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Pitch Trim Panel and System Discussion

(Original thread started on 06-06-14 by Eric Tomlin)

Ron and I are co-developing the Pitch Trim Controller panel. Per usual, Ron is handling the hardware portion of the panel while I handle the front back-lit panel. More information will be available soon on pricing. Please let us know as soon as possible if you are interested in one of these, as the components are not widely distributed and availability may be limited:

Eric 47


(Posted by Ron Rollo on 06-08-14)

Thanks for all the positive responses to this panel and the cooperation.  The Pitch Trim Panel is fairly easy, however, just to give you guys a heads up, the hardware on this panel is a bit pricey. As an example, the three position rotary that snaps back to center is almost $60, and the pitch switch is almost $30. I am also going to make and include the knobs so you guys will not have to worry about them.


Before we take any solid orders, we will complete one prototype and fine tune what the cost will be for the end users.


(Posted by Shane Barnes on 06-08-14)

Great work Ron and Eric. I should be getting the double pole center toggle switch in Wednesday to ensure that it will work as planned to allow switching between primary trim on the yokes and secondary trim on the center pedestal. Will update once the switch arrives.


(Posted by Ron Rollo on 06-27-14)

The Pitch Trim Panel is coming along nicely and I will be posting some photos of the prototype in the next day or two. Eric and I will be offering this panel in a "Do it yourself" package and a "Plug and Play" version. The main reason I want to offer this panel in a DIY package is because of the cost of the hardware. I don't want you guys to kill over from sticker shock!


With that said I want to post up a few links to the specialty hardware that is needed for this panel so that we have it on record.


Three Position Toggle:  It turns out that you will need a 4 pole switch rather than a 2 pole.  You will need the 4TL1-1A, 4 pole, 3 position switch.  The reason being is we need a third pole to tell the InterfaceIT software what position the switch is in.  Any time that the switch is moved, it will disengage the autopilot just like the real aircraft.  They do not make a 3 pole switch so the only option was a 4 pole.  You can find an example of a 4TL1-1A Honeywell switch at Galco  HERE

Ron 1068


Pitch Trim Switch: This switch is actually a four way hat switch, (only forward and aft are used), part #679-2289-ND.  Keep in mind that the "hat switch knob" has to be cut off and a hole has to be drilled into the center of what is left of the shaft. Once that is complete, the slider knob that I make will press into the hole in the shaft. (I have said a million times that nothing about this project is easy right?) You can find a good example of the pitch trim switch at Digi-Key  HERE

Ron 1069


Rudder Trim Selector Rotary: This switch can be found at Online Components, E3G0603N-2.  What makes this piece of hardware rare and expensive is that it has a mechanism that returns the knob back to center.  You can find these at Online Components HERE

Ron 1070


So as you can see, just these three pieces of hardware is over $125 not including shipping.  A big thanks to Shane for finding these three key pieces of hardware for us!


UPDATE: Here is the price list of both the Pitch Trim Panel Kit and the Plug and Play:

The kit will include Eric's front panel, my backer panel, nylon standoffs, pitch trim retention ring, pitch trim knob, rudder trim knob, rudder trim plate and the screws to hold your panel to the backer. This package will not include the three main pieces of hardware that you would need to supply yourself.


The kit will run $60 plus Eric's front panel $135 = $195


The Plug and Play version will run $260 plus Eric's front Panel $135 = $395

The plug and play will include Eric's front panel, all the hardware and wiring harness for the FDS interfaces.


(There will be a little extra wiring to a relay depending on how far along you are. We will post up a wiring diagram shortly)


At this time if your interested in placing an order you can either make it known in this thread or by emailing either myself or Eric. We will give it about a week so that I can order all the major hardware at once:

Ron 1071


Ron 1072


As for the wiring diagram, let me first explain what the real trim system in the Lear45 does so that you can see why we need a double pole toggle and a relay. Shane and I were talking about this a few weeks ago and at this time we both decided to use hardware logic rather than software logic to emulate the Lear45 trim system. Software logic would be a better solution by far but only if Jet45AAS is updated with CAS messages and offsets related to the trim system. Until then, hardware logic it is.


