite direction after shut down.

 

[bearcat241]

Ok, this one is a bit complicated, but here it is:

Generally when a prop is designed in the modeling to spin in one direction and a user or re-modeler edits the aircraft.cfg propeller section for counter rotation, the prop will spin in the counterclockwise direction through shutdown until it reaches a random RPM moment at which in begins to spin in its originally designed clockwise direction. This is rare, but as you've witnessed it does happen. Check the aircraft.cfg for CCW rotation and revert it back to CW.

The other problem with "continued rotation" long after shutdown suggests erroneous data somewhere in the prop sections of the *.air file, i.e. 510, 511 and 512. Using AirEd, the quickest remedy is to find another model with similar prop dimensions and blade count and copy its sections 510, 511 , and 512 to paste/overwrite into the same sections of the offending model.

 

[Allen]

I think the fix for the prop that keeps spinning around is 509 *Engine[Per Cyl]/TurboProp Friction Torque vs RPM. Most aircraft have things set up around so at -500 RPM they have -21.0 friction and at 0 RPM they have 0.0 friction.

Try having the -500 RPM have more negative friction. This this sound odd but I think that is how it is fixed.

 

[bearcat241]

Allen, records 508 and 509 can only be edited in hex, as they are graphical mini charts in their display. Most people aren't going to venture into that briar patch without extensive experience in hexing air files. That's why i intentionally omitted these two from the conversation as they don't really need to be addressed if the other mentioned records are dealt with appropriately. The biggest culprit in the continuous spinning prop syndrome is the prop MOI in 510. Lower is better, somewhere around 30 to 35 should do. This is actually the only specific entry that allows one to text edit rotation friction in the air file in one step.

If you step outside the standard CFS2 setup where all of the engine and prop data are in the air file and go with the FS2004/CFS2 config, you can text edit the aircraft.cfg likewise to match the air file data. This is taken from the cfg of my customized "stock" Corsair:


[propeller]
thrust_scalar = 1.432
propeller_type = 0
propeller_diameter = 13.33
propeller_blades = 3
propeller_moi = 53
beta_max = 65
beta_min = 15
min_gov_rpm = 405
prop_tc = 0.01
gear_reduction_ratio = 2
fixed_pitch_beta = 30
low_speed_theory_limit = 80
prop_sync_available = 0
prop_deice_available = 1
prop_feathering_available = 0
prop_auto_feathering_available = 0
min_rpm_for_feather = 700
beta_feather = 88.5
power_absorbed_cf = 0.9
defeathering_accumulators_available = 0
prop_reverse_available= 0
minimum_on_ground_beta= 0.000
minimum_reverse_beta= 0.000
rotation = 1

This data matches that in the air file as well. The entries in bold type are most critical to this topic.

 

[Allen]

Allen, records 508 and 509 can only be edited in hex, as they are graphical mini charts in their display.

Nope. The graph are editable in AirEdit.

The Left and Right Arrows move you Left and Right. The Blue line is the point your currently at. For 509 *Engine[Per Cyl]/TurboProp Friction Torque vs RPM. X is RPM of the engine and Y is Friction at that RPM. Move the blue line left or right to the point on the graph you want to edit than hit X or Y. This will open a small box on the graph where you can change the data. Type in the number you want than hit Enter to save you change and the graph will update and show your change.


View attachment 49387
View attachment 49388
View attachment 49389

 

[_486_Col_Wolf]

Tried replacing 509-512 in the AIR file one at a time. 509 seems to be the only file that will stop the spin. If I replace it with a working file from another A/C it stops but performance is greatly reduced. I will try to edit the existing 509 file over the weekend when I get some time. Thanks guys for putting me on the right track.

 

[bearcat241]

Well alright Allen...all this time i never knew that it was that simple to edit these mini charts. Learned something new today. Thanks

 

[Sarg Willy]

Thank you Allen an old dog just learned a new trick