FFB Stick for F15E?

[Alpha]

If I understand you correctly we´re both saying about the same: stick forces in the Strike are pretty much constant per G through the flight envelope and while most of the (pitch) trimming seems to be handled by the FCS the pilot can and will trim any "out of center" trim position back to center. 

 

That´s why I think one will benefit very little from a FFB-stick at home. A FFB-Stick is nice for "Cessna-types", any old props, some smaller jets as they have very different / changing stick forces depending (mostly) on airspeed. Modern fighters with hydraulically powered flight controls don´t really behave like that. I´ve never flown an Eagle, but the difference was obvious changing from the T-37 to the T-38:

In the T-37 you had flight controls connected to the stick via cables and pulleys - you could feels the air loads an the control surfaces, stick forces were not "constant-ish" at all. 

In the T-38 with it´s hydraulically powered flight controls the stick forces didn´t change like that - the sensitivity did (rather sluggish pitch at slow speeds, rather fickle pitch at high speeds). 

 

The way I understand the references given above the F-15E should be like that and in addition the sensitivity is mangaged by the FCS so that a given stick force (pitch) of about 4.25lbs should pretty much always be required for "one more G - worth of pull" (the edges of the envelope are explained in more detail in the given references). In simple terms: you pull 4.25lbs, you´re commanding one additional G . You pull 8.5lbs, you get two G and so forth.

 

Additionally the Microsoft Stick (and the G940, which I tried many moons ago) are nowhere as close to the real HOTAS-Layout as TM´s Warthog etc.  In the End it´s all personal preference - just don´t expect a modern fighter to have the "slow speed = wobbly, soft stick forces, high speed = heavy stick forces" - behavior that props / old jets without hydraulic flight controls do...

Edited March 1, 2023 by Alpha

[Rainmaker]

4 hours ago, Alpha said:

If I understand you correctly we´re both saying about the same: stick forces in the Strike are pretty much constant per G through the flight envelope and while most of the (pitch) trimming seems to be handled by the FCS the pilot can and will trim any "out of center" trim position back to center. 

 

That´s why I think one will benefit very little from a FFB-stick at home. A FFB-Stick is nice for "Cessna-types", any old props, some smaller jets as they have very different / changing stick forces depending (mostly) on airspeed. Modern fighters with hydraulically powered flight controls don´t really behave like that. I´ve never flown an Eagle, but the difference was obvious changing from the T-37 to the T-38:

In the T-37 you had flight controls connected to the stick via cables and pulleys - you could feels the air loads an the control surfaces, stick forces were not "constant-ish" at all. 

In the T-38 with it´s hydraulically powered flight controls the stick forces didn´t change like that - the sensitivity did (rather sluggish pitch at slow speeds, rather fickle pitch at high speeds). 

 

The way I understand the references given above the F-15E should be like that and in addition the sensitivity is mangaged by the FCS so that a given stick force (pitch) of about 4.25lbs should pretty much always be required for "one more G - worth of pull" (the edges of the envelope are explained in more detail in the given references). In simple terms: you pull 4.25lbs, you´re commanding one additional G . You pull 8.5lbs, you get two G and so forth.

 

Additionally the Microsoft Stick (and the G940, which I tried many moons ago) are nowhere as close to the real HOTAS-Layout as TM´s Warthog etc.  In the End it´s all personal preference - just don´t expect a modern fighter to have the "slow speed = wobbly, soft stick forces, high speed = heavy stick forces" - behavior that props / old jets without hydraulic flight controls do...

 

No, we were not saying the same things.  Stick pos is physically trimmed from center when the trim hat is used. 
 

As for force changes, there is just an example of where stick force changes and is not constant. 

[MAXsenna]

@alpha

One can "easily" mod the MS FFB2 to use other grips. The best part with it being FFB is the ease of trimming, because you just pull to you're "trimmed", and then trim with the hat until you don't need to pull anymore.

Cheers!

