Stick forces telemetry and stability testing

[Bucic]

1. Can the data (forces on all flight controls vs time;doesn't have to be a real-time acquisition) be exported from a test flight in DCS?

2. Is there a way to force hands off the stick (free movementof the control stick) (edit:) for non-FFB joystick?

 

Related

ForceFeedback in DCS - realistic or gimmick?

http://forums.eagle.ru/showthread.php?t=129387&highlight=hinge

 

EDIT:

Let's focus on aircraft with direct mechanical links, for the sake of clarity.

Edited August 5, 2015 by Bucic

[OnlyforDCS]

Im not sure I understand what you are asking but I will try to answer the second part of your question as I understand it.

 

I have the MS FFB2 stick, which I have modified slightly by taping off its grip sensors. Ive tested it a little bit, and the stick seems to move by itself due to the forces acting on it. When powering up, the stick will center itself as (from a full back locked tail-wheel position) as the airspeed increases. I have tried some hands-off maneuvers in the air and the stick seems to behave realistically. The forces get stronger as the airspeed increased and taper off near stall speed. On a badly executed landing the stick moved violently when my Mustang rolled over and I imagine the control surfaces were violently moved.

[SinusoidDelta]

This is something I'm curious about as well for the F-15C. What aircraft(s) are you referring to?

[Bucic]

This is something I'm curious about as well for the F-15C. What aircraft(s) are you referring to?

First and foremost to aircraft with direct mechanical links. If F-15 doesn't sport a force feedback system, all you'll get is just characteristics of the springs used.

[Bucic]

Im not sure I understand what you are asking but I will try to answer the second part of your question as I understand it.

 

I have the MS FFB2 stick, which I have modified slightly by taping off its grip sensors. Ive tested it a little bit, and the stick seems to move by itself due to the forces acting on it. When powering up, the stick will center itself as (from a full back locked tail-wheel position) as the airspeed increases. I have tried some hands-off maneuvers in the air and the stick seems to behave realistically. The forces get stronger as the airspeed increased and taper off near stall speed. On a badly executed landing the stick moved violently when my Mustang rolled over and I imagine the control surfaces were violently moved.

Your answer fits the other thread well. In fact it was the very test I was going to ask to be conducted by one of you FFB guys. So the neutrum floats around in complex maneuvering as I should. As for the question - I've just revised it.

[SinusoidDelta]

First and foremost to aircraft with direct mechanical links. If F-15 doesn't sport a force feedback system, all you'll get is just characteristics of the springs used.

 

I'm only familiar with F-15 flight control system which has direct hydro mechanical linkage to the control surfaces. The system uses a linear rate spring and jack screws to provide the same aircraft response regardless of airspeed. If the AFCM were perfect, the linear rate spring would be the only opposing force the pilot feels.

 

No FFB stick I know of is capable of simulating the F-15's spring rate which is something like 30 lbs. full aft. You'd be better off using a real spring than a virtual one. I'd imagine the stick would need anchored into the floor. Flying the Eagle would become a decent workout. ;)

[Bucic]

I'd be grateful for even a hint on the subject. Software, API, who mentioned it or in what circumstances it has been mentioned.

[SinusoidDelta]

I'm not sure what exactly you're looking for.

 

FFB was planned to be implemented in the F-15C AFM. (See thread below)

http://forums.eagle.ru/showthread.php?t=122788

 

There may be some parameters in the FM config to investigate.

[Bucic]

I'm not sure what exactly you're looking for.

 

FFB was planned to be implemented in the F-15C AFM. (See thread below)

http://forums.eagle.ru/showthread.php?t=122788

 

There may be some parameters in the FM config to investigate.

I meant what I wrote in the original post. You're going to have to state specifically what is not clear to you.

[SinusoidDelta]

A lengthier explanation of what you want to accomplish would be helpful, and for which aircraft. I don't know if every FM uses the same logic for stick input, obviously they don't in real life. Do you know if "flight control force" is some universal parameter in DCS?

 

Regardless, it doesn't seem like there is pre-made solution hence why no one can link you to a specific thread. Have you experimented with any files in DCSWorld\Scripts\Input?

 

Also:

In the Eagle if you take your hand off the stick it will stay centered which is why I don't understand the second portion of your question.