The Lear45 trim system in a nut shell consist of four systems:






ROLL TRIM is controlled by the CWTS (Control Wheel Trim Switch) left and right on both the CAPT and FO yokes. The CWTS is a four way hat switch with a center push that has to be pressed to activate any of the four movements of trim including the pitch (up and down) trim. The CAPT's side CWTS overrides the FO CWTS in case there is a battle between the two pilots of where the trim should be set. There are no CAS messages associated with the roll trim and no secondary roll trim system.


Rudder trim is controlled by the RUDDER TRIM selector rotary on the PITH TRIM PANEL. There are no CAS messages associated with the roll trim and no secondary rudder trim system.


PITCH TRIM is a little more complicated because it is used 10 times more than the other two axis combined. The pitch trim system consist of two separate systems, Primary and Secondary and are even divide up on two separate electrical buses. The PRI PITCH TRIM is found on the CAPT and FO CWTS and will only operate if the center push button on the switch is depressed AND, the the three way toggle switch on the PITCH TRIM Panel is selected to PRI. This is the primary pitch trim system and the pitch trim should normally always be in this setting. If PRI is selected, no CAS messages will appear as long as there are no faults or failures.


The pitch trim back up system is the SEC or secondary pitch trim. The secondary pitch trim is found on the PITCH TRIM PANEL. It can only be operated if the three way toggle is selected to SEC. This deactivates the primary pitch trim system and also generates a CAS message (SEC PITCH TRIM).


Last but not least, if the three way toggle is selected to OFF, neither the PRI nor the SEC pitch trim system will work and the CAS message (PITCH TRIM OFF) will appear. There are at least twelve CAS messages associated with the trim system, most of them FAILs or FAULTs. JET45AAS has a few of them already including TAKE OFF TRIM.


In addition to all this the MSW (Control Wheel Master Switch) on each of the yokes will deselect all of the trim systems to protect against runaway trim systems which would be very bad. The MSW also deselects the autopilot and a host of other automatic systems that basically puts the aircraft back into manual flight control.


Now that the operation of the real Pitch Trim system has been covered in detail we can cover what is possible in our sims using hardware logic while still trying to keep things simple. After all, we would never touch the pitch trim panel during normal flight and operations. But it will be cool to demonstrate it's capabilities.


Most of us are using or are planning on using FDS interface cards. These are great cards more so because of the InterfaeIT software that comes with it that enables us to do all kinds of neat things with the hardware and LEDs. With that said, there are two cons that come with the FDS cards. The first being that they do not support encoders which is not a factor with the Pitch Trim Panel. The second con is the way the cards have to work using one common ground for each set of eight inputs. This is not a big deal either other than causing minor inconveniences, like here with the pitch trim panel.


Because of the way our FDS cards utilize one ground for every set of eight, it causes areas of the sim to be hardware isolated from other areas. As an example, the yokes. Each yoke uses one set of 8 inputs to 1 ground. This makes for a neat wiring harness, however, because we can not mix a common ground from one set of eight to the next, this causes us to have to keep each and every common ground isolated from one another.


Hopefully your seeing where the issue is if we want to move the toggle on the pitch trim panel from PRI to either SEC or OFF. So the way to keep these two grounds separated when we make a break in them is to use a double pole relay. We will use 12 volts to open and close the relay using the toggle. Then the ground lines for JUST the CWTS switches will be ran to each of the poles on the relay. (I say JUST because we only want the ground line running to the CWTS to be broken, NOT the ground for the entire group of eight inputs. If you did that, nothing on your yokes would work when you moved the toggle out of PRI.) This will keep the grounds isolated which will keep the FDS card happy.


The same problem is true keeping the PRI ground(s) separated from the SEC ground. To solve this part of the problem we need the double pole three position toggle switch on the pitch trim panel. Each pole on the toggle will keep the SEC ground isolated from the PRI ground. A wiring diagram coming soon will help illustrate this.


