Today's Message Index:
----------------------
1. 12:59 AM - Re: Rotax 914 (Duncan & Ami McFadyean)
2. 01:21 AM - Re: Rotax 914 (Craig Payne)
3. 08:22 AM - Re: Rotax 914 (Noel Loveys)
4. 09:07 AM - Re: Rotax 914 (Noel Loveys)
5. 01:09 PM - Re: carb ice revisited (avid2008)
6. 02:14 PM - Re: Rotax 914 (Duncan & Ami McFadyean)
7. 02:43 PM - Re: Rotax 914 (Craig Payne)
8. 03:26 PM - Re: Rotax 914 (Noel Loveys)
9. 03:41 PM - Re: Rotax 914 (Noel Loveys)
10. 05:48 PM - Re: carb ice revisited (Roger Lee)
Message 1
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RE: RotaxEngines-List: Rotax 914Yet the Rotax manual (later versions)
show grounding of the shield at both ends, with a statement to the
effect that their EMI compliance is not maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys
To: rotaxengines-list@matronics.com
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering
with your radios.. When you ground these leads they turn off (short
out) the magnetos so the engine will stop. Generally, coax should only
be grounded at one end, the engine end. Grounding at both ends makes the
coax an inductive emitter if the signal is high enough on the centre
lead.
When you wire your plane be sure to have a good hefty braid (ground)
going from the engine block across the lord mounts to a sturdy place on
the frame. Doing that will lower the possibility of radio interference
and it will ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of
Fergus Kyle
Sent: Thursday, September 18, 2008 11:18 AM
To: ROTAXnet
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to
the ignition switches, ensuring that the coax braid is exclusively
connected to nearby engine ground at one end and one pole of each switch
at the other.
The switches are enclosed in small alum boxes attached to the panel
for interference protection.
I see, by Installation manual, page 75 [electric circuit,
d/1996 05 10] that there seems to be an electrical ground connection to
the switch frame and thus to the metal panel on which it is fixed. If
that is so, then the engine frame ground extends into the cockpit via
the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
Message 2
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Does it actually show the shield grounded at the switch or is the shield
just connected to a terminal on the switch? The common
off-left-right-both-start switch from Aircraft Spruce has terminals on it
labeled "GRD" which the shields connect to. But they don't actually connect
to the metal frame of the switch case. They are just the terminals that the
switch connects the P leads to when killing that half of the ignition. I've
attached a snippet from diagram Z-27 in the AeroElectric update on page 30
at the link below. The table shows what actually happens inside the switch.
https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 1:56 AM
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at both
ends, with a statement to the effect that their EMI compliance is not
maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering with
your radios.. When you ground these leads they turn off (short out) the
magnetos so the engine will stop. Generally, coax should only be grounded
at one end, the engine end. Grounding at both ends makes the coax an
inductive emitter if the signal is high enough on the centre lead.
When you wire your plane be sure to have a good hefty braid (ground) going
from the engine block across the lord mounts to a sturdy place on the frame.
Doing that will lower the possibility of radio interference and it will
ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Thursday, September 18, 2008 11:18 AM
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to the
ignition switches, ensuring that the coax braid is exclusively connected to
nearby engine ground at one end and one pole of each switch at the other.
The switches are enclosed in small alum boxes attached to the panel for
interference protection.
I see, by Installation manual, page 75 [electric circuit, d/1996 05
10] that there seems to be an electrical ground connection to the switch
frame and thus to the metal panel on which it is fixed. If that is so, then
the engine frame ground extends into the cockpit via the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
Message 3
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That is probably true but coax is an unbalanced feed cable grounding at both
ends will enable the whole wire to become a capacitive radiator.
Capacitors as you know pass AC and block DC the problem is the current
feeding the P-Leads is AC. Grounding at the engine end only allows any
induced AC into the shield to be grounded rather than swing back and forth
in the shield. The only exception to the rule is for antennae. The feed
end (radio) of the coax is grounded to the case of the radio and the far end
of the coax should have an good ground to form a ground plane for the
antenna radiator. In that case the ground part of the antenna end should be
very clean. A lot of problems with com radios rise from corroded ground
terminals at the antenna end. That is one of the first things I will check
when there is a radio problem in an airplane. A bad ground in that location
can cause other physical problems within the radio itself. The same thing
is true for other avionics. Good clean grounds and shielded cables grounded
at the source end only.