Sent from my MAR-LX1A using Tapatalk

[Alpha]

@Rainmaker: So, are the references provided incorrect? They explicitly mention:

"Remember, the Eagle flys at essentially a constant stick position for a given g." (https://www.f15sim.com/operation/f15_flight_control_system.htm)

"The combination of feel trim, variable mechanical advantage, and series trimming gives the pilot, as near as possible, a constant stick force per G and keeps the stick pretty well in the same place in the cockpit throughout the flight." (https://www.f15sim.com/operation/f15_hydro_mech.html)

Stick-Force per Deflection and per G:  https://imgur.com/a/qnyrpD0

"This provides the same pitch response (constant G) for a given stick deflection regardless of airspeed." (TO 1F-15A-1, 1-28)

"When airborne, the flight control system automatically trims the stabilator without affecting stick position to compensate for changes in trim caused by such things as changing speed, operating flaps or speed brake, or store separations." (same) Manual trim does move the neutral stick position - but that should happen when there´s an out-of-neutral position not covered by the automatic trim so the resetting of the neutral point should bring it back to where it was/should be while in-trim...   That´s why I think we´re really saying the same.

 

"Pitch response to stick input does not vary appreciably with airspeed, altitude, engine power, or configuration change" (6-1 of the Dash 1). 

 

That sounds not at all like the varying stick forces you get in your local C172 or any aircraft with unpowered flight controls. The Phantom, for example, has noticably different stick forces at different speeds (because those forces are introduced artifically by a speed-dependant system), the Eagles description doesn´t sound much like that. 

 

Edited March 1, 2023 by Alpha

[MAXsenna]

Don't know about the SE, but the FC3 F-15C moves the stick when you trim. Just tested.

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[Alpha]

Yeah, that´s correct as per the system description when using manual trim. It resets the neutral point, thereby changing the (unwanted) forces at the current stick position. Changing the position of the neutral point is just a way to changing the forces at it´s current position (trimming required out-of-trim stick forces away).

 

Obviously the stick would only move during manual trim if you´d let go of it. IRL you have the stick in your hand and notice a continuous, unwanted stick force due to being out-of-trim - and therefore you´d trim manually. So the stick doesn´t change position but the forces you experience while holding it at it´s correct position change (there´s a ton of "sts" in those sentences...    ).

 

My question would be how often this is required in Flight in a real F15. The system desciptions all point at a rather automatic trim system with little manual trim input required. Not "none", but rather little.

Edited March 1, 2023 by Alpha

[MAXsenna]

@alpha
Ah! I see, that makes sense, and also why FFB in sims makes sense.

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[Rainmaker]

52 minutes ago, Alpha said:

Yeah, that´s correct as per the system description when using manual trim. It resets the neutral point, thereby changing the (unwanted) forces at the current stick position. Changing the position of the neutral point is just a way to changing the forces at it´s current position (trimming required out-of-trim stick forces away).

 

Obviously the stick would only move during manual trim if you´d let go of it. IRL you have the stick in your hand and notice a continuous, unwanted stick force due to being out-of-trim - and therefore you´d trim manually. So the stick doesn´t change position but the forces you experience while holding it at it´s correct position change (there´s a ton of "sts" in those sentences...    ).

 

My question would be how often this is required in Flight in a real F15. The system desciptions all point at a rather automatic trim system with little manual trim input required. Not "none", but rather little.

 

No, its not incorrect, you are just misinterpreting what it’s saying. 
 

T/O trim moves stick pos

cancelling T/O trim moves stick pos

Any manual trim moves stick pos. 
 

PTC trims to 1.0 G longitudinal. Does not trim in roll. Asymmetric loading can require manual trim. Etc etc

Stick force is not always constant.  There are scenarios where it changes I listed one of those  etc  

The DCS C’s FM is a good representation of this. 

[Alpha]

Can you be more specific as to what is wrong from your point of view?

 

We were only talking about pitch trim, not T/O Trim or Aileron trim. 

