Positive Control - proper usage in the pattern

[Cruiser73]

Hello All,

I just purchased my first aircraft a real clean M20G.  I am doing some complex training with my instructor in my own plane(what a great feeling).  I have a little time in a M20C but that one didn't have the Positive control system.  The PC system seems helpful on the longer cross country but practicing in the pattern this seems to be a really pain.  When I search the forum for info about the PC system it seems to be talking about troubleshooting or disabling the system.  There was  even a photo of a rubber band on the button which would makes sense.  I found it irritating to hold the button as I started my base turn and all the way until touch down.   Especially because at the same time I am trying to find another finger to hit the PTT for radio calls. I know that you can just power past the system but it is really stiff and it feels like it is fight you.  As I was thinking about my flight today I wondered if I just need to hold it when I am making my turns.  If anyone has some practical tips on the proper usage in the traffic pattern with the PC system it would be helpful. 

 

Thanks

[Hank]

I just overpower the PC. It's a little stiff, but it reminds me to not overbank in the pattern, and to fly a little wider than I did in a C172 (about 2-3 blocks wider).

[takair]

After 24 years of flying with it, I find it automatic.  I just power through if I need the PTT.  If I’m doing training, I may remove the button to prevent cheating.

[Hector]

My 67C came with a switch in the panel to disable the PC system. The previous owner installed it and I’m grateful he did.


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[carusoam]

Welcome aboard c73.

1) original design is to hold the button down…

2) the next level, included an electric switch connected to a valve that dumps the vacuum…

3) band aids include the broccoli rubber band, or the 35mm film canister…

4) Plan B, is to over power the system manually…

5) Plan C, is to pop the valve button out of the yoke… many get lost or forgotten after a w

 

Being distracted in the traffic pattern, by a safety device… probably sets up its own unsafe condition…

There are many industrial 12v vacuum switches on the planet that would both improve the operation and the safety of the ancient system…

 

PP thoughts only… not a mechanic.

Best regards,

-a-

[McMooney]

you can pop the button up a bit to disable the pc.

I've just gotten used to flying with it on,  it's become muscle memory to push/release the pc button at this point

[DCarlton]

My '67F has a simple mechanical pneumatic cut out switch installed above the audio panel to deactivate the PC system.  It was installed by Brittain in Tulsa.  It doesn't have to be an electric switch.  I'll post a pic if I can find one.  I often disable the system in the pattern.  If it's really gusty I may leave it on. 

Edited November 22, 2021 by DCarlton

[Vance Harral]

2 hours ago, Cruiser73 said:

As I was thinking about my flight today I wondered if I just need to hold it when I am making my turns.

You already figured out the simplest answer.  Push the button when making a turn, release it when the turn is done.

[FastTex]

6 hours ago, Hank said:

I just overpower the PC. It's a little stiff, but it reminds me to not overbank in the pattern, and to fly a little wider than I did in a C172 (about 2-3 blocks wider).

I do the same. Just got used to it. At the next annual I will fix the button (the electric cylinder broke but I found the replacement)  but I might never use it. It flies great the way it is...

[Mooneymite]

Apparently the PC disconnect button on the left yoke horn isn't exactly the same on all installations.  Mine is quick/simple/easy to disengage by lifting the button.  Others, must rubber-band it down.

Regardless, the PC is just an autopilot.  It is appropriate for some phases of flight, but not all phases of flight.  I prefer to disengage my PC established in the VFR pattern, or runway in sight on an instrument approach.

[Hank]

Mostly, PC is a wing leveler. I turn off AccuTrak / AccuFlite as @Mooneymite described, but leave the basic PC function on.

[DCarlton]

Here's a pic of the panel mounted mechanical cut out switch ("Autopilot Master") I mentioned for the PC system.  It was installed by Brittain about 10-15 years ago during a PC system overhaul in Tulsa.  I use it often.  I'm glad I got a chance to meet Jerry and Kevin while Brittain was still active.  

[MBDiagMan]

I don’t have nearly as much experience with it as many here, but the only thing that bothers or effects me is PTT in the pattern.   I don’t have one of the switches that you can pull to diaable, so I have to hold the switch for maneuvering.  I have tried just muscling it, but I just feel like I will break something.  Having a quick and easy way to disable it would be the ideal solution.

[Bob R]

On 11/21/2021 at 7:30 PM, Cruiser73 said:

Hello All,

I just purchased my first aircraft a real clean M20G.  I am doing some complex training with my instructor in my own plane(what a great feeling).  I have a little time in a M20C but that one didn't have the Positive control system.  The PC system seems helpful on the longer cross country but practicing in the pattern this seems to be a really pain.  When I search the forum for info about the PC system it seems to be talking about troubleshooting or disabling the system.  There was  even a photo of a rubber band on the button which would makes sense.  I found it irritating to hold the button as I started my base turn and all the way until touch down.   Especially because at the same time I am trying to find another finger to hit the PTT for radio calls. I know that you can just power past the system but it is really stiff and it feels like it is fight you.  As I was thinking about my flight today I wondered if I just need to hold it when I am making my turns.  If anyone has some practical tips on the proper usage in the traffic pattern with the PC system it would be helpful. 