Rotax may have specified double grounding because of bad grounds across the
engine mounts. That could have caused the P-Lead not to work properly. It
is my personal experience as a Canadian AME intern (Aircraft Maintenance
Engineer) with specialty training in avionics and an Amateur Radio operator
with an advanced licence for over twenty years, that 90 % of electrical and
avionics problems are due to bad grounding. The general rule of thumb is to
ground closest to the source. This grounding at one end only should
continue throughout the full avionics suite. Perhaps if there is someone
from the Rotax design team on line they could let us know why they spec
double grounding of coaxial cable.
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 5:26 AM
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at both
ends, with a statement to the effect that their EMI compliance is not
maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering with
your radios.. When you ground these leads they turn off (short out) the
magnetos so the engine will stop. Generally, coax should only be grounded
at one end, the engine end. Grounding at both ends makes the coax an
inductive emitter if the signal is high enough on the centre lead.
When you wire your plane be sure to have a good hefty braid (ground) going
from the engine block across the lord mounts to a sturdy place on the frame.
Doing that will lower the possibility of radio interference and it will
ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Thursday, September 18, 2008 11:18 AM
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to the
ignition switches, ensuring that the coax braid is exclusively connected to
nearby engine ground at one end and one pole of each switch at the other.
The switches are enclosed in small alum boxes attached to the panel for
interference protection.
I see, by Installation manual, page 75 [electric circuit, d/1996 05
10] that there seems to be an electrical ground connection to the switch
frame and thus to the metal panel on which it is fixed. If that is so, then
the engine frame ground extends into the cockpit via the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
Message 4
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You're spot on. The shield is only grounded at the switch end when the mag
is turned off. Fig Z-11
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig
Payne
Sent: Friday, September 19, 2008 5:51 AM
Subject: RE: RotaxEngines-List: Rotax 914
Does it actually show the shield grounded at the switch or is the shield
just connected to a terminal on the switch? The common
off-left-right-both-start switch from Aircraft Spruce has terminals on it
labeled "GRD" which the shields connect to. But they don't actually connect
to the metal frame of the switch case. They are just the terminals that the
switch connects the P leads to when killing that half of the ignition. I've
attached a snippet from diagram Z-27 in the AeroElectric update on page 30
at the link below. The table shows what actually happens inside the switch.
https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 1:56 AM
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at both
ends, with a statement to the effect that their EMI compliance is not
maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering with
your radios.. When you ground these leads they turn off (short out) the
magnetos so the engine will stop. Generally, coax should only be grounded
at one end, the engine end. Grounding at both ends makes the coax an
inductive emitter if the signal is high enough on the centre lead.
When you wire your plane be sure to have a good hefty braid (ground) going
from the engine block across the lord mounts to a sturdy place on the frame.
Doing that will lower the possibility of radio interference and it will
ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Thursday, September 18, 2008 11:18 AM
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to the
ignition switches, ensuring that the coax braid is exclusively connected to
nearby engine ground at one end and one pole of each switch at the other.
The switches are enclosed in small alum boxes attached to the panel for
interference protection.
I see, by Installation manual, page 75 [electric circuit, d/1996 05
10] that there seems to be an electrical ground connection to the switch
frame and thus to the metal panel on which it is fixed. If that is so, then
the engine frame ground extends into the cockpit via the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com
http://www.matronics.com/contribution
Message 5
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| Subject: | Re: carb ice revisited |
Roger, I have always been told that R912 is pretty much ice-proof. Last winter
I discovered the contrary although it must be said in all fairness that conditions
were prone to icing.
I purchaised a Rotax 912 powered Avid Flyer and was ferrying it accross Europe
in the company of the previous owner. It was around 0C and very humid; the guy
was running it at 4500rpm. After about 20min of flight I noticed that revs
were around 4200 and quite uneven; I pushed in some more throttle with no effect,
then after some 30-60secs suddenly revs came up to 5000. We kept it at 4800-5000
for the rest of the day( 6hrs/2 landings) without any further problem.
The next day the valley where we stopped for the night was filled with stratus
and occasionally there were some drops of rain. Hardly a VFR type of weather but
we decided to try to take off. While warming up the engine I noticed that
it was running VERY rough - I couldn't check above 3500rpm as the brakes were
not strong enough to hold the plane, but anything below 3500rpm was very uneven.