What are we not going to see operate correctly using hardware logic like this? First, there will be no CAS messages. But your not missing anything until JET45AAS is updated and this part of the build has not even been discussed with Jason Hite yet.


The other issue is when SEC is selected, we will be killing the PRI pitch at the CWTS including the ROLL trim. I have no idea how to separate the two because both the roll and the primary pitch are safety checked by way of the center push button on the CWTS. This is another good reason why software logic will be the superior way to go especially if JET45AAS is updated.


I will be wiring my pitch system up with the thoughts of using software logic in the future. But for now, I will be happy with using this bit of hardware logic.


(Posted by Alan Norris on 06-30-14)

There are ways of ensuring that an action such as an offset triggered by a switch cannot be executed unless another switch (and offset) is in either the ON or OFF position. For an example the START/RUN switch on the APU should not be able to operate until the APU MSTR switch is in the down position. Unfortunately InterfaceIT does not have this function. What you have to do is use FSUIPC to recognize the actions of the two switches that you want to be co-dependent. To do this you have to use a dummy offset in InterfaceIT for each switch so that its action will be recognized in FSUIPC. Dummy offsets start at 3360 and each offset can create nine buttons (1, 2, 3, 4, 5, 6, 7, 8, and 9). If you use Byte Setbit and Clearbit with the Bits being 0 through 9 for the switch action (Down/On and Up/Off) will be recognized in FSUIPC as a virtual joystick starting at Joy 72 button 0. Once the interdependent switches have been programmed in InterfaceIT and recognized in FSUPIC you can then edit the INI file to add modifiers for those two switches -- make switch A only operable if switch B is ON (or OFF) also can make switch A operable only if switches B and C are in certain positions.


This is the only way I know other than hard wiring of making switches dependent on each other. Hope this helps.


(Posted by Ron Rollo on 07-12-14)

Alan Norris found a theoretical way to use software logic to make these compound switches work correctly rather than using hardware logic. Here is what he sent via email:



Facilities are included to allow you to specify actions for one button which are dependent on the state of another button (or more likely, switch). This by using what I call ―Compound‖ button programming—though it could equally be ―Conditional‖ or ―Co-operative‖. Anyhow, I use the letter C in the definitions, as follows:


n=CP(+j2,b2)j,b, .... n=CU(+j2,b2)j,b, ... n=CP(–j2,b2)j,b, ... n=CU(–j2,b2)j,b, ...


Here the ‗C‘ denotes compound button checking, whilst P = pulse on pressing, U = pulse on releasing, as before. You can also use CR in place of CP for a repeating action—the repeats continue whilst all the conditions are true. There is no facility for the Hold action with the compound facilities.


Inside the parentheses are details of the secondary button, which must be in a certain condition for the current button to operate: 18


(+j2,b2) means that button b2 on joystick j2 must be pressed ("on") for the current button action (for j,b) to be obeyed.


So if you want switch A to be in the ON position before switch B can be operative then do the following:


In InterfaceIT:

For Switch A

Add an action and select Send to FSUIPC Down (On)

In the window that pops up use these:

Offset: 3360

Type: Byte

Operation: Set bit

Value: 0


Add another action and select Send to FSUIPC Up (Off)

In the window that pops up use these:

Offset: 3360

Type: Byte

Operation: Clear bit

Value: 0


For Switch B

Add an action and select Send to FSUIPC Down (On)

In the window that pops up use these:

Offset: 3360

Type: Byte

Operation: Set bit

Value: 1


Add another action and select Send to FSUIPC Up (Off)

In the window that pops up use these:

Offset: 3360

Type: Byte

Operation: Clear bit

Value: 1


Now open up FSUIPC and select the Buttons + Switches tab.

Press the Switch A UP, FSUIPC will recognize it as Joystick 72 Button 0

Check the Select for FS control box

In the drop down list select whatever that switch’s function is (e.g. Elevator Trim Switch Up)

Check the Control to repeat while held box

Put 0 in the Parameter box.

Press the Switch B switch DOWN, FSUIPC will recognize it as Joystick 72 Button 1

Check the Select for FS control box

In the drop down list select select whatever that switch’s function is (e.g. Elevator Trim Switch Down)

Check the Control to repeat while held box

Put 0 in the Parameter box.

