Effect of harness misrouting to top vs. bottom cylinder

[flyer338]

On 12/11/2019 at 7:47 PM, kortopates said:

I have never seen that on a O-360. But it is common with electronic ignition but just on experimental engines to my knowledge. I would be curious to where the approval for that comes from since that's news to me. Let me guess that your Mag RPM drop has never been even?   But you can really only see that with a engine monitor or digital tach,  yet I would expect the left mag isolated will have a bigger drop than the Right mag. 

With Electronic ignition it makes sense to do that,  by having the electronic ignition fire the bottoms since the higher voltage of the EI can still fire a dirtier bottom plug better than a conventional mag. But with 2 conventional mags it doesn't seem like a good idea when you lose the right mag and can only fire your bottom plugs that are not likely to be in the best of shape - the odds of finding yourself running on less than 4 cylinders is much higher than with a conventional arrangement. 

Here is a diagram of what the O-360's ignition harness is as they came from the factory, as mentioned the conventional routing  on most engines is opposite of this.

The previous owner of my J model had an EIS-41000 electronic ignition installed when he overhauled the A3B6 engine. The left mag fires all of the top plugs and the EIS installed in place of the right mag fires all of the bottom plugs

[Ragsf15e]

On 12/11/2019 at 4:13 PM, DXB said:

I'm aware that the left mag on my lycoming O-360-A1D is supposed to fire the top plug on #1 and #3 and the bottom plug on #2 and #4.  What is the purpose of splitting it up top vs. bottom plug for each mag this way?

I'm asking because during install of a Surefly mag, which requires changing out my Bendix harness for a Slick harness, the A&P noted that my harnesses were misrouted - i.e. the left mag was serving all the bottom plugs and the right mag serves all the top plugs. So now he has to mess with the right mag and reroute the right harness as well .  I bet it's been this way since the engine was overhauled in 2000, and no one ever noticed.  What adverse effect could this have had?

I just had a Surefly installed and my mechanic found that my engine had the “optional” wiring arrangement too.  I already bought a new slick harness for the left side with the standard wiring, now maybe need a new right side bendix with standard wiring.  More complicated than it should be.  I’m hoping he can just move the leads, but as everyone said, they’re labeled and cut to length.  Ouch.

[N201MKTurbo]

1 hour ago, Ragsf15e said:

I just had a Surefly installed and my mechanic found that my engine had the “optional” wiring arrangement too.  I already bought a new slick harness for the left side with the standard wiring, now maybe need a new right side bendix with standard wiring.  More complicated than it should be.  I’m hoping he can just move the leads, but as everyone said, they’re labeled and cut to length.  Ouch.

If they fit, then relabel them, if they don’t, then ouch!

[Ragsf15e]

2 hours ago, N201MKTurbo said:

If they fit, then relabel them, if they don’t, then ouch!

Yeah that’s the plan.  He’s a good mechanic.  Willing to work with stuff like this, but also willing to tell me to get the right parts when necessary.  I always trust guys more who tell me I need new/fixed items after they’ve told me not to fix something else a few times.

[Ragsf15e]

17 minutes ago, pmccand said:

There is an experimental Vans RV in a hangar a couple doors down with brand "X" electronic ignition system installed on both sides.  This pilot did not notice the alternator warning light after the Alternator failed due to a broken belt, so he kept flying while the battery continued to supply the electronics... until the battery wore out and the electronic ignition system quit producing sparks.  Needless to say, he had to ditch the plane in a field for a total loss of the aircraft.  He would have been fine if he would have kept one of the original magnetos instead of a dual electronic system as they do not require external system power to produce sparks.  So my question here is do either the Surefly or Electroair systems require battery or alternator systems to keep running?  Are either approved for complete replacement of the stock Slick or Bendix systems that don't require electrical power for operation?

They both require the battery or alternator, but they are also both only approved to replace one mag on certified airplanes.  If you lose the whole electrical system, you will still be running on one mag.  There is a company testing emags that self generate like a mag, but those are still experimental.

Most of the benefits of electronic ignition is recognized with only one mag replacement and the other a “wasted spark”.  Supposedly.

[ArtVandelay]

There is an experimental Vans RV in a hangar a couple doors down with brand "X" electronic ignition system installed on both sides.  This pilot did not notice the alternator warning light after the Alternator failed due to a broken belt, so he kept flying while the battery continued to supply the electronics... until the battery wore out and the electronic ignition system quit producing sparks.  Needless to say, he had to ditch the plane in a field for a total loss of the aircraft.  He would have been fine if he would have kept one of the original magnetos instead of a dual electronic system as they do not require external system power to produce sparks.  So my question here is do either the Surefly or Electroair systems require battery or alternator systems to keep running?  Are either approved for complete replacement of the stock Slick or Bendix systems that don't require electrical power for operation?

He also would have been fine if he noticed the alternator warning light or had an engine monitor flashing voltage readings.


Tom

[DXB]

17 hours ago, Ragsf15e said:

I just had a Surefly installed and my mechanic found that my engine had the “optional” wiring arrangement too.  I already bought a new slick harness for the left side with the standard wiring, now maybe need a new right side bendix with standard wiring.  More complicated than it should be.  I’m hoping he can just move the leads, but as everyone said, they’re labeled and cut to length.  Ouch.

See if you can get the new slick harness run where the current left bendix harness goes.  My A&P started redoing both sides before I could find the right option here and intervene.  

11 hours ago, pmccand said:

There is an experimental Vans RV in a hangar a couple doors down with brand "X" electronic ignition system installed on both sides.  This pilot did not notice the alternator warning light after the Alternator failed due to a broken belt, so he kept flying while the battery continued to supply the electronics... until the battery wore out and the electronic ignition system quit producing sparks.  Needless to say, he had to ditch the plane in a field for a total loss of the aircraft.  He would have been fine if he would have kept one of the original magnetos instead of a dual electronic system as they do not require external system power to produce sparks.  So my question here is do either the Surefly or Electroair systems require battery or alternator systems to keep running?  Are either approved for complete replacement of the stock Slick or Bendix systems that don't require electrical power for operation?

Wonder which system he had - all the ones for the experimental world that depend on electrical power for both mags require a second battery be installed for backup. The alternative for them is the Emag, which has an internal alternator that makes it independent of ship's power.  The certified Surefly and Electroair depend on battery also but replace only one mag. 

[ijs12fly]

On 1/5/2020 at 1:12 AM, ArtVandelay said:

He also would have been fine if he noticed the alternator warning light or had an engine monitor flashing voltage readings.


Tom

This makes one consider the failure scenarios for having Dual Elec Ign if you plan on flying across large bodies of water -  US to Europe ....