Not being certain if there is everything OK with the engine and having marginal
weather we decided to postpone the takeoff.
Next day I called a local FBO mechanic (I had to go back home by train) and asked
him to check the engine. The weather was fine and he didn't have any problem.
I feel very strongly we must have experienced carb icing.
I did 70hrs with this plane since that day and I must say that on a couple of occasions
I had a suspicion of icing (not as apparent as described above, but a
slight irregularity below 4000rpm) in humid conditions. Adding power has always
improved the situation.
I must say that the Avid Flyer has huge air intakes on both sides of the prop,
so presumably there is no wam air stagnating under the cowl (as it is frequently
the case of modern planes with sleek cowlings). Warmer air in the carb area
can probably help, although it is not a 100% solution (FAA wants to see, if memory
serves me well, at least 70F air temp increase to be considered as an efficient
carb heat).
Martin
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 5127#205127
Message 6
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RE: RotaxEngines-List: Rotax 914Except that the Rotax manual shows a
different set-up, with each end of the screen grounded, the switch body
grounded and the centre-conductor of the shielded wire switched to a
separate ground when the kill-switch is closed. The descriptions in the
text of the manual confirm the indications of the diagram.
Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"!
Duncan McF.
----- Original Message -----
From: Noel Loveys
To: rotaxengines-list@matronics.com
Sent: Friday, September 19, 2008 4:29 PM
Subject: RE: RotaxEngines-List: Rotax 914
You're spot on. The shield is only grounded at the switch end when
the mag is turned off. Fig Z-11
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig
Payne
Sent: Friday, September 19, 2008 5:51 AM
To: rotaxengines-list@matronics.com
Subject: RE: RotaxEngines-List: Rotax 914
Does it actually show the shield grounded at the switch or is the
shield just connected to a terminal on the switch? The common
off-left-right-both-start switch from Aircraft Spruce has terminals on
it labeled "GRD" which the shields connect to. But they don't actually
connect to the metal frame of the switch case. They are just the
terminals that the switch connects the P leads to when killing that half
of the ignition. I've attached a snippet from diagram Z-27 in the
AeroElectric update on page 30 at the link below. The table shows what
actually happens inside the switch.
https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of
Duncan & Ami McFadyean
Sent: Friday, September 19, 2008 1:56 AM
To: rotaxengines-list@matronics.com
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at
both ends, with a statement to the effect that their EMI compliance is
not maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys
To: rotaxengines-list@matronics.com
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering
with your radios.. When you ground these leads they turn off (short
out) the magnetos so the engine will stop. Generally, coax should only
be grounded at one end, the engine end. Grounding at both ends makes the
coax an inductive emitter if the signal is high enough on the centre
lead.
When you wire your plane be sure to have a good hefty braid (ground)
going from the engine block across the lord mounts to a sturdy place on
the frame. Doing that will lower the possibility of radio interference
and it will ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of
Fergus Kyle
Sent: Thursday, September 18, 2008 11:18 AM
To: ROTAXnet
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In
the process, I wired the dynamo module wires to coaxial cable which runs
to the ignition switches, ensuring that the coax braid is exclusively
connected to nearby engine ground at one end and one pole of each switch
at the other.
The switches are enclosed in small alum boxes attached to the panel
for interference protection.
I see, by Installation manual, page 75 [electric circuit,
d/1996 05 10] that there seems to be an electrical ground connection to
the switch frame and thus to the metal panel on which it is fixed. If
that is so, then the engine frame ground extends into the cockpit via
the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.
matronics.com/Navigator?RotaxEngines-Listhref="http://forums.matronics.
com">http://forums.matronics.comhref="http://www.matronics.com/contribu
tion">http://www.matronics.com/c
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com http://www.matronics.com/contribution
Message 7
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Do you mean figures 67 and 73 from the installation manual (or the
equivalent)? I've attached a copy of each. They certainly do appear to be
grounding both ends of the shield in figure 73.
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 3:11 PM
Subject: Re: RotaxEngines-List: Rotax 914
Except that the Rotax manual shows a different set-up, with each end of the
screen grounded, the switch body grounded and the centre-conductor of the
shielded wire switched to a separate ground when the kill-switch is closed.
The descriptions in the text of the manual confirm the indications of the
diagram.
Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"!
