Look at the mags, please

kmead

kmead

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kmead
This magneto arrived on a customers Mirage, it flew non-stop from CA to KS at 23,000 ft. No problems were noted, a perfect flight.

I always open the magnetos at every annual. Look at the annual inspection guide the shop is using, most list inspection items like-inspect contact points, distributor block, and lubrication of the felts requiring opening the mag. The so-called 500 hr inspection is not enough. You wouldn't believe the problems we find.

I cant believe how expensive it would be to get 5 people home from Dodge City KS to Louisville KY on a Sun. afternoon when the plane breaks down. It's a lot cheaper to install new mags each year if the shop wont open them up for a simple inspection.

Ranting, Kevin

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kmead said:
This magneto arrived on a customers Mirage, it flew non-stop from CA to KS at 23,000 ft. No problems were noted, a perfect flight.
Click to expand...

Looks like there was spark all over the place in that one. At 23,000 feet this mag should have been pressurized off the turbo. Was it? Low ambient pressure within the mag will allow spark to fly everywhere, since air is an insulator and the lack of it will do some of this.

Aside from that, I agree regarding regular inspections. We usually do them at 500 hours, finding that the points will normally go 1000 hours. With several recent Slick SBs we've had them apart a lot more than that.

Dan
 
N801BH said:
Very hard to believe it ran perfectly....:frown2::nono:
Click to expand...

NO,,,,,,, It just shows how really bad they can get and still run OK. Very dependable system.
 
The incoming pressure check of the mags and induction system showed no problems. Loss of pressure will cause engine roughness at altitudes above 12,000 ft, ROP or LOP. Full power mag checks were also good. We have a lot of moisture problems on the pressurized mags. What really starts the problem is that the gears shed material that plugs the vent orifice. The mag can't purge the moisture from the mag leaving the inside wet and easier to arc over. The moisture and the ozone gas forms an acid that attacks the plastic and metal parts too (self destruct). We really need a solid state ignition system.

Kevin
 
I looked again at those pics, and see that you had a problem outlined in a Slick Service Bulletin, SB 3-08A. You can see it here on Lycoming's site:
http://www.lycoming.textron.com/support/publications/service-bulletins/pdfs/SB584B.pdf

The worn carbon brush and improperly positioned coil tang are the giveaway. A bent tang causes the brush to wear, and carbon dust gets all over everything and starts a flashover process.

Dan
 
Can't imagine full power LOP mag checks would have been even close to acceptable. Is the plane run that way?
 
so much like one I opened recently:
 

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