Sounds like this pretty prevalent. Having now had dinner (and Nic did a
superb chili - sorry for the diversion from topic), I've dug out the threads
of emails about it and have pasted them below.
Regards,
Jeremy
Europa XS Monowheel G-EZZA
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>--> AeroElectric-List message posted by: Sam Buchanan <sbuc@hiwaay.net>
>
>
>"Robert L. Nuckolls, III" wrote:
> >
> > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <bob.nuckolls@cox.net>
> >
> > >--> AeroElectric-List message posted by: Michel Therrien
> <mtherr@yahoo.com>
> > >
> > >
> > >Hello friends,
> > >
> > >For those of you using a Navaid Devices autopilot with
> > >a VFR panel (no VOR and only 1 VHF), do you (or should
> > >I) connect the optional diode to the PTT switch?
> > >
> > >I'll be using an Apollo SL-40 COM.
> >
> > I'm mystified as to what the Navaid has to do
> > with any wiring to the PTT switch. On who's
> > drawing is the diode mentioned and what notes
> > support the option decision?
> >
> > Bob . . .
>
>
>Bob, the diode is intended to momentarily disconnect the servo from the
>control head (I don't recall if it interrupts power or signal) when the
>PTT is activated. Apparently there have been some cases where RFI or
>something upset the servo during radio transmissions. The diode is shown
>on Navaid's installation diagrams.
>
>I included the diode in my Navaid installation even though I have no
>idea if it is necessary. The only downside of it is when I have allowed
>the plane to get significantly out of trim due to fuel imbalance; a
>slight roll will occur when the PTT is used.
Interesting! If you can't live with the stress, just shut it
off during stress . . . I'm not sure I'd take that approach
to solving an RF interference problem but I guess it would
work.
Bob . . .
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>--> AeroElectric-List message posted by: John Schroeder
><jschroeder@perigee.net>
>
>Sam -
>
>I believe that some of the problem here is that "PTT" has taken on too
>many meanings to be of use as an acronym - at least on this list. One
>is: Push-To-Talk. Another is: Push-To-Test, and yours is
>"Push-To-disconnecT. Maybe someone on the list can can come up with a
>more descriptive acronym for your situation.
>
>Mine is "APED": Auto Pilot Emergency Disconnect
Bizjets have buttons called "Wheel Master Disconnects"
that shut down all motor driven flight control surfaces
(a/p and trim servos) with the press of a single button.
There's another button on some aircraft called "Control
Wheel Steering" that disconnects autopilot steering for
duration of switch depression. Once released, the a/p
resumes it's last condition.
In this case, a "PTT" input to the autopilot is somewhat
analogous to "Control Wheel Steering" in that it temporarily
disables the autopilot . . . but for the wrong reasons.
Bob . . .
-----Original Message-----
From: forum-owner@europaclub.org.uk
Subject: Re: Navaid (Interference from Radio)
Mark,
Not a help but I have the same problem, I will keep a close eye on this
thread to see how you get on.
Good luck
Kev T
GOURO
-----Original Message-----
From: forum-owner@europaclub.org.uk
Subject: Navaid (Interference from Radio)
Dear All,
I have a Navaid Devices wing leveller fitted. When the PTT switch is pressed
to send on the radio, if the wing leveller is functioning, the aeroplane
does a violent turn to the left! The manual mentions the possibility of this
sort of interference and suggests proper shielding or the fitting of a cut
out switch that will disable the wing leveller when the PTT switch is
depressed.
My question is: Has anyone else had to do this retrospectively - and what is
the simplest solution please.
Mark
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