REFLECTOR: Ignition Noise
michalk
michalk at awpi.com
Mon Jun 11 14:21:24 CDT 2007
"power for the EI is in a shielded wire"
"the EI is grounded on the firewall"
Do you mean that your power path to the EI is battery->panel switch->EI?
And that this wire is a single conductor shielded wire?
How does your firewall ground return to the battery? If you patch in a
battery to your EI and do not send this power down the duct, does that
solve the problem?
You have two problems. First, your 430 is a receiver of this noise, and
second, your EI is generating this noise.
Fixing the noise generator usually makes other things work better, so
start there. The EI may have a large dV/dT, meaning a large voltage
spike in a short time causes magnetic flux lines and electrical fields
to be coupled into other things.
If your shield is connected in two places, remove the one closest to
your instrument panel. If the noise goes away, good, but you still have
a problem. The EI sent current down that shield because its a least
path of resistance back to your battery. Impedance goes up as frequency
goes up ... not just resistance. Your EI will be much happier giving
you a stronger spark if you fix the root cause of your problem. Look at
your ground path. No need really for shielded wires. The real need is
to have your power and ground wires twisted. Shielding is for
capacitive noise. If your power is balanced (no common mode noise) then
there is no energy to capacitively couple. Most likely you are
magnetically coupling the noise.
Don't fix the symptom, fix the problem. Use twisted wire, and if you
still want shielded, shield it at the EI(the radiator), not at the
instrument panel. Try to not ground your EI power to the firewall.
Even if the ground is attached to the firewall, the electricity will
like that path better, resulting in lower noise.
I'll bet you a beer that will fix it.
Ronnie Brown wrote:
> The headsets are grounded at the PS4000 intercom and no where else (but I
> will verify) The head set wiring is through the keel, EI is powered and
> grounded through the right side duct. Power for the EI is in a shielded
> wire and the shielded wire is grounded at the mag - by way of the panel.
> Now that I think of it, the EI shield is grounded twice! Might need to lift
> one end. Hmmm - thanks for the suggestions, Brian!
>
> The EI is grounded on the SS firewall as well as to the engine (but not
> using a braided wire - wonder if that would help?)
>
> Ron
>
> ----- Original Message -----
> From: "michalk" <michalk at awpi.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Monday, June 11, 2007 2:12 PM
> Subject: Re: REFLECTOR: Ignition Noise
>
>
> It's not a high frequency coupling.
>
> I would guess that your antenna shield is a ground path for your EI.
> Are your headset jacks insulated from the instrument panel? Or, do your
> headset wires share a common ground with your EI?
>
> Ron Brown wrote:
>> Actually, I have been chasing a spark noise in my Garmin 430 for a
>> several weeks. It is only coming in the 430, it goes away when I turn
>> off the Jeff Rose Electroair electronic ignition, it changes frequency
>> with engine RPM, it does not come in to the #2 com which is a lowly
>> Microair 760, it does not make noise if the antenna is disconnected from
>> the 430. Arrrggghhh!
>>
>> I have changed antennas from right to left, used a portable antenna,
>> bought new plugs and plug wires, connected the 430 to a separate
>> battery, swapped 430's with a friend, removed ground wires, cleaned and
>> retightened them, installed noise filters on the 430 and Electroair,
>> removed and inspected new plugs and new wires. Next I am going to
>> remove the timing unit from the distributor hole, spin the unit and see
>> if I can hear sparks, then try replace one high energy coil at a time.
>>
>> We are planning to fly to Colorado next week and I sure would like to
>> NOT hear sparking noises when I am receiving a far away aircraft or ATC.
>>
>> Any other suggestions from the collective???
>> Ronnie
>>
>>
>> ----- Original Message -----
>> *From:* Chuck Jensen <mailto:cjensen at dts9000.com>
>> *To:* Velocity Aircraft Owners and Builders list
>> <mailto:reflector at tvbf.org>
>> *Sent:* Monday, June 11, 2007 1:11 PM
>> *Subject:* Re: REFLECTOR: elevator cuff was Brake authority
>>
>> Ron,
>>
>> Thanks for the cuff description, I can visualize what you were
>> describing but since I don't have any, I was just curious. I was
>> suffering from cuff-envy until I realized it was fashionable not to
>> have 'em.
>>
>> P.S. Nice looking paint and trim job on the bird. Now that its all
>> painted up, I'm surprised you haven't found anything that you want
>> to change!
>>
>> Chuck Jensen
>>
>> -----Original Message-----
>> *From:* reflector-bounces at tvbf.org
>> [mailto:reflector-bounces at tvbf.org] *On Behalf Of *Ron Brown
>> *Sent:* Monday, June 11, 2007 10:41 AM
>> *To:* Velocity Aircraft Owners and Builders list
>> *Subject:* Re: REFLECTOR: elevator cuff was Brake authority
>>
>> Chuck,
>>
>> Don't have a picture - but I can describe them. It was a C shaped
>> piece that was installed on the leading edge of the Elevator - which
>> reduces the gap between the back of the canard and the elevator such
>> that when the elevator is down, the gap is reduced from what it
>> would be if the cuff wasn't there.
>>
>> It was installed on the inner half, span wise of the elevator.
>>
>> Ronnie
>>
>> ----- Original Message -----
>> *From:* Chuck Jensen <mailto:cjensen at dts9000.com>
>> *To:* Velocity Aircraft Owners and Builders list
>> <mailto:reflector at tvbf.org>
>> *Sent:* Monday, June 11, 2007 10:10 AM
>> *Subject:* Re: REFLECTOR: elevator cuff was Brake authority
>>
>> Does anyone have a photo of the "cuffs" that are being
>> discussed. I'm not sure I've ever seen the cuffs on the Velo.
>> You're welcome to email directly.
>>
>> Chuck Jensen
>>
>> -----Original Message-----
>> *From:* reflector-bounces at tvbf.org
>> <mailto:reflector-bounces at tvbf.org>
>> [mailto:reflector-bounces at tvbf.org] *On Behalf Of *Laurence Coen
>> *Sent:* Friday, June 08, 2007 12:39 PM
>> *To:* Velocity Aircraft Owners and Builders list
>> *Subject:* Re: REFLECTOR: elevator cuff was Brake authority
>>
>> Al,
>>
>> The way I understand it, the elevator cuffs were one of three
>> things done to address the deep stall problem. Your current
>> main wing was redesigned and the canard was shortened. The
>> cuffs are no longer needed. They were a modification for
>> existing Velocities at that time. I received cuffs with my kit
>> but never installed them. Their purpose is to increase the
>> stall speed of the elevator which would explain your high stall
>> speed.
>>
>> Larry Coen
>> N136LC
>>
>> ----- Original Message -----
>> *From:* Al Gietzen <mailto:ALVentures at cox.net>
>> *To:* 'Velocity Aircraft Owners and Builders list'
>> <mailto:reflector at tvbf.org>
>> *Sent:* Thursday, June 07, 2007 11:34 AM
>> *Subject:* Re: REFLECTOR: Brake authority
>>
>>
>>
>> I concur with Larry - 10KIAS makes a big difference.
>>
>> My canard stalls at 60KIAS with just me, 65KIAS with
>>
>> two people up front.
>>
>>
>>
>> I still have about half the width of the elevator cuff on
>> the elevators. It gives a very gentle pitch-buck at stall,
>> I’ve never felt a lack of elevator authority; and I never
>> have full aft stick on landing. However; would removing the
>> rest of the cuff reduce the stall speed?
>>
>>
>>
>> I have my ground idle set to about 500 RPMs (Lyc
>>
>> IO-540 with two mags) which is pretty much as slow as
>>
>> it will run
>>
>>
>>
>> My engine idle is about 850; that’s about 210 rpm on the prop.
>>
>>
>>
>> Al
>>
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