 

7 minutes ago, Rainmaker said:

Any manual trim moves stick pos. 

It moves the neutral point. Stick position only depends on where the pilot puts it. He trims (if required) to not have to fight the out-of-trim. This is achieved by moving the neutral point.

 

10 minutes ago, Rainmaker said:

Stick force is not always constant.  There are scenarios where it changes I listed one of those  etc  

Nobody said that. See the pictures and references given above. The -1 is pretty clear on this. 

 

The only question really is as to how much the manual trim needs to be used in Flight IRL despite the obvious effort of the FCS to keep this to a minimum. 

[Rainmaker]

11 minutes ago, Alpha said:

Can you be more specific as to what is wrong from your point of view?

 

We were only talking about pitch trim, not T/O Trim or Aileron trim. 

 

It moves the neutral point. Stick position only depends on where the pilot puts it. He trims (if required) to not have to fight the out-of-trim. This is achieved by moving the neutral point.

 

Nobody said that. See the pictures and references given above. The -1 is pretty clear on this. 

 

The only question really is as to how much the manual trim needs to be used in Flight IRL despite the obvious effort of the FCS to keep this to a minimum. 

Lol. I know what the -1 says.  I know what most of it says. I worked E models for a lot of years.  I’m aware of how the system works and have real life experience with it. I have given you feedback already. I’m not going to keep dragging this out over and over.  You keep trying to narrow the scope and move the needle all around.  
 

Your original post I quoted is below. A lot of things ‘not correct’ with it which I told you about already.  Now we are excluding things, etc. Not playing the silly games. 
 

‘As mentioned before: the Stick forces in the real F-15E are linear force per G and do not change with Airspeed. The stick position also doesn't change while trimming (see links above). There's really no point in FFB with the Strike Eagle.’

 

 

Edited March 1, 2023 by Rainmaker

[Alpha]

Well, then just work with us, this is not a contest. I´ve given multiple quotes above, including the official "Handbook", the -1. It says: "This provides the same pitch response (constant G) for a given stick deflection regardless of airspeed."  And it says "Because of the automatic trim feature, the stick force required to maintain a desired g does not change with airspeed or configuration change." 

 

Also there´s a huge difference between "stick position" and "neutral point", as explained above. This system of changing the neutral point as rather common - I´ve flown military jets and airliners with a similar system.

 

The constant stick force per G is explicitly mentioned in the system desciption I linked and quoted above. There´s even a graphic representation of it. So clearly just saying "it´s wrong" doesn´t cut it. So don´t get defensive but explain what´s wrong from your point of view. 

Edited March 1, 2023 by Alpha

[MudMoverGSH]

Although as mentioned by others above that the sticks of the Eagles are not like the "conventional" plane such as C172/Warbirds, where the stick force is affected by the changing of airspeed etc, I still think an FFB-base is superior to the spring-base even in this use case for the following reasons:

1. asymmetric stick travel could be easily achieved via the configuration software. Most(?) aircraft have asymmetric travel btwn pitch and roll and even btwn push and pull. You can't emulate that for a spring-base without physically modding it.

2. Although the consumer FFB-bases are as weak as the best spring-bases in terms of stick force, some half-DIY kits can use much stronger motors to provide better if not true-to-life forces. Of course you can buff up springs with mods for the spring-bases but...

3. Of course, you'll need the FFB to simulate the manual trim and T/O Trim etc where the trim actuator moves the stick(or as a result, hold the stick against the unwanted stick force that keeps trying to center it).

4. FFB bases might provide better damper simulation. Some dampening solutions for the spring-bases might introduce unwanted stiction, play and other unwanted side effects,  and might require fine-tuning, especially when using heavier springs.

5. For spring-bases, "curves" are determined by the shape of the cams which are almost impossible to change and I believe those currently available are not 100% ideal for simulating the real thing; whereas for FFB-bases, curves/profiles can be easily reprogrammed via software to suit the model you fly. This is especially helpful when you have multiple different types of models to fly, such as FBWer/Warbirds/Helo; swapping btwn them when using a spring-base is a headache.