 

Thanks

I feel you. I do not like mine on in the pattern as well. Some have commented on using rubber bands, a 35mm film case, etc. I used to just pull the button out of the control wheel but that is hard on the o-ring but easily replaced. I am getting replacing my control wheels with J model wheels and new control wheel shafts. Goodbye AD. I was lucky and found one of the push/pull vacuum release valves. Keep looking I just got really lucky on ebay. While it might not be kosher, there is more than one way to skin a cat. There is lots of ways to dump the vacuum from the PC valve manually. I do have a line on the electric style. He is supposed to send it to me and if I can get it working, you are welcome to it. BTW, when I did not commercial in my E, I took the button out of the control wheel completely. The DPE did not mind at all nor did he care about right side brakes as someone else pointed out about their DPE. That whole PC system is not required for flight and can be removed to my knowledge.

[Cruiser73]

Thanks everyone for the input.  I flew several patterns today with just holding it through the turns and it does seem work ok but I think I in the future I will consider a disable switch. 

[Shadrach]

On 11/24/2021 at 8:17 PM, MBDiagMan said:

I don’t have nearly as much experience with it as many here, but the only thing that bothers or effects me is PTT in the pattern.   I don’t have one of the switches that you can pull to diaable, so I have to hold the switch for maneuvering.  I have tried just muscling it, but I just feel like I will break something.  Having a quick and easy way to disable it would be the ideal solution.

So you have a unique non Brittain switch? Do you have a pic?

[Shadrach]

4 minutes ago, Cruiser73 said:

Thanks everyone for the input.  I flew several patterns today with just holding it through the turns and it does seem work ok but I think I in the future I will consider a disable switch. 

Remember that the system takes a second to completely go off line when the button is pushed. Anticipating your turns and pushing the switch a second ahead of yoke inputs is good practice. I think that your newness to the airframe is making this a bigger deal than it is.  I’ve been flying it for nearly two decades and I hardly even think about it now.

[Shiny moose]

 Not that its legal but You only need a simple on off valve(humphrey makes such a valve)  to relieve the vacuum that goes to the yoke button, The hardest part to find will be a quality tee of the correct ID size for the small vacuum line, to small of an ID and you will restrict the vacuum enough that it will not relieve the PC.  3/16 OD tubing no ID demensions given. 

With a tight pc system and vaccum set to the higher side my mooney flew like a beechjet(no ailerons just spoilers) , at times 2 hands needed for turns more than just an adjustment( maybe I need to work out more) I personally like a lighter contol yoke or stick feel. I dont have a pc system any more, removing the servos made this mooney very light on the controls(GFC500 keeps her steady)

my .02

[Dave Morris]

With regard to using the PTT at the same time as you are pressing the PC button, this will teach you to make short, crisp radio calls. "Terrell Traffic, Mooney final 18 Terrell". 2.49 seconds.

[McMooney]

I feel, a properly working PC system is kinda like a cheat code, it just makes flying soooo easy.  

makes trivial approaches and ifr flying. 

once i upgrade to the trutrak( yeah i know ) or GFC 500, i feel i'm gonna miss it's firm handling.

I'd just fly the plane at some point you'll almost forget the system is working in the background.  

 

[DCarlton]

29 minutes ago, McMooney said:

I feel, a properly working PC system is kinda like a cheat code, it just makes flying soooo easy.  

makes trivial approaches and ifr flying. 

once i upgrade to the trutrak( yeah i know ) or GFC 500, i feel i'm gonna miss it's firm handling.

I'd just fly the plane at some point you'll almost forget the system is working in the background.  

 

Yep.  It's really nice when it's gusty on final.  Not sure how other autopilots respond in that situation; been too many years since I've flown anything different.  

[eman1200]

My 67C came with a switch in the panel to disable the PC system. The previous owner installed it and I’m grateful he did.


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Mine as well. Have never used it in the pattern a single time in over 4 years.

[MBDiagMan]

On 11/26/2021 at 5:09 PM, Shadrach said:

So you have a unique non Brittain switch? Do you have a pic?

I have no idea if it’s the original switch or a replacement.  I haven’t owned the plane since new.  When I bought it, Paul Maxwell thought that I could pull it out to disable, but we never were able to accomplish it.  I will be happy to post a picture if I can just remember your request when I’m at the hangar.

[Bob R]

19 hours ago, eman1200 said:

Mine as well. Have never used it in the pattern a single time in over 4 years.

Does it look like this? If so, it’s just a push/pull manual valve. I got lucky and found one on eBay about three weeks ago. It was being sold with some other Britain PC parts and I got to go to break it out.

[eman1200]

Does it look like this? If so, it’s just a push/pull manual valve. I got lucky and found one on eBay about three weeks ago. It was being sold with some other Britain PC parts and I got to go to break it out.

It does not look like that. Plane’s in for annual otherwise I’d snap a pic.