Duncan McF.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:29 PM
Subject: RE: RotaxEngines-List: Rotax 914
You're spot on. The shield is only grounded at the switch end when the mag
is turned off. Fig Z-11
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig
Payne
Sent: Friday, September 19, 2008 5:51 AM
Subject: RE: RotaxEngines-List: Rotax 914
Does it actually show the shield grounded at the switch or is the shield
just connected to a terminal on the switch? The common
off-left-right-both-start switch from Aircraft Spruce has terminals on it
labeled "GRD" which the shields connect to. But they don't actually connect
to the metal frame of the switch case. They are just the terminals that the
switch connects the P leads to when killing that half of the ignition. I've
attached a snippet from diagram Z-27 in the AeroElectric update on page 30
at the link below. The table shows what actually happens inside the switch.
https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 1:56 AM
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at both
ends, with a statement to the effect that their EMI compliance is not
maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering with
your radios.. When you ground these leads they turn off (short out) the
magnetos so the engine will stop. Generally, coax should only be grounded
at one end, the engine end. Grounding at both ends makes the coax an
inductive emitter if the signal is high enough on the centre lead.
When you wire your plane be sure to have a good hefty braid (ground) going
from the engine block across the lord mounts to a sturdy place on the frame.
Doing that will lower the possibility of radio interference and it will
ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Thursday, September 18, 2008 11:18 AM
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to the
ignition switches, ensuring that the coax braid is exclusively connected to
nearby engine ground at one end and one pole of each switch at the other.
The switches are enclosed in small alum boxes attached to the panel for
interference protection.
I see, by Installation manual, page 75 [electric circuit, d/1996 05
10] that there seems to be an electrical ground connection to the switch
frame and thus to the metal panel on which it is fixed. If that is so, then
the engine frame ground extends into the cockpit via the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com
http://www.matronics.com/contribution
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
Message 8
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We don't shoot messengers around here except with shots of Scotch, Rum, Corn
or Brandy! Double barrels are encouraged by most victims! I would be
interested in why Rotax specifies both ends of the shield to be grounded
though. Anyone have any ideas?
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 6:41 PM
Subject: Re: RotaxEngines-List: Rotax 914
Except that the Rotax manual shows a different set-up, with each end of the
screen grounded, the switch body grounded and the centre-conductor of the
shielded wire switched to a separate ground when the kill-switch is closed.
The descriptions in the text of the manual confirm the indications of the
diagram.
Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"!
Duncan McF.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:29 PM
Subject: RE: RotaxEngines-List: Rotax 914
You're spot on. The shield is only grounded at the switch end when the mag
is turned off. Fig Z-11
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig
Payne
Sent: Friday, September 19, 2008 5:51 AM
Subject: RE: RotaxEngines-List: Rotax 914
Does it actually show the shield grounded at the switch or is the shield
just connected to a terminal on the switch? The common
off-left-right-both-start switch from Aircraft Spruce has terminals on it
labeled "GRD" which the shields connect to. But they don't actually connect
to the metal frame of the switch case. They are just the terminals that the
switch connects the P leads to when killing that half of the ignition. I've
attached a snippet from diagram Z-27 in the AeroElectric update on page 30
at the link below. The table shows what actually happens inside the switch.
https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 1:56 AM
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at both
ends, with a statement to the effect that their EMI compliance is not
maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering with
your radios.. When you ground these leads they turn off (short out) the
magnetos so the engine will stop. Generally, coax should only be grounded
at one end, the engine end. Grounding at both ends makes the coax an
inductive emitter if the signal is high enough on the centre lead.
When you wire your plane be sure to have a good hefty braid (ground) going
from the engine block across the lord mounts to a sturdy place on the frame.
Doing that will lower the possibility of radio interference and it will
ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Thursday, September 18, 2008 11:18 AM
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to the
ignition switches, ensuring that the coax braid is exclusively connected to
nearby engine ground at one end and one pole of each switch at the other.
The switches are enclosed in small alum boxes attached to the panel for
interference protection.
I see, by Installation manual, page 75 [electric circuit, d/1996 05
10] that there seems to be an electrical ground connection to the switch
frame and thus to the metal panel on which it is fixed. If that is so, then
the engine frame ground extends into the cockpit via the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com
http://www.matronics.com/contribution
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nics.com/Navigator?RotaxEngines-List
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Message 9
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It may be that with the conductor only grounded at one end the mag(s) may be
cut off because of EMI within the cable... that's the way I read it.