 

That said, I'm all against ditching HOTAS for old FFBs like those from MS or Logitech when flying modern aircraft. HOTAS is even more important for a realistic experience IMO, especially when lots of "modern" jets themselves mainly rely on spring&cam plus dampers to provide physical feedback. And there are the stick extensions that the old FFBs can't use.

Then modern FFBs that can use "HOTAS grips" are the ways to go. But I've heard the Brunner has an aggressive cooling strategy that could ruin the experience of dog fighting, and it's way expensive and IMO overpriced. I'd suggest looking for something like VPForce (Rhino base or DIY motors&PCB kits), LaserWing, or DIY out of some opensource solutions.

 

PS: IIRC, I've read somewhere(either the manual or a book of flight control system) that the contemporary F-14 also features a feel system that only consists of springs, cams, dampers and bobweights; and the hydraulic(hydromechanical?) control system is only 1-way, i.e. doesn't provide any physical feedback from the control surface to the control stick(&rudder pedals).

Edited March 6, 2023 by MudMoverGSH

[MudMoverGSH]

On 3/2/2023 at 2:03 AM, Alpha said:

It moves the neutral point. Stick position only depends on where the pilot puts it. He trims (if required) to not have to fight the out-of-trim. This is achieved by moving the neutral point.

Quote from TO 1F-15E-1:

Longitudinal Trim/Feel System

...The manual trim actuator changes the neutral position of the longitudinal feel spring cartridge to reposition neutral stick position and thus neutral stabilator position. When airborne the flight control system automatically trims the stabilator without affecting stick position to compensate for changes in trim caused by such things as changing speed, operating flaps or speed brake, or store separations...

 

So my understanding is, since the spring is always trying to centering the stick, moving the neutral position will result in moving the stick position? For manual trim of course.

[Alpha]

Hi MudMoverGSH. I agree with your view on FF as mentioned in your first Post. There is some gain in realism - it´s just not as big as with aircraft where one can feel airloads on control surfaces. Also your point on HOTAS vs FF is spot on from my point of view. In the end it´s all personal preference, I guess (I´d recommend a good HOTAS Setup and some sort of jetpad/buttkicker - most feedback in military jets come via burble from the wings impinging on the stabilator/airframe and you feel it via the structure/seat, hardly via the stick. "Pull to the light tickle", "mice vs elephants dancing on the wings" etc are all in reference to that.)

 

On the trim: Moving the neutral position would mean moving the stick if nobody held it in the desired position, yes. As the pilot usually holds the stick you just feel the forces change. Example: you feel the jet being nose-heavy. Now you start trimming back, the neutral point is shifted and therefore the forces at the current stick position change towards "tail heavy" - compensating the prior, unwanted "nose heavy". At the right trim amount you can now let go of the stick and the jet remains trimmed with the stick not moving when you let it go. It´s a bit cumbersome to explain, sorry  

 

That system/logic is widely used, even in airliners (talking non-FBW and usually aileron trim only. Pitch trimming is done via moving the stabilator). There you could trim the aileron while the autopilot has control - which completely masks the trim change as the autopilot is "the hand on the stick" in that case. If you´d now disengage autopilot you´d suddenly get back an out-of-trim aircraft  and you couldn´t see that before as the yoke doesn´t move (That´s why manually trimming control surfaces with a moving neutral point is forbidden and results in an EICAS indication). 

 

 

Edited March 5, 2023 by Alpha

[MudMoverGSH]

4 hours ago, Alpha said:

Hi MudMoverGSH. I agree with your view on FF as mentioned in your first Post. There is some gain in realism - it´s just not as big as with aircraft where one can feel airloads on control surfaces. Also your point on HOTAS vs FF is spot on from my point of view. In the end it´s all personal preference, I guess (I´d recommend a good HOTAS Setup and some sort of jetpad/buttkicker - most feedback in military jets come via burble from the wings impinging on the stabilator/airframe and you feel it via the structure/seat, hardly via the stick. "Pull to the light tickle", "mice vs elephants dancing on the wings" etc are all in reference to that.)

