Mainly for Mav-JP - 12 degrees stick axes offset
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I worked the F-16 for 19 years and never heard of this and also just double checked the FLCS CDCs. They don’t mention one word about FLCS adjustments for engine gyroscopic effect. The only adjustment it talks about for outside influences like this is the gun compensation logic.
On a hard pitch command, if engine gyroscopic does effected the a/c it would be yaw if anything. This would create an outside influences in the yaw rate sensors, lateral acceleration and ADC. The same component that corrects for Dutch roll would try to correct of gyroscopic yaw. As everybody knows when you step on the peddles there is some roll (blank) not corrected by the FLCS.
Engine torque from delta rpms is another thing.
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On a hard pitch command, if engine gyroscopic does effected the a/c it would be yaw if anything.
Hence why I don’t believe the effect is enough to alter course. If it were there would have to be compensation logic built into the FLCS based on RPM. If there were it is subject to errors and fails like any other electronic system in the aircraft so it would be talked about and explained in the CDCs, fault manuals, etc. I haven’t seen a thing and before today never even heard of this for the F-16.
The same component that corrects for Dutch roll would try to correct of gyroscopic yaw.
That would be the ARI helping to coordinate turns in the F-16. The only way you could use the same logic would be if the required yaw input would be the same or some relation/ratio could be developed between the two. It would also have to work in conjunction with the ARI for normal turns. Once again gyroscopic engine flight path correction is not mentioned at any point for the F-16.
As everybody knows when you step on the peddles there is some roll (blank) not corrected by the FLCS.
Correct. The system alters on rolls for adverse yaw (ARI or the “Dutch roll” as you put it) but not on yawing for roll effect.
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I could not tell you anything about FLCS, DFLCS programing, etc. I have no idea how all works. I can not account for all FLCS/DFLCS corrections, but I never heard of gyroscopic engine effects affecting the F-16. Could it be there? Sure. I just never heard of pilot write up a F-16 for it rolling due to quick changes in RPM. I have trouble shoot many taxi “aircraft pull to the right” discrepancies. But they where caused by brakes, NWS, landing gear servicing, TGP, pilots and the NLG design. (wish according to the -1 could cause this effect dues to the " single fork" design of the NLG.
The single fork design of the NLG causes the
aircraft to drift right when NWS is not engaged. This
drift is easily controlled with rudder or differential braking.
Applying forward stick force during landing roll increases the
load on the nose wheel which increases the
right drift.In relation to the stick being rotated, never noticed, that is interesting.
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That would be the ARI helping to coordinate turns in the F-16. The only way you could use the same logic would be if the required yaw input would be the same or some relation/ratio could be developed between the two. It would also have to work in conjunction with the ARI for normal turns. Once again gyroscopic engine flight path correction is not mentioned at any point for the F-16.
Correct. The system alters on rolls for adverse yaw (ARI or the “Dutch roll” as you put it) but not on yawing for roll effect.
I believe that ARI adds rudder to aileron inputs. No feed back loop.
To correct the Dutch roll, feedback from external and internal sensors is used to augment the rudder.
It’s the same component that corrects for slip/slide in a turn and allows the pilot to turn without using the rudder peddles.
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In relation to the stick being rotated, never noticed, that is interesting.
let met get you up to speed.
They’re saying that stick sensors are rotated and not the grip handle for 3 reasons I guess. (There is a pic that looks photoshoped.)
1. arm geometry
2. easier to pull the stick when it rotated to the pilot. But some ppl believe that if that was the case the grip handle would also be rotated.
3. and my lame idea, it mixes roll command when a pitch command is made.Nobody can find any r/l doc giving a reason why the sensor assy. is rotated.
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I worked the F-16 for 19 years and never heard of this and also just double checked the FLCS CDCs. They don’t mention one word about FLCS adjustments for engine gyroscopic effect. The only adjustment it talks about for outside influences like this is the gun compensation logic.
there is a roll rate feedback in the FLCS, so there is compensation for it.
Gyroscopic effect is very small (read NASA TP 1518), i decided not to include it, because the only value that i have is for 1 regime of engine and i dont know the correlation between engine rpm and gyroscopic effect
it is very very small effect though , just forget about it.
That does not answer my question; if you put roll , will it mix it with pich as well ?
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I believe that ARI adds rudder to aileron inputs. No feed back loop.
To correct the Dutch roll, feedback from external and internal sensors is used to augment the rudder.
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/DutchRollAnimGIF02.gif/200px-DutchRollAnimGIF02.gifIt’s the same component that corrects for slip/slide in a turn and allows the pilot to turn without using the rudder peddles.
if you read the FLCS article available on this website, you wont discuss all of this
page 29 you clearly see the SAS
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if you read the FLCS article available on this website, you wont discuss all of this
page 29 you clearly see the SAS
does your ARI work in the clocks?
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That does not answer my question; if you put roll , will it mix it with pich as well ?
welp, sometimes in design and r/l you have to choose the lesser of the two evils.
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What I’ve read about the gyroscopic effect is that it is small, I think that the Harrier engine was designed to counter this effect, blades turning in opposite directions or similar, to have more stability during hovering.
Cheers
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oops,
does your ARI work in the chocks? -
oops,
does your ARI work in the chocks?ARI is not active in WOW because alphalag is nulled
ARI is active when not in WOW and alpha < 29 and Wheelspeed < 60 kt ( this is to be sure to disconnect ARI during aerobraking and at take off phases, pretty clever isnt it )
At take off, ARI is not active until wheels have slow down to 60 kt, you can accelerate the ARI kick in by braking the wheels in Air …and yes this is simulated in BMS because BMS FLCS = REAL
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What I’ve read about the gyroscopic effect is that it is small, I think that the Harrier engine was designed to counter this effect, blades turning in opposite directions or similar, to have more stability during hovering.
Cheers
Yeah, its mentioned here
http://www.flightglobal.com/pdfarchive/view/1960/1960%20-%201299.html
and you can see that the low pressure section would turn counter clockwise, and the HP section turns clockwise, looking toward the front of the engine. Pretty neat, didn’t know about that.
http://upload.wikimedia.org/wikipedia/commons/1/15/Aircraft_engine_RR_Pegasus_cut-out_RH.jpg
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Hey Arty, good, fast and sleak solution there, thats also a way to do it cool.
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That does not answer my question; if you put roll , will it mix it with pich as well ?
Mav, I can confirm that the axes remain perpendicular to each other, as shown in the schematics posted before.
The source for this information is the same guy from F-16.net who turned out to be a structural flight test engineer for General Dynamics on the YF-16 and F-16 programs from 1973 until 1985. I addition I have seen at viperpits a foxy screenshot of the real SSC which shows not only the pitch axis but the roll as well and it´s offset to the horizontal and perpendicular to the pitch axis.
I hope this answers you.
Cheers
Tulkas
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hey arty, why only 6 degrees?
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hey arty, why only 6 degrees?
6??? in the pic it’s above 10… and if u put the instrument in the correct position it’s almost at 12.