BC12D Cowling Fairings for Screened Plugs.

[3Dreaming]

Re: BC12D Cowling Fairings for Screened Plugs.

Thanks, Tom. I understand which mags fire which set, just wasn't sure if I was accomplishing anything by rotating plugs the way I was doing it. I have a specific pattern I do each time. Thanks for the info!

Just remember that the pattern needs to eventually move each plug to each cylinder for each mag.

[Guest]

Re: BC12D Cowling Fairings for Screened Plugs.

Marty,

This info may help, not sure.

I was wrong earlier, you don't have to shift them all in the same "direction" in the firing order but merely swap a plug with the a cylinder that it adjacent to it in the firing order.

I believe the firing order is 1-3-2-4.

Given that is true then;
Moving plug from 1 to either 3 or 4 will change it's polarity.
Moving plug from 2 to either 3 or 4 will change it's polarity.
Moving plug from 3 to either 1 or 2 will change it's polarity.
Moving plug from 4 to either 1 or 2 will change it's polarity.

Moving to top or bottom will not make any diff to polarity if LH and RH mags are the same part number.

Dave

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

Thanks, guys. I will make sure I am doing this.

[PA1195]

Re: BC12D Cowling Fairings for Screened Plugs.

Not a new idea but years ago a mechanic friend gave me a spark plug tray (http://www.championaerospace.com/pro...park-plug-tray) marked with the rotation sequence. After removal and cleaning it's a simple matter to shift them in the tray then reinstall.

Gary

[Guest]

Re: BC12D Cowling Fairings for Screened Plugs.

Good idea Gary, that makes it simple to do.

[3Dreaming]

Re: BC12D Cowling Fairings for Screened Plugs.

The marked tray doesn't work when dealing with the 4 top and 4 bottom scenario.

[PA1195]

Re: BC12D Cowling Fairings for Screened Plugs.

I works however you mark it...TCM's suggested change scenario or personal preference.

Gary

[3Dreaming]

Re: BC12D Cowling Fairings for Screened Plugs.

I works however you mark it...TCM's suggested change scenario or personal preference.

Gary

What I was trying to say is, following the markings on the tray doesn't work when your 4 top plugs need to stay on the top and your 4 bottom plugs need to stay on the bottom.
I have a tray and rotation sequence that I use, but sometimes a special airplane requires a special procedure. About half of the airplanes I work on anymore just get a plug change at inspection time instead of cleaning and rotation.

[PA1195]

Re: BC12D Cowling Fairings for Screened Plugs.

Ok I see now what you're saying about special circumstances. Good point on the exceptions to be paid attention to.

My problems with plugs have had to do more with top vs bottom fouling and not so much wear induced by changes in polarity. The cleaning process has not been my favorite as sometimes unless careful the blaster contains abrasive that doesn't get flushed from the plug core until they're back in the engine. Plus excessive abrasion can wear the sharp edges of the electrodes that promote good spark. Then there's the question of ceramic core pitting and wear. Unless the cleaner does a breakdown test under pressure that's meaningful who knows how good an older plug is until it's flown?

Sometimes it's just more dependable to periodically change them out if flown over remote areas or in and out of tight spots.

EDIT: Some cleaning tips: http://www.tempestplus.com/Portals/0...y%20061212.pdf

Gary

[Guest]

Re: BC12D Cowling Fairings for Screened Plugs.

Ok I see now what you're saying about special circumstances. Good point on the exceptions to be paid attention to.

My problems with plugs have had to do more with top vs bottom fouling and not so much wear induced by changes in polarity. The cleaning process has not been my favorite as sometimes unless careful the blaster contains abrasive that doesn't get flushed from the plug core until they're back in the engine. Plus excessive abrasion can wear the sharp edges of the electrodes that promote good spark. Then there's the question of ceramic core pitting and wear. Unless the cleaner does a breakdown test under pressure that's meaningful who knows how good an older plug is until it's flown?

Sometimes it's just more dependable to periodically change them out if flown over remote areas or in and out of tight spots.

EDIT: Some cleaning tips: http://www.tempestplus.com/Portals/0...y%20061212.pdf

Gary

I agree Gary.

I only do one annual a year and it son my plane but I do not clean plugs, just inspect.

Dave

[PA1195]

Re: BC12D Cowling Fairings for Screened Plugs.

This thread has taken a turn from fairings to maintenance and I apologize for the final distraction.

But as long as I'm being bad I might note that bad plug connections or slightly misfiring plugs can sometimes be heard on radios in flight. One of my jobs was tracking fish and wildlife that had low power transmitters attached. The plane's antennas were high gain and somewhat directional; the tracked transmitters often weak so a low background noise was essential.

When one or more spark plugs started fouling (we flew at low power 50-60%) or a lead wire started talking (mainly at the wire connector to plug connection) the noise floor on the plane's AM radios and tracking equipment (~150Mhz) would audibly increase. I could isolate the mags and then watch the differential cylinder EGT spread on a multi-cylinder gauge. A bad plug or connection often changed the EGT temp versus others on that mag. Not 100% diagnosis but often it worked to detect an ignition problem providing the fuel injector flow was similar.

Gary

[Mick W]

Re: BC12D Cowling Fairings for Screened Plugs.

Since fitting the Ercoupe Cups , the Engine developed a misfire , & after some major investigation , the problem was found to be one of them arcing out onto the Dust Cap , beware not to screw them right in , & only just enough to get Wire locking in !!!!!.

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

Not sure what plugs you are using, but mine screw in all the way and do not arc.

[Guest]

Re: BC12D Cowling Fairings for Screened Plugs.

Where is the copper washer supposed to go on these installations?

Under the plug or under the cup?

Dave

[Hank Jarrett]

Re: BC12D Cowling Fairings for Screened Plugs.

The cup replaces the washer.

Hank