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GRT autopilot engage switch

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brian257

Well Known Member
I am currently installing autopilot servos on my GRT EFIS and I have not decided on the engage/disengage switches yet. They have the option for one pushbutton to engage/disengage both servos at the same time or separate buttons for pitch and roll. They also have the option for a separate disengage button which would normally be a button on the control stick.

I don't really have a place for the disengage button on the stick so that leaves me buttons on the panel. Having separate buttons for engaging pitch and roll sounds like it would be nice, but not really sure if I ever will engage roll only, certainly would never engage just pitch. The problem with two engage/disengage switches I am thinking is that then there are two buttons to press to disengage, which is less than convenient if you are disengaging on an IFR approach just after breaking through a low cloud layer. Picturing pressing one then the other and maybe in bumpy weather doing a double press one one and reengaging it accidently. The stand alone third button to disengage on the panel helps there, but do I really want three buttons cluttering the limited space I have? Would I be best off with just a single button press once to engage both servos and press again to disengage?

Can I get some thoughts from others on this.
 
I also considered that I might just be flipping the power switch to turn off power to the servos when disengaging instead of pressing the disengage switch. That seems safest, but I don't know if that then gives me alarms about autopilot not able to hold or loss of power while I am trying to concentrate on an approach or it it just shuts it off and does not start alarming.
 
One person's view ..

brian257 said:
I am currently installing autopilot servos on my GRT EFIS and I have not decided on the engage/disengage switches yet. They have the option for one pushbutton to engage/disengage both servos at the same time or separate buttons for pitch and roll. They also have the option for a separate disengage button which would normally be a button on the control stick.

I don't really have a place for the disengage button on the stick so that leaves me buttons on the panel. Having separate buttons for engaging pitch and roll sounds like it would be nice, but not really sure if I ever will engage roll only, certainly would never engage just pitch. The problem with two engage/disengage switches I am thinking is that then there are two buttons to press to disengage, which is less than convenient if you are disengaging on an IFR approach just after breaking through a low cloud layer. Picturing pressing one then the other and maybe in bumpy weather doing a double press one one and reengaging it accidently. The stand alone third button to disengage on the panel helps there, but do I really want three buttons cluttering the limited space I have? Would I be best off with just a single button press once to engage both servos and press again to disengage?

Can I get some thoughts from others on this.
Click to expand...

Suggestions:
1. Use a power switch as suggested to supply power to servos and to serve as the final override.
2. Use one button for "Engage"disengage" of BOTH servos simultaneously.

This is what I have on my RV6 (panel button --RED) and on my RV8 (stick grip - INFINITY grip, right under my thumb).

I have not had an occasion where I wished that I had had the two buttons, one for each servo and thus the ability to have "Control Wheel Steering".

James
 
Having 2 buttons for 'engage' can be useful for trouble shooting, but if you use the autopilot for ifr approaches then I think you want one, very accessible, button to disengage. I have a Trio Pro and can disengage with one stick button, or two autopilot panel buttons, or one power switch right over the EFIS, or one CB directly in front of me. Autopilots are great when they work, but if they fail you want them disconnected right now.
 
Thanks James. And good to talk to you again. We met at Trippletree a few years ago and again at Dan Heath's hanger. I have the Yellow Mustang 2. You talked me into getting the bigger GRT EFIS instead of waiting for the Mini to come out and I am happy you did. Adding an SL30, Garmin 155 GPS, and the servos now.
 
brian257 said:
I am currently installing autopilot servos on my GRT EFIS and I have not decided on the engage/disengage switches yet. They have the option for one pushbutton to engage/disengage both servos at the same time or separate buttons for pitch and roll. They also have the option for a separate disengage button which would normally be a button on the control stick.

I don't really have a place for the disengage button on the stick so that leaves me buttons on the panel. Having separate buttons for engaging pitch and roll sounds like it would be nice, but not really sure if I ever will engage roll only, certainly would never engage just pitch. The problem with two engage/disengage switches I am thinking is that then there are two buttons to press to disengage, which is less than convenient if you are disengaging on an IFR approach just after breaking through a low cloud layer. Picturing pressing one then the other and maybe in bumpy weather doing a double press one one and reengaging it accidently. The stand alone third button to disengage on the panel helps there, but do I really want three buttons cluttering the limited space I have? Would I be best off with just a single button press once to engage both servos and press again to disengage?

Can I get some thoughts from others on this.
Click to expand...

Problem with the disengage button on the control column is that it is not instant, it takes 2 seconds to work, way too long when things go wrong. The engage/ disengage button on the panel is immediate and works way better.

Power switch and engage/ disengage button close by on the panel works best
 
I have a power switch and separate buttons on the panel. During flight I can disengage each servo separately to check the trim. It's also nice to turn one or the other off to deviate for clouds or anything else. To quickly disengage both just flip the power switch.
 
Huh??

petersb said:
Problem with the disengage button on the control column is that it is not instant, it takes 2 seconds to work, way too long when things go wrong. The engage/ disengage button on the panel is immediate and works way better.