 

On the trim: Moving the neutral position would mean moving the stick if nobody held it in the desired position, yes. As the pilot usually holds the stick you just feel the forces change. Example: you feel the jet being nose-heavy. Now you start trimming back, the neutral point is shifted and therefore the forces at the current stick position change towards "tail heavy" - compensating the prior, unwanted "nose heavy". At the right trim amount you can now let go of the stick and the jet remains trimmed with the stick not moving when you let it go. It´s a bit cumbersome to explain, sorry  

 

That system/logic is widely used, even in airliners (talking non-FBW and usually aileron trim only. Pitch trimming is done via moving the stabilator). There you could trim the aileron while the autopilot has control - which completely masks the trim change as the autopilot is "the hand on the stick" in that case. If you´d now disengage autopilot you´d suddenly get back an out-of-trim aircraft  and you couldn´t see that before as the yoke doesn´t move (That´s why manually trimming control surfaces with a moving neutral point is forbidden and results in an EICAS indication). 

 

 

 

Hi Alpha. Oh yeah, indeed, usually in flight, the manual trim is for "holding" the stick, not necessarily moving it, since in that case the stick is already moved by the pilot's hand to hold a position away from the "absolute center" of the travel in order to maintain a certain attitude. I only have experience IRL on GA planes but it sounds to me that the manual trimming behavior of the stick for the non-full-FBW jets is in a sense similar to the GA one. (IIRC the 18 is different in "normal" mode where there is no trim actuator to hold/move the stick but the trim actuator will kick in once in "backup" mode and it'll behave in the "traditional" way.) And in other words, if you move the trim switch on the ground where the stick force is zero, it will actually move the stick, right?

 

Good point on the trimming vs AP. Never thought about it that way. I think it might be the reason why the engineer usually connects the AP actuator to the stick/yoke while letting the trim actuator move the feel and centering device.

 

 

I forgot to mention the jetpad/buttkicker in the earlier post. Totally agree with your point on it, as the vibration is from the airframe, not the aerodynamic effects relayed by the stick. Stick with stick shaker on it or buttkicker under it is a more natural way to replicate it. And I think it's better to not only make the stick shaking, but also have the butt kicked via buttkicker and/or jetpad, otherwise it would be very odd.

 

[erniedaoage]

13 hours ago, Alpha said:

On the trim: Moving the neutral position would mean moving the stick if nobody held it in the desired position, yes. As the pilot usually holds the stick you just feel the forces change. Example: you feel the jet being nose-heavy. Now you start trimming back, the neutral point is shifted and therefore the forces at the current stick position change towards "tail heavy" - compensating the prior, unwanted "nose heavy". At the right trim amount you can now let go of the stick and the jet remains trimmed with the stick not moving when you let it go. It´s a bit cumbersome to explain, sorry  

That is the point everybody was talking about before and where the misunderstanding kept happening, that the stick moves its neutral position and its physical position in the cockpit and if you got a ffb stick the stick will move with it. That's one basic feature for forcefeedback which is not working with any razbam module, even if you see the stick moving in the cockpit, my stick stays centered all the time. My next problem is that with every other module with ffb, the stick feels different. I know that there is a huge difference between a ww2 tail dragger with direct control of the surfaces and  a jet with a hydraulic system. But all i feel in razbam modules is the same force all the time like a normal joystick with a spring. I have the M2000c (which i don't like cause it's fly by wire, thats also why i don't like the f18 but i haven't known it till i've flown it), the Harrier and the MiG-19 and all feel the same on the stick and i haven't flown any of them longer than probably an hour in all the years since their release. 

I am not going to buy another razbam module as long as i am not able to enjoy the harrier and mig19.