However grounding at both ends will no doubt cause a great increase in RFI.
In such a case I'd recommend a double shielded wire with the outside shield
grounded at the engine end only. Sounds like a catch 22. Either the engine
may shut itself down or you won't be able to receive any thing on your
radios...Com or nav.
One thing is for sure I'm going to get the chance to find out for sure in
the very near future as I'm installing a 912 in my plane.
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig
Payne
Sent: Friday, September 19, 2008 7:13 PM
Subject: RE: RotaxEngines-List: Rotax 914
Do you mean figures 67 and 73 from the installation manual (or the
equivalent)? I've attached a copy of each. They certainly do appear to be
grounding both ends of the shield in figure 73.
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 3:11 PM
Subject: Re: RotaxEngines-List: Rotax 914
Except that the Rotax manual shows a different set-up, with each end of the
screen grounded, the switch body grounded and the centre-conductor of the
shielded wire switched to a separate ground when the kill-switch is closed.
The descriptions in the text of the manual confirm the indications of the
diagram.
Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"!
Duncan McF.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:29 PM
Subject: RE: RotaxEngines-List: Rotax 914
You're spot on. The shield is only grounded at the switch end when the mag
is turned off. Fig Z-11
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig
Payne
Sent: Friday, September 19, 2008 5:51 AM
Subject: RE: RotaxEngines-List: Rotax 914
Does it actually show the shield grounded at the switch or is the shield
just connected to a terminal on the switch? The common
off-left-right-both-start switch from Aircraft Spruce has terminals on it
labeled "GRD" which the shields connect to. But they don't actually connect
to the metal frame of the switch case. They are just the terminals that the
switch connects the P leads to when killing that half of the ignition. I've
attached a snippet from diagram Z-27 in the AeroElectric update on page 30
at the link below. The table shows what actually happens inside the switch.
https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf
-- Craig
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan &
Ami McFadyean
Sent: Friday, September 19, 2008 1:56 AM
Subject: Re: RotaxEngines-List: Rotax 914
Yet the Rotax manual (later versions) show grounding of the shield at both
ends, with a statement to the effect that their EMI compliance is not
maintained otherwise.
Duncan Mcf.
----- Original Message -----
From: Noel Loveys <mailto:noelloveys@yahoo.ca>
Sent: Friday, September 19, 2008 4:20 AM
Subject: RE: RotaxEngines-List: Rotax 914
The ground on the shield is to prevent the P-leads from interfering with
your radios.. When you ground these leads they turn off (short out) the
magnetos so the engine will stop. Generally, coax should only be grounded
at one end, the engine end. Grounding at both ends makes the coax an
inductive emitter if the signal is high enough on the centre lead.
When you wire your plane be sure to have a good hefty braid (ground) going
from the engine block across the lord mounts to a sturdy place on the frame.
Doing that will lower the possibility of radio interference and it will
ensure you get lots of cranking amps to your starter too.
Noel
_____________________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Thursday, September 18, 2008 11:18 AM
Subject: RotaxEngines-List: Rotax 914
Hello,
I am assembling the wiring for the above model engine. In the
process, I wired the dynamo module wires to coaxial cable which runs to the
ignition switches, ensuring that the coax braid is exclusively connected to
nearby engine ground at one end and one pole of each switch at the other.
The switches are enclosed in small alum boxes attached to the panel for
interference protection.
I see, by Installation manual, page 75 [electric circuit, d/1996 05
10] that there seems to be an electrical ground connection to the switch
frame and thus to the metal panel on which it is fixed. If that is so, then
the engine frame ground extends into the cockpit via the coax.
Is this the intent?
What is its purpose, please?
Ferg
Europa A064
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com
http://www.matronics.com/contribution
href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro
nics.com/Navigator?RotaxEngines-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com
http://www.matronics.com/contribution
Message 10
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| Subject: | Re: carb ice revisited |
Hi Guys,
Please don't take my next comment as being a smart ass, but how do you guys know
if it was really icing without any confirmation and have you ruled out all other
possibilities? Without confirmation it still is speculation. These are not
standard carbs like the ones we were raised with during our life, but quite
different. These are variable venturi carbs. That in itself makes them less prone
to standard icing effects.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Service Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 5184#205184
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