Power switch and engage/ disengage button close by on the panel works best
Click to expand...

Huh???
How is that so????

The EXACT same wires are connected to ground in my case, whether the "button" is on the panel (RV6) or on the stick grip (RV8).

Help us understand how this is so in your case.

Thanks,


James
 
seperate buttons

brian257 said:
...
Having separate buttons for engaging pitch and roll sounds like it would be nice, but not really sure if I ever will engage roll only, certainly would never engage just pitch.
...
Click to expand...

In my experience, the pitch servo can be easily overwhelmed in turbulence. I often disengage Altitude Hold under those conditions but keep the roll (steering) engaged.
 
jclark said:
Huh???
How is that so????

The EXACT same wires are connected to ground in my case, whether the "button" is on the panel (RV6) or on the stick grip (RV8).

Help us understand how this is so in your case.

Thanks,


James
Click to expand...


Sure, control stick disengage button is connected to pin 7 on roll servo, engage/disengage button is connected to pin 5 on the roll/pitch servos as per page 16 of the installation manual


Peter
 
I have the split pitch and roll engage on the panel and use them as already stated by others. Because of the 2 second delay, the stick disengage is useless. I never use it.
 
rzbill said:
Because of the 2 second delay, the stick disengage is useless. I never use it.
Click to expand...

This is a photo of one of my GRT engage/disengage switches.

22674456517_3a5db779f7_b.jpg


It's the red one below the mixure. Very convenient when cruising along handflying the ship.

I also have one on my stick grip where the flap toggle is usually located. I had my grip made with just the switches I needed and I didn't like the flaps on the stick.

22471796483_a3e332a7c2_o.jpg

As you can see the flaps are located on the rear of my throttle quadrant side.

Back to the opening post question.

I had mine on the quadrant until I put in the Infinity grip. I have a COM swap and A/P eng/diseng. switch on the stick. For me personally having a separate switch for both axis's wasn't even a consideration. I do however like having the switch on the stick. As for the 2 second delay on the switch I don't have that. Both of my switches are instantaneous.
 
Thanks for the replies.

I am now leaning towards putting both buttons on the panel, but just flipping the power switch to turn it off.

I did look in the manual and it seems to indicate that pushing the roll disengage when you have both buttons will actually disengage both, but pushing the pitch will only disengage pitch. This seems like a good solution since I might want to disengage pitch to check trim. Can anyone with two buttons confirm that pressing just the roll will disengage both.

Also, can anyone tell me what happens when you shut the autopilot power. Does that give alarms that need to be acknowledged and would be distracting as I am just breaking out of the soup on an approach?
 
Got it ...

petersb said:
Sure, control stick disengage button is connected to pin 7 on roll servo, engage/disengage button is connected to pin 5 on the roll/pitch servos as per page 16 of the installation manual


Peter
Click to expand...

Thanks,

I now see my "disconnect" from your comments.

I missed in your original post that you were talking about the "engage/disengage" **AND** the "engage" (which I will refer to as control wheel steering.

I wired ONLY the combined "engage/disengage" for both pitch and roll in the two different cases I mentioned. One on the panel and one on the stick grip.

For me this has been adequate in both cases.

James
 
Here is an image of my switches located on the instrument panel just above the throttles. And engage/disengage push button, Servo Power which powers both pitch and roll, as well as serial select between my mini and HXr. This has served me well for many years.

switches.jpg
 
brian257 said:
Thanks for the replies.

....I did look in the manual and it seems to indicate that pushing the roll disengage when you have both buttons will actually disengage both, but pushing the pitch will only disengage pitch. This seems like a good solution since I might want to disengage pitch to check trim. Can anyone with two buttons confirm that pressing just the roll will disengage both...
Click to expand...


Brian,

There is no need to disengage the pitch mode just to check the trim. The pitch trim torque indication will tell you if the elevator is out of trim. Excerpt from the GRT AP installation manual follows:

Pitch trim advisories appear above the altimeter tape only when action is required. The higher the number, the higher the torque imbalance. The arrow points in the direction of the required trim adjustment. Green arrows represent a mild trim adjustment, while yellow/red arrows represent large trim adjustments that can break a shear pin or damage the servo if not remedied immediately.
 
Last edited:
N459RC said:
I have a power switch and separate buttons on the panel. During flight I can disengage each servo separately to check the trim. It's also nice to turn one or the other off to deviate for clouds or anything else. To quickly disengage both just flip the power switch.
Click to expand...

I wired the same setup and it works for me. Yes, I have flown with only one servo engaged, especially when you want to climb out on course.

Jim
RV Niner a
 
jclark said:
Thanks,

I now see my "disconnect" from your comments.

I missed in your original post that you were talking about the "engage/disengage" **AND** the "engage" (which I will refer to as control wheel steering.

I wired ONLY the combined "engage/disengage" for both pitch and roll in the two different cases I mentioned. One on the panel and one on the stick grip.

For me this has been adequate in both cases.

James
Click to expand...

Thinking of copying you as this will give an immediate disconnect

Peter
 
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