Mailing List flyrotary@lancaironline.net Message #65505
From: Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Update on EMI problem.
Date: Wed, 15 Jan 2020 15:47:33 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
A ground issue somewhere. At battery, ground buss, ground strap to engine, ...
Corrosion or a loose bolt/nut.

Just guessing. But if it used to work and no changes were made before the symptoms appeared...

Yes, I know, easy to second guess the approach of someone else. :-)

Finn

On 1/15/2020 10:00 AM, Stephen Izett stephen.izett@gmail.com wrote:
Hi Bobby

I had no symptoms in the engine on tx until the last few weeks and only on controller A.
It misses as the mixture goes very lean.
In looking at the engine miss I realised the vertical speed was jumping on tx.
Not sure what brought about the change that started the symptoms.

Steve

On 15 Jan 2020, at 10:33 pm, Bobby J. Hughes bhughes@qnsi.net <flyrotary@lancaironline.net> wrote:

Steve,
  
I don’t recall if you are just seeing odd instrument readings or actual engine changes when you key the mic. At idle and ground ops I could almost kill my engine when transmitting on an SL30. The capacitors eliminated 90% of that problem. When I swapped the SL30 for a 430W it improved a little more.
  
Bobby
  
  
  
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Wednesday, January 15, 2020 8:06 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Update on EMI problem.
  
Hi Finn

I only went for them as I understood others had suffered a similar symptom and this was Tracy’s recommended fix.
I’ve got more ferrites coming and I’ll be putting these on all inputs to the EC2 and ADHARS and at the feed point of the antenna.
I’ll feedback what I discover.

Cheers
Steve

On 15 Jan 2020, at 9:02 pm, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

Did you trace the circuit? Any chance there's already caps on the board on your version of the EC2?

Again, I don't see the need for the caps. Especially because your problem was only with controller A.

I would start with temp input or serial input.

Finn

On 1/14/2020 11:23 PM, Stephen Izett stephen.izett@gmail.com wrote:
A frustrating few hours

I got down to the hanger this morning to look into the EMI in both the engine controller and EFIS.

First thing I did was reroute the radio coax so that instead of being in close proximity to many cables down the centre of the aeroplane instead down the very right hand side.
This increased the distance to various wire looms by ~450mm.

Prior to this change the symptom outside the hangar was from memory about a 300ft/min vertical speed on tx in the Skyview EFIS.

First test with radio tx after the reroute of coax inside the hangar yielded a "4 times worse" symptom in the EFIS! ~1300ft/min reading on tx.

I then tried the test outside and away from the metal hangar by 10m and the symptom was reduced to ~600ft/min and increase in symptoms of about 100% on original problem.
I then applied a clamp on ferrite to the cable loom entering the ADHARS unit from where the symptom originates.
On tx outside the hangar again the symptoms are far reduced by over 1/2.

So if I had left the radio coax where it was, the ferrite may have fixed the problem in the EFIS.
I have more ferrites on order and they appear to be very effective, so will use these to attenuate the RF entering the various pieces of equipment.
EMI trouble shooting is indeed a black art!!

I also removed the Engine Control unit and soldered 0.1uF ceramics across the outputs to earth of the MAP sensors of both A and B computers as specified by Tracy.
On reinstalling the Engine Control unit I was not able to start the engine!
It would fire but not run on either controller.
So spark and fuel are present, but not to remain running.

So the mod appears to have messed up the MAP sensing.
My initial thought was that the caps were actually resistors packaged wrongly but they measure open circuit.

So the few hours of mods and testing has been exceedingly frustrating, going backwards at every turn except for the 1 ferrite showing itself to be very effective.

I’m hoping my next outing will be very much more fruitful.
In the mean time I’ll ponder what could possibly cause both Computers in the Engine Controller to be u/s.
If I cannot discover my deliberate mistake. I’ll remove the caps and retest the Controller on Friday.

Cheers

Steve


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