Bendix Magneto A.D.

[pschmeltz]

I was told by my IA that I coming due for AD 96-12-07. Before I start pulling parts off the engine I wish to confirm that the AD applies to me.
The mags on my Continental C-145 are Bendix, model # 26LN-21F, s/n 458753 (LEFT); and model # 26LN-21, s/n 270174(right).

Thanks
Pat Schmeltz # 7538

[Azpilot]

I checked on the status, and it looks like it been superceded.

Along with that, looks like its only for Lycoming engines.

Here is the link: http://rgl.faa.gov/Regulatory_and_Guida ... -12-06.pdf

I do know that certain Magnetos require a 500hour rebuild and inspection.

[Bruce Fenstermacher]

Good news and bad news Pat.

First the AD does not apply to us any more.

Bad news is you should still pull your mags and inspect and service them like the AD still applied. It might not be so bad if a neglected mag just stopped producing spark, that is why we have two of them. But if a bearing fails and the mag freezes and teeth are sheared off the cam and mag gears and metal is spread through out the inside of your engine guess what your doing.

My mag with only 300 or so hours came apart at an idle on the ground. It made a heck of a noise just before and so I was right on the magneto switch. The mag shaft bent out of the way when the mag seized and with the engine shutting down didn't shear any teeth from either gear but I was sweeting bullets till an inspection could be done. Wish I'd pulled the mags at 250 hours like my IA wanted to just because.

[mit]

Come on Bruce! You should pull them every 50 hours if your crystal ball isn't working!

[Bruce Fenstermacher]

When my crystal ball isn't working I don't fly.

[blueldr]

Bruce and mit,
Funny you should mention a "Crystal Ball". I used to fly the Pacific on the "Dizzy Six" with a navigator who kept a rubber base mounted crystal ball prominently displayed on his desk in the plane. A real confidence builder.

[cessna170bdriver]

The mags on my Continental C-145 are Bendix, model # 26LN-21F, s/n 458753 (LEFT); and model # 26LN-21, s/n 270174(right).

Thanks
Pat Schmeltz # 7538

Probably just a typo, but if you have Bendix mags on a C-145, they both should be S6LN-21.

Here's the magneto AD's in my airplane's records:

82-20-01: A one-time AD to check heat treat of impulse coupling flyweights - doesn't apply to couplings with more than 300 hours time in service.

94-01-03 R2: Replacement of ignition coils and rotating magnets. (one-time)

94-06-09: Replacement of capacitor. (one-time)

96-12-07: Recurring ad on inspection of impluse couplings. To be accomplished prior to accumulation of 500 hours time in service since new, overhaul, or last inspection. It does apply to ALL S-20 series mags (and several others) with impulse couplings. S6LN-21 mags are included in the S-20 series. This AD has been superceded by 05-12-06.

05-12-06: Supercedes 96-12-07, and includes only mags on certain Lycoming engines, but like Bruce said, it would still be a very good idea to accomplish it on any Bendix mag with an impulse coupling. You definitely don't need any impulse coupling flyweights flying around loose in the engine. The mags on our small Continental engines are not difficult at all to remove an replace, so your mechanic should be able to perform the inspection in only a couple of hours, including reinstalling the mags and re-timing them to the engine. (It doesn't hurt anything to recheck timing at each annual anyway.) Cheap insurance, IMHO.

Miles

[Roesbery]

http://www.sacskyranch.com Has good explanations with pictures of what and why on bendix mags.

[GAHorn]

http://www.sacskyranch.com Has good explanations with pictures of what and why on bendix mags.

Here's their illustration of an impulse coupling which was allowed to go too long between inspections. The rivet failed on one of the counterweights and let it slip into the engine accy-case. See the missing rivet-head? It allowed the collar and weight to leave: