Possible bug - FCLS Roll axis Limiter in Cat III.

[robgraham]

I'm saying this as a possible because It's late and my maths could be out the 2004 documentaiton states a 40% reduction in the roll axis inputs on what you get with CAT I (for Matt/Nineline/etc FM section on FCLS Limiters, specifically Roll Rate Limiter) testing just now as I posted in another thread I got in Cat I

 

225 Degree's +/- 2 per second.

 

in cat III that dropped to

 

90 Degrees +/-2 per second.

 

in a clean aircraft at 1 degree AOA.

 

That seems like a 60% reduction not a 40% reduction and it may be because some one did the same mistake as I did when I was calculating just now in my testing.

 

225 * .4 = 90 but that's a 60% decrease.

225 * .6 = 135 which is a 40% decrease.

 

you can actually check this properly...

 

225 - 90 (40% of 225) = 135 not 90.

 

You can recreate this easily.

 

Load up a clean bird, take off get her level at about 400 - 500 knots. CAT I

Deflect the Aircraft full Left Stick in a roll you'll get the 225 etc rolll rate.

 

Select CAT III

reset up at 400 - 500 knots same altitude level do the deflection again.

you'll get 90ish roll rate.

 

Now maybe the limiter was increased in the 3 years difference to 60% but seems a little strange, and more likely some one's made a simple math error like I did above in the roll rate calcs which is causing the limiter to kick in slightly early.

[robgraham]

Track and Tacview Graph showing R/R first is CAT I second is CAT III

rollrate.trk

[LJQCN101]

DFLCS can command a maximum of 324 deg/s roll rate in cruise gains, but that's the command value in the FLCS and you usually won't achieve that aerodynamically.

 

Switching to CAT III will reduce the roll rate by 130, but the maximum roll rate reduction is limited to 244. That means in best cases you can command 324 - 130 = 194 deg/s, while in worst cases you can only command 324 - 224 = 80 deg/s.

 

That's what you can tell from the very-hard-to-read DFLCS control block diagram (ref DTIC ADA 189675). And the DFLCS modelled in DCS F-16CM may or may not have the same value.

 

[robgraham]

DFLCS can command a maximum of 324 deg/s roll rate in cruise gains, but that's the command value in the FLCS and you usually won't achieve that aerodynamically.

 

Switching to CAT III will reduce the roll rate by 130, but the maximum roll rate reduction is limited to 244. That means in best cases you can command 324 - 130 = 194 deg/s, while in worst cases you can only command 324 - 224 = 80 deg/s.

 

That's what you can tell from the very-hard-to-read DFLCS control block diagram (ref DTIC ADA 189675). And the DFLCS modelled in DCS F-16CM may or may not have the same value.

 

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LJ, that's why i listed as Possible bug, not confirmed because with out access to the FM and the like it's hard to tell, the issue is though that if you go to DFLCS limiter sections it lists the exact AOA limits etc for Pitch, Roll and Yaw under each category and how they come into effect eg pitch is G limit (9g) until 15 aoa then blends to stop anything over 25AOA roll has the same limits (I could type it all out but haven't slept due to pain tonight), CAT III pitch has a lower max aoa limit (18 AOA) but in the roll it simply states that it's a 40% reduction ontop (eg if it was 100 you'd be 60) of the CAT I limit, that's what I tested here.. the ROLL limit and it's giving a 60% reduction not a 40% reduction.. which seems like a possible math error.

 

the actual DFLCS block diagram is an interesting one because of the AMOUNT of inputs it comes in, I've played with modelling them in the past for another sim but left the company i was working for before i got too far into it (one of the reasons I like the 16 there are some nice NASA etc documents from when it was used for Digital Flight Control experiments ;) ).

 

But yeah I figured I'd mark it as a Possible bug and let Wags and the Dev's check the evidence etc, because the issue is as well different levels of documentation etc.. the DFLCS has had a number of changes even over short periods especially as ordiance loads etc were added, great example was when the CFT's were brought out they changed it's limits for those, etc..