[Bucic]

A lengthier explanation of what you want to accomplish would be helpful, and for which aircraft. I don't know if every FM uses the same logic for stick input, obviously they don't in real life. Do you know if "flight control force" is some universal parameter in DCS?

 

Regardless, it doesn't seem like there is pre-made solution hence why no one can link you to a specific thread. Have you experimented with any files in DCSWorld\Scripts\Input?

 

Also:

In the Eagle if you take your hand off the stick it will stay centered which is why I don't understand the second portion of your question.

Let's focus on aircraft with direct mechanical links, please.

I don't know of any method I could bite into it. I don't have any experience with DCS FMs nor with LUA. I was rather hoping there's some debug mode I could use or there's something relevant in .trk files.

[Captain Orso]

Not to muddy the waters, but the first aircraft I think of with direct stick-to-control-surface controls are the WWII war birds.

 

My take on these is that commercial FFB will never be able to simulate the forces working on the stack by airflow over the control surfaces. You would need a system which could exert a force so strong on the stick that a strong, healthy individual could not move the stick more than a couple of centimeters in certain situations--a high speed dive for example.

 

FFB can only give you some inkling as to the force on the stick, but never near reality.

[Captain Orso]

The force would be scaled down within the posibilities of the joystick, of course.

 

To gain the actual meaning of the affects of air pressure on the control surfaces that is actually what would have to happen.

 

In a thread about how to setup stick-curves somebody noted that in Reality™ in flight at combat speed a pilot cannot actually move the stick as far as he could while sitting on the ground and that therefore to be realistic one should setup the curves so that they stop motion beyond about 30-50% of full motion.

 

A FFB-like system could reduce the motion range automatically depending on speed, but it would not correspond to the actual stick position. If it were setup so that the control surfaces and the stick maintained a 1-1 relationship, but the control surfaces simply stopped extending after hitting for example 50%--depending on the speed--while the stick kept moving, that would simulate the freedom of motion, but the pilot would not experience the force necessary to get that far or that he cannot actually push beyond that motion.

 

If the FFB-system adjusted the amount of motion of the control surfaces depending on speed so that for example at 400MPH the elevators could only be pulled back to 30%, but the stick were pulled back 100% then the constant change in the affects of positioning the stick relative to speed would make it nearly impossible to fly with any amount of control; the pilot would always be searching for how affective his stick were at any given time :joystick:.

 

So I see no really good solution, but using the first example FFB could at least give the virtual-pilot a warning that the stick has reached its maximum at a given speed.

 

If I'm understanding it correctly, the question is if the FM's in DCSW generate data about the aerodynamic forces on the control surface and if this data is used to program the FFB.

 

My guess is that in DCSW FFB isn't programmed like that and is simpler. Things like scaling the spring force with the IAS, playing a sine wave while stalling and the like.

 

If that's that's case it's actually too bad.

[Oydoron]

To gain the actual meaning of the affects of air pressure on the control surfaces that is actually what would have to happen.

 

And so long as only a small fraction of users have access to FFB, there is no motivation to add that to the engine.

[OnlyforDCS]

 

So I see no really good solution, but using the first example FFB could at least give the virtual-pilot a warning that the stick has reached its maximum at a given speed.

 

 

Well I know the forces acting on my FFB stick are approximations, and scaled down ones at that. But they are still the next best thing to a commercial simulator or the real thing. You DO get indications of how much you can pull on the stick and the forces do increase significantly at speed.

 

If you think DCS calculates forces on the fly for the FM you would also be mistaken. (You would need a supercomputer to run that)

 

Some modules (like the ED Bf109 Kurfurst) apparently even have a software limitation build in, so your 'virtual' stick locks and behaves exactly like in the real plane (it simulates the extreme pressures on the control surfaces). SInce I dont have the K4 module (YET) and I missed the last sale I can't test whether the FFB motors on my joystick would lock up in those circumstances.

 

If anyone wants to donate a K4 key I could test that later today :music_whistling:

Edited August 7, 2015 by OnlyforDCS

[Bucic]

Guys, please, this is not a thread on FFB. I expect it's going to be difficult enough to get the info even without thread hijacking. Feel free to use the other thread I've linked in the original post. As for the implementation for K4, there's also a separate multi-page for that.