Go to the FSUIPC INI file and find the buttons and switches section.


Switch A will show up as something like 67=J72,0 with some other information following that denotes it’s function to FSX and Switch B will be 68=J72,1


Then all you have to do is add a line at the end of the .ini file with the next number in the sequence such as:



This means that joystick 72 button 0 must be ON before joystick 72 button 1 will be functional. If you want joystick 72 button 0 to be OFF before joystick 72 button 1 will function then the line should read:




Thanks Alan for finding this valuable information.


This brings me to the next question: Of the fellas who have ordered the Pitch Trim Panel, which way would you prefer for me to wire the panel? I can make it so that it will utilize software logic like above or using hardware logic like described in post #13 in this thread. Once I get to that point of making wiring harnesses, I will ask each of you.


In the meantime, here is a quick update on the Pitch Trim Panels. The backers and hardware should be completed in less than two weeks. One of the switches had a very long back order but it came in a few weeks ago. I also finalized the rudder knob design last night and for what it is, you guys will be very happy with it. Here are a few photos of the production backer with one of Eric's prototype front plates:

Ron 1073


The is a close up of the special rudder knob and the pitch slider:

Ron 1074


Last but not least, this is a photo of the back side of the backer shower the hardware and the wiring:

Ron 1075


Speaking of wiring, as I was pointing out up a few threads ago, there are two ways to go about wiring the Pitch Trim Panel. I opted to go forward with the hardware logic route for now. I will wire up everyone's who has ordered the plug and play version so that it will be ready for hardware logic unless you say otherwise in this thread or via email. Worse case, it would only take about 30 minutes to convert to software logic.



The back side of the Pitch Trim Panels are complete!

Ron 1076


Here is a photo of the updated Rudder Trim Knob.  I used four pieces of .25" Acrylic to obtain the height of the knob. They turned out great:

Ron 1077


Eric is currently working on the front part of the panel and they should be ready in a few weeks!


(Posted by Alan Norris on 08-23-14)

IMO I would go the route of hardware logic as you don't have to mess around with programming as Ron mentioned above. Hardware logic is much simpler. In my case the panel I got from Vince did not have the double pole switch so I had to go the software route. Also my rudder trim is not self centering -- just a simple three position switch. No big deal as I will normally use the trim function on the yoke.


(Posted by Ron Rollo on 08-24-14)

Thanks guys, I think hardware logic is the way to go. As a matter of fact, the only thing that I am missing is the EICAS messages and all we would have to do is add another signal line to the double pole toggle to make that work. But like I said before, Jason would have to create that in Jet45 first.


Alan, in reference to your statement: "Also my rudder trim is not self centering -- just a simple three position switch. No big deal as I will normally use the trim function on the yoke."


Just so there is no confusion, the self centering rudder trim switch on the Pitch Trim Panel is different than the Roll Trim on the trim switch on the yokes. The four way trim switch on the yokes control pitch (elevator) and roll (aerilon). The two switches on the Pitch Trim panel are the secondary pitch trim (elevator) and the rudder trim, (yaw). But as you said, we would normally use the pitch trim on the yokes and rarely use any of the other trim switches.


(Posted by Mark Speechley on 10-24-14)

I am installing the Pitch trim Panel and looking at the wiring and the previous threads regarding the potential problems with the different commons. Do I just join all the black wires as one common and then install with the reds on the one FDS connector? Also you have hinted and then been asked by Alan regarding the procedure if you want to install in the FDS Relay card. Was that right ? If so could you give me/us an overview how this all fits together in your setup with the relay so that I can get on and install everything.


(Posted by Ron Rollo on 10-25-14)

As for this statement: "Now to be 100% correct the pitch trim switch on the yoke should not be able to control the aircraft if the PRI/SEC switch is in the SEC position but that would take a lot of wiring. The only way to do that is in software. Hope this helps."


