never had a mag quit on me before

[peevee]

ran the plane up and all was well, a large-ish drop but almost no differential.

take off roll seemed a little sluggish but I got 35" of manifold pressure. Heavy plane, warm day, high density altitude, not enough to make me even consider an abort.

once airborne I noticed the fuel flow surging a little, and noticed I thought I could feel the engine surging, don't know which I noticed first. Tried the electric boost pump in case it was a fuel issue, it wasn't.

landed and ran the engine up again to burn off fouling if present only to find the right mag completely inop. Go figure.

lots of little links in the chain there.

time to replace 2 bendix mags with just under 500 hours on them, anyone have experience with new vs overhauled? It's something like a $250 difference on each one. Seems the bendix mags are regarded pretty highly here and sounds like they run a long time usually?

Edited October 15, 2015 by peevee

[garytex]

I have found several times that it isn't wise to leave them unattended for more than 500 hours. And here is another datapoint. A good mag overhaul shop is plenty good enough. But find out who is good in your area.  Ask about pressuriZed mags if appropriate for your plane.

Gary

[peevee]

We'll find out where he sends them, he made it sound like it's a little harder to find a shop to do the BENDIX vs a slick but I really don't know much about it. 

[lamont337]

500 hours, but how many years?

i ask because mine were also less than 500 hours but over 10 years since OH. The large white plastic gear on the inside became yellow and brittle. Cracked right in half, working mag looked just as bad on the inside.

[peevee]

About 3 years

[Danb]

Must be in the air, my thread last Thursday I lost left mag completely, should have it back from o/h tomorrow, I had the 500 hr. Inspection at 477 hours these mags have a little over 600 hours on them. Once the left mag proves to be good I'm sending out the right mag for o/h, both went to the shop and I had the right one inspected again, then I'll hope to get another 400-500 hours out of them. Good luck..PV

[carusoam]

It's a tough environment for plastics. Hot and electro-static. Yellowing is similar to oxidation. Embrittlement over time can occur without the yellow color. Probably caused by Ozone generated by the high voltage discharge.

Any idea what polymer is being used for the plastic gear?

Best regards,

-a-

Edited October 15, 2015 by carusoam

[peevee]

Must be in the air, my thread last Thursday I lost left mag completely, should have it back from o/h tomorrow, I had the 500 hr. Inspection at 477 hours these mags have a little over 600 hours on them. Once the left mag proves to be good I'm sending out the right mag for o/h, both went to the shop and I had the right one inspected again, then I'll hope to get another 400-500 hours out of them. Good luck..PV

Thanks, it can always be worse! 

[Danb]

Yep, mine happened not far from home just had to get a ride back, I've been all over from Texas to Canada to Memphis in the past 25 hrs. and luckily it happened close to home you are correct!

[carusoam]

Theoretically, this would drive my decision to OH one at a time. They are both aging and wearing at the same rate.  I would prefer to have them 200 hours and two years apart from each other.  The level of stress generated by one mag going out is enough.

In the younger days, I thought it was normal to fly on one mag if the second one were to croak.  I think they meant to fly to the next airport and land. I must have missed something in 'young aviation buck 101’.

Best regards,

-a-

[Hector]

Just had both overhauled for $200 each.

[Danb]

Anthony that drove my decision even though the mag shop had both mags I decided on another inspection on the right mag and will send it out later, it wasn't driven by money but the fact I decided not to get both done at the same time I'm glad you had the same opinion an engineers mechanical decision is better than an accountants one. The shop did say that the left mag was in bad shape.

[Guest]

I wonder if when Lycoming and TCM build an engine if they put mags on with the same time or can provide them with different times?  For that matter radios, vacuum pumps and instruments would be better if they could be used before installing them in new airplanes.  The plane would surely be more reliable. 

Clarence

[carusoam]

Similar to asking a CB to OH an expensive device before it's time..?

Best regards,

-a-

[Shadrach]

Interesting. There are 2 repair stations on my field and both will service Bendix mags on site. It takes all of 2 hrs for an experienced MX to teardown and reassemble a Bendix mag. Did your mechanic open the mag up or just box it up?

Clarence, do you send all of your customers mags out for OH? Do you do any mag mx in house?

[peevee]

Interesting. There are 2 repair stations on my field and both will service Bendix mags on site. It takes all of 2 hrs for an experienced MX to teardown and reassemble a Bendix mag. Did your mechanic open the mag up or just box it up?

Clarence, do you send all of your customers mags out for OH? Do you do any mag mx in house?

He said he can't openopen the BENDIX mags up. He also didn't troubleshoot it, when I said what happened he said there was no way for that to happen unless the mag completely failed. 

These are pressure mags too 

[Parker_Woodruff]

Had the same thing happen in flight on an M20F. Noticed the plane would slow down, then speed up, then slow down. 

 

Landed and one mag was completely dead. 

[Mooneymite]

Anybody with MAG issues considering these folks?

http://electroair.net/

http://electroair.net/stc_ignition_kit.html

http://electroair.net/stc_ignition_kit2.html

 

 

 

 

[Danb]

I had no clue since I was stuck at another airport re. mag shops, mine were sent out to QAA i'll give a pirep after done.

[Shadrach]

He said he won't open the BENDIX mags up.

FIFY! I'm certain that he has all the tools necessary to open up the mag. A lot of guys are uncomfortable doing so. They feel additional concerns about liability. It's easier to send it out to someone else and shift the liability.

[Guest]

Interesting. There are 2 repair stations on my field and both will service Bendix mags on site. It takes all of 2 hrs for an experienced MX to teardown and reassemble a Bendix mag. Did your mechanic open the mag up or just box it up?

Clarence, do you send all of your customers mags out for OH? Do you do any mag mx in house?

Ross,

I can't/won't overhaul one, but I have no concerns in repairing or adjusting one.  Many times we end up doing some tweaking on mags done by specialty shops.  Not sure what the specialty is, so we don't use them anymore. 

 In some cases my customers want their mags sent to specific shops only, so we ship them out.  

Clarence

[Shadrach]

Ross,

I can't/won't overhaul one, but I have no concerns in repairing or adjusting one.  Many times we end up doing some tweaking on mags done by specialty shops.  Not sure what the specialty is, so we don't use them anymore. 

 In some cases my customers want their mags sent to specific shops only, so we ship them out.  

Why can't you OH? The kits are readily available. Is it TCCA thing?

[Andy95W]

Anybody with MAG issues considering these folks?

http://electroair.net/

http://electroair.net/stc_ignition_kit.html

http://electroair.net/stc_ignition_kit2.html

Yes.  Spoke extensively with them at Oshkosh and another aviation convention.  They have a good, well thought out product that really seems to do what it should.  I couldn't justify it based on the rather low number of hours I fly.  Aviation Consumer magazine did a write up on them and were also very impressed.

[jetdriven]

I spoke with Klaus at OSH 2 years ago and he thinks like I do. MP is one thing but RPM is the other half.  The electroair ignores RPM and you give up half of the potential gains.  

[philiplane]

If Bendix mags fail with relatively low hours, chances are the distributