Today's Message Index:
----------------------
1. 08:39 AM - Re: Request for some direction and advise (Robert L. Nuckolls, III)
2. 10:10 AM - Re: Request for some direction and advise (Robert L. Nuckolls, III)
3. 03:19 PM - Re: Request for some direction and advise (Robert L. Nuckolls, III)
4. 03:50 PM - Opportunity alert (Robert L. Nuckolls, III)
5. 04:31 PM - Hydraulic Pump Start-Up Amperage (Dennis Johnson)
6. 05:39 PM - =?utf-8?Q?_Hydraulic_Pump_Start-Up_Amperage? ()
7. 06:34 PM - Re: Hydraulic Pump Start-Up Amperage (Robert L. Nuckolls, III)
8. 08:21 PM - Re: Re: Request for some direction and advise (Bill Bradburry)
Message 1
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Subject: | Re: Request for some direction and advise |
At 03:17 PM 8/29/2015, you wrote:
Bob,
I apologize for writing you directly but I am at my wits end with this problem.
Not a problem except that we should do this
on the List . . . there are individuals who
are able and willing to contribute to the
study/solution, many more who would benefit
from reading the exchanges . . ..
First let me tell you that I have a GNS430W and a TruTrack Digiflight
II VSVG autopilot along with the Dynon 10A and Dynon HS34 module to
connect the Dynon to the GNS430W.
I have always had a problem with the radio developing a lot of static
on certain frequencies to the extent that I could not make out what
was being said. Not always, but mostly I would get this very loud
ShShShShSh! On frequencies like 121.1 which is approach for the Orlando area.
Since I have now moved to the Dallas area, the problem has changed to
a much worse condition. Now when I key the mike, I sometimes get the
autopilot kicking off, sometimes the radio kicks off, and the last
couple of flights, the electrically dependent engine will all but die
while I have the mike key depressed. I am not finished with living,
so I have to find and fix this before I fly again.
This sounds like two separate problems. What kind of airplane
and where is the comm antenna installed?
I have no real knowledge of electrical things, but I used to think
that I could follow directions and connect wires. I am beginning to
think I may have been wrong about that!
I can not think of anything that would cause this phenomenon when the
mike is keyed. Hopefully you can come up with some direction that I
can follow to discover a cause. I have come to think that somehow I
must be getting a voltage on this ground line that is then feeding
back to all the equipment in the plane. The thing is, I really don't
have any clue about how I would go about testing for such a thing
even if that turns out to be the problem.
Let's get all the data before we begin picking
at straws . . .
What I hope is that something in this problem will strike a pattern
to you that will allow you to give me a direction to look for the
problem. If it does, I would need some pretty explicit directions as
to what and how to test whatever you think would make sense to test.
I know this is rambling and non-specific, but if you should need any
more info, I will be happy to try and provide it.
Thanks for all the help you have given all of us in the past and
hopefully you can come up with a little assistance for me here.
Not a problem, its what we do here. But at the
same time, know that diagnostics by e-mail are
fraught with risk for lack of understanding
and forcing unnecessary delays. Are there
no builders and/or radio cognizant acquaintances
local to you that could participate in this
activity? I suspect that the root cause is
simple . . . it usually is.
Have you physically checked the antenna coax
from the back of the radio to the antenna? Unhook
the coax, tug on the connectors at both ends.
See if they can be 'twisted' on the wire. Their
attachment should be quite robust 5=10 pounds
of pull or twisting with the fingers should
produce NO motion between connector and coax.
The noise is, I believe, a separate issue.
Have you attempted to locate potential antagonists?
Pull all breakers/fuses except for those necessary
to run the radio and engine. Does the noise go away?
Thank you,
Bill
Bob . . .
Message 2
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Subject: | RE: Request for some direction and advise |
At 11:32 AM 8/30/2015, you wrote:
I appreciate any assistance I can get. A difficult to hear some
transmissions is one thing but with the engine now involved, that is
a major problem.
Yeah . . . that tends to get your attention . . .
I will try and answer your questions in order.
This is a Lancair Legacy. Fiberglass not carbon fiber, although some
components are carbon fiber. No carbon fiber near the radio or
antenna installation.
The comm. Antenna is a Advanced Electronics antenna as is described here
http://www.aircraftspruce.com/catalog/avpages/antennasystems.php
The antenna is installed on the right side if the fuselage, inside
just behind the rear luggage bulkhead. The antenna is long enough
that it forms the shape of a "C" on the right side of the
fuselage. It extends from about the center line on the top to the
center line on the bottom. The bottom end of the antenna is very
close, within an inch, of one of the rudder cables. The rudder cable
does not connect to a ground due to the plane being fiberglass.
What are the chronological and service ages of
this installation. I.e. how long has the airplane
been flying and how many hours in that time. Noises
aside, I presume that the comm radio has performed
satisfactorily until now?
I just moved to the airport at Mesquite, TX on Friday. I have been
on their waiting list for 20 months. There is no radio shop on the
field and I have not yet met any builders there.
Unless they are related, I hope to find and fix the kicking off of
the autopilot and radio and the shutting down of the engine before
the static.
They are almost certainly unrelated. Noises in
receivers at selected frequencies have little
or nothing in common with energy from your transmitter
getting into places it doesn't belong.
The later symptom screams of broken coax shield
connection. Energy from your transmitter is supposed
to be 'piped' to the antenna . . . generally away
from potential victims before being gracefully launched
into the ether.
should your coax shield become ungrounded,
PARTICULARLY at the radio end, the entire
coax becomes a very disorderly antenna that
radiates stuff in and around the cockpit
with energy that might prove deleterious
to performance of the various systems. This
is a relatively rare condition but made a
greater risk in OBAM aviation where appliances
are NOT generally tested for immunity to strong
RF . . . a thing we do religiously in TC aircraft.
But even WITH proper homage paid at the altar
of the EMI gods, ALL systems have a limit as
to how much mischievous energy can be ignored.
The fact that you have TWO affected systems
suggests that the energy levels involved are
large and almost certainly associated with
loss of integrity in that 'pipe' . . . the
antenna feed line.
I will check the coax connectors to make certain that they are
tight. Are there any scenarios that come to mind where the keying of
the mike could cause other equipment to shut down?
They are probably manifestations arising from
a single cause.
Does this sound like voltage is being introduced onto the ground
system? Does it sound like a short somewhere? Surely the radio,
coax, antenna could not be putting out radiation that would shut down
the other equipment???
Under the WRONG condition cited above, the
coax is no longer a coax . . . and it easily
joins turns the best behaved transmitter into
a cockpit thug.
Other than the coax connectors, where would you look first? Second?
If we had my toolbox there, I'd first dummy load
the transmitter and note that the effect goes
away. I'd also put the antenna analyzer on
your comm antenna coax to confirm the cockpit
thug hypothesis. After that, it's pretty much
touchy-feely activities to deduce from whence
the pipe is leaking.
Bob . . .
Message 3
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Subject: | RE: Request for some direction and advise |
At 01:14 PM 8/30/2015, you wrote:
>I bought the radio and other electronics along about 2005. The FAA
>deemed the plane airworthy in Dec of 2010.
yeahhh . . . but . . .
> I now have 110 hours on it. The radio has always been a little
> squirrelly. I previously had problems
> with the autopilot dropping out but not shutting off. The
> TruTrak folks suggested I install a connector
> that has capacitors in it. That seemed to help for a while.
that was advice from TruTrak? to change the connector
on THEIR product? Given the technological roots of
this company I am . . . shall we say . . . mystified?
> Last year I had an instance where I could not hear ATC but they
> could hear me. Not caused by the hiss, but just dead air. I
> managed to find another controller that I could hear and he relayed
> what they were trying to tell me. I also can not pick up any ATIS
> until within 20 miles from any station that I have tried and I
> think that is supposed to be closer to 50 miles.
Clearly, not all is right with your antenna system
(presuming the radio is okay) . . . inability to
hear you is consistent with a severe transmission
line problem or perhaps even a broke antenna.
How hard would it be to remove your antenna for
bench testing?
>
>Several years ago, a friend checked the SWR on the antenna from the
>COAX connector at the radio and it was less than 2 at the time. I
>don't remember the exact number but it was low.
Normally, low SWR is a good thing but you need to
look at then antenna over its full range of
intended operation. "SWR" instruments are not
all necessarily golden either . . . I've pitched
a couple of cheapies in the trash after discovering
serious discrepancies in displayed readings versus
physical realities.
Bob . . .
Message 4
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Subject: | Opportunity alert |
Speaking of antenna analyzers, one of my work-horses
in the toolbox, the MFJ-259 is on sale right
now for a rather attractive price.
http://tinyurl.com/nke8w88
Not the top-dog analyzer by any means . . . it's
not a Bird or a Fluke . . . but it's of exceptional
value if you take care of it.
I used to rent one out but physical effects of
shipping and neophyte usage took a toll greater
than the rental fees. Had to give it up and buy
myself a new one.
Take care of this puppy . . . works good . . . lasts
a long time. EAA chapters ought to own one along with
a designated operator to go around and sort out antenna
problems for their membership.
Just saying . . .
Bob . . .
Message 5
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Subject: | Hydraulic Pump Start-Up Amperage |
My Lancair Legacy has a nominal 12 volt electrically powered hydraulic pump
that raises and lowers the landing gear. When the airplane has sat in the
hangar overnight, the hydraulic pressure bleeds down enough that the pump
turns on momentarily when I turn on the master switch. Master relays aren
=99t designed to make or break large electrical currents and I always
wondered if I was damaging it by hitting it with the large surge current f
rom the hydraulic pump turning on as the master relay closes.
A friend has a fancy little electronic box that measures electrical current
, sampling many, many times per second. Here is a trace of the current flo
w through a shunt between the battery and master relay. The blue trace sho
ws an 80 amp surge as the master relay closes and the hydraulic pump almost
simultaneously turns on. In this case, with the airplane on jacks, I had
the gear down and the landing gear selector switch in the =9Cup
=9D position when I turned on the master switch. That means that as soon a
s the master relay closed, the hydraulic pump also turned on to raise the g
ear.
The 80 amp surge lasts for about one or two milliseconds. About ten millis
econds later, the hydraulic pump obviously starts and the current surges to
155 amps. Landing gear extension and retraction each take about six secon
ds. In order to focus on the very brief surges, this graph shows only a fr
action of the first second.
The other two traces show the current draw from raising and lowering the la
nding gear in the customary manner, after the master relay has already clos
ed. Their two traces were overlayed with the first one.
I=99m not sure what this means. However, years of trouble free opera
tion for my airplane and many similar ones show that the master relay isn
=99t damaged by the hydraulic pump turn on surge.
Dennis
Lancair Legacy, 860 hours
Message 6
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Subject: | AeroElectric-List:_Hydraulic_Pump_Start-Up_Amperage? |
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Message 7
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Subject: | Re: Hydraulic Pump Start-Up Amperage |
>
>The other two traces show the current draw from
>raising and lowering the landing gear in the
>customary manner, after the master relay has
>already closed. Their two traces were overlayed with the first one.
>
>I=99m not sure what this means. However, years
>of trouble free operation for my airplane and
>many similar ones show that the master relay
>isn=99t damaged by the hydraulic pump turn on surge.
Yup, that's what they do . . . and it's
generally a good thing for battery master
contactors NOT to make them close against a heavy
load.
The fact that you've not had a problem may
be a classic demonstration of "who wins the
relay race". There is a natural delay time
between first voltage on a contactor to first
-touch in the bounce then some more time until
bouncing ceases.
It is possible that your pump controls have
sufficient energize delay time that they
don't begin to electrically hammer the battery
contactor until after it's reasonably stable.
Its a function many variables that can make
one configuration eat battery contactors while
others are not so problematic.
There are simple circuits you can put in
series with the gear-down pump contactor
to delay power to the coil by a few hundred
milliseconds or so. Totally transparent
to the system and crew but in SOME cases
may have a profound benefit to battery
contactor life.
I did the sketch for a Glasair owner about
20 years ago . . . didn't hear from him again
after he installed "The Mod". I'll dig
it up for you if you're interested.
Bob . . .
Message 8
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Subject: | RE: Request for some direction and advise |
I saw where someone else on the list a while back was discussing adding
that
connector to their TruTrak at the company's suggestion. It is supposed
to
keep RFI out as I recall.
The antenna is glassed in and not removable, I tried to attach it with
tape,
but I could not get it to stay in place so I just glassed it in. I do
have
a second antenna that I could try if I don't find anything with the
coax. I
only have a Volt-Ohm meter so I don't think I could bench test the
antenna.
Bill
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L.
Nuckolls, III
Sent: Sunday, August 30, 2015 5:18 PM
Subject: AeroElectric-List: RE: Request for some direction and advise
At 01:14 PM 8/30/2015, you wrote:
I bought the radio and other electronics along about 2005. The FAA
deemed
the plane airworthy in Dec of 2010.
yeahhh . . . but . . .
I now have 110 hours on it. The radio has always been a little
squirrelly. I previously had problems
with the autopilot dropping out but not shutting off. The TruTrak
folks
suggested I install a connector
that has capacitors in it. That seemed to help for a while.
that was advice from TruTrak? to change the connector
on THEIR product? Given the technological roots of
this company I am . . . shall we say . . . mystified?
Last year I had an instance where I could not hear ATC but they could
hear
me. Not caused by the hiss, but just dead air. I managed to find
another
controller that I could hear and he relayed what they were trying to
tell
me. I also can not pick up any ATIS until within 20 miles from any
station
that I have tried and I think that is supposed to be closer to 50 miles.
Clearly, not all is right with your antenna system
(presuming the radio is okay) . . . inability to
hear you is consistent with a severe transmission
line problem or perhaps even a broke antenna.
How hard would it be to remove your antenna for
bench testing?
Several years ago, a friend checked the SWR on the antenna from the COAX
connector at the radio and it was less than 2 at the time. I don=12t
remember
the exact number but it was low.
Normally, low SWR is a good thing but you need to
look at then antenna over its full range of
intended operation. "SWR" instruments are not
all necessarily golden either . . . I've pitched
a couple of cheapies in the trash after discovering
serious discrepancies in displayed readings versus
physical realities.
Bob . . .
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