What makes this pitch trim panel a little tough is that we are asking three different switches to do the same thing. I am talking about the pitch trim. We have one each on the yokes which is the PRI and the one on the panel which is the SEC. On top of that, when the two on the yokes are working the one on the panel is not working and vice versa.


I actually have my sim wired like this and yes, it does require extra wiring and headaches. But the good news is if you got a Pitch Trim panel from me it is wired and includes a wiring harness that has 90% of what you need to make it work. There should be either two red wires or two black wires coming from the toggle switch. These two wires will go to a double pole relay. You will also need to take the ground lines from the pitch trim switches on the yokes and send them to the relay. I need to get a wiring diagram posted up here which I will in the next 24 hours to help illustrate this.


(Posted by Mark Speechley on 10-26-14)

Have read your replies and wired the SYS board connector. Now have the 2 Black wires which you have enunciated Ron, from the Toggle switch that need to go to the FDS-SYS-R1X board.


Now for the important information that seems to be "secret squirrel" knowledge on the FDS Forum. Where is the information on how to wire this relay board ? A few people have asked and Pete Cos has sent them a file. Why sell a board with no instructions ?


Could you guys just give me the executive version please. I assume only the negative wire goes to a relay, but to NC, COM or NO? Thank you guys your help is immensely appreciated.


(Posted by Ron Rollo on 10-26-14)

Hey Mark, those two wires (either black or red) actually go to a double pole 12 volt relay, not the FDS relay. The reason we even need to have a relay is because we have to keep the grounds separated in each of the yokes. (In a minute this will all make sense)


Once you are ready to wire each of the yokes, check this thread out HERE


You will find that each yoke has eight inputs which works out great with the FDS cards. In other words, one FDS plug will handle each yoke, no problems right? Not so fast, because if you want to add the functionality of deselecting the pitch trim on both yokes at the same time, you have to temporarily cut the ground to both of them at the same time. This is where the double pole relay comes in. The double pole relay is able to cut the ground lines to both pitch trim switches at the same time and keep them separated from one another. Because remember, unless they are on the same 8 to 1 FDS plug, bad things will happen.


(Updated on 05-31-18)

The double pole relay gets power from your left ESS 12 volt BUS (or a source of 12 volt power) and is triggered by the pitch select toggle. Take a look at this wiring diagram for a good idea of how you will want to wire up your Pitch Trim System:

Pitch Trim Wiring Diagram

(Right click and select 'View Image")


NOTE: In order to make the Pitch Trim system function more like the real system, we had to increase the toggle switch from a two pole switch to a four pole switch.  We only needed one more pole but Honeywell does not make a three pole switch in this configuration.

In this wiring diagram above, pole two is the new addition.  These two new signal lines within pole two will go back to the FDS SYS card.  The three positions, (the center OFF position included) will be programed so that if the Autopilot is on and this switch is moved from any position to any of the other two, it will automatically disengage the AP.  This rule also applies to the trim switches on the yokes.

I have mine wired up and it works great. Like I was saying in an earlier post, there are a few issues that you will have with this hardware logic. First, it will not address the CAS messages 100%, but with that said, there are no CAS messages in Jet45 to be displayed at this point in time. The second issue is that the easiest way to break the ground line in the yokes is in the center area or hub of the yoke. Which means if you break the ground line for the trim switch, your going to be breaking the ground line for the Pitch select along with the roll trim as well. Take a look at this photo:

Ron 332


I thought about pulling my yokes apart and looking to find a way to isolate the pitch trim from the roll trim, but then I remembered that there is also the center push button that a HAS to be pushed to select any of the four trim positions on the switch. Long story short, I did not look into that any further, especially due to the fact that the trim select switch on the trim panel will always be in the PRI position anyway, it is only a "neat thing to have".


One other thought, if you want to make things easier on yourself, you can skip running the two red or black lines to the relay, etc.... All this would do is keep your PRI trim working all the time no matter what position the pitch select toggle is in. You would still be able to deselect the SEC trim switch though with the toggle. Just a thought for you.


I will also send you a drawing in your email so that it is easier to read. Anyone else that needs one just email me. I hope this helps.


(Posted by Mark Speechley on 10-27-14)

Thank you for the explanation. With your new diagram all fits nicely now. I initially got confused with the relay as opposed to the relay on the FDS Relay board. Back on track now.


Question on the toggle. Do I need the Single or double throw?


(Posted by Ron Rollo on 11-02-14)

DPDT. Make sure it is 12VDC and not 120VDC. If you have a radio shack the part number is 275-0218, but the last time I was there they had them on clearance. And what ever you get it has to be a double pole relay. The whole idea here is to keep the two ground wires from each of the yokes isolated from one another.


(Posted by Dave Simmons on 04-26-16)

Hi Ron, you have certainly done a lot of work. Would the switch at do for the pitch trim? It is much cheaper than the modified hat switch.


(Posted by Ron Rollo on 04-26-16)

Hey Dave, the switch you have pointed to does all the actions that the real switch does. It would be just a matter of designing it into the left horn of the pilot's side yoke. (Right horn for FO yoke) The other issue would be designing a circuit to integrate the center push to act as a safety for the four directions. It could either be within the yokes or wires running out of the yokes to take care of it elsewhere. Or you can skip that option as a few guys have done. The real switch which is very expensive, (up to $1,500 for one and we need two) has some built in hardware logic so that none of the four directions work unless you are pushing on the center button at the same time selecting a direction. Aviation safety feature.


CH yokes already have at least a four way if not a eight way hat switch. The center push is missing if I recall correctly.


A better switch for the application would be this one:


It is a tad over $7 and would be a better fit. It is an eight way switch but if you want four way, just ignore four of the pins. I just spent a few minutes testing this switch to see what pins are what. It also has the center push that you would need. I hope this helps!  Eric and Shane, this is the switch I was telling you about for the MFD JOYSTICK


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In order to make the Pitch Trim system function more like the real system, we had to increase the toggle switch from a two pole switch to a four pole switch.  We only needed one more pole but Honeywell does not make a three pole switch in this configuration.  I did some more reading up on the Pitch Trim System which is tightly integrated in with the Auto Pilot system and it did not take long to realize that what we have so far is just the tip of the iceberg when it comes to what is possible.  We may end up using that currently unused forth pole by the time we get the automated Auto Pilot System working!

For now, here is the updated Pitch Trim System wiring diagram.  This is a very functional design but still falls well short of the way the real system works.  As an example, while the AP is selected ON, we can still manually manipulate the pitch trim with the trim barrels on the yokes as long as we do not push the Arming Button in the center of the trim switches on the yokes.  This means I would have to rewire my yokes to make that Arming Button a separate switch from the trim barrel switch and then let software logic handle all the "If this is happening, then this will happen stuff".

You can right click on the image and select "View Image" to blow it up:

Pitch Trim System 1.2

In this wiring diagram above, pole two on the three position toggle switch is the new addition.  These two new signal lines within pole two will go back to the FDS SYS card.  The SEC and OFF positions will be programed so that if the Autopilot is on and this switch is moved to either SEC or OFF, it will automatically disengage the AP.  Remember, this switch is normally in the PRI position.  This rule also applies to the trim Arming Buttons on the yokes.


BomBardier Learjet 40/45 Pilot Training Guide - Autopilot Disengagement 2-13:

The autopilot is normally disengaged by depressing the AP button.

The autopilot can also be manually disengaged by the following actions:

1. Manually trimming the trim barrel and trim arming switch actuated

2. Activating the SEC TRIM switch

3. Selecting the pitch trim selector switch to OFF

4. Depressing the YD button (yaw damper disengagement)

5. Depressing the "Go Around" switch on the left thrust lever

6. Selecting either AHRS reversionary switch away from NORM

7. Depressing either control wheel master switch (MSW)


The bold areas above are the ways to disengage the AP via the trim system.  The main message here is that if you would like closer functionality to the real pitch trim system, your going to need to update to the Honeywell 4TL1-1A four pole Honeywell toggle, see photo below:

Three Position Toggle

You can find an example of a 4TL1-1A Honeywell switch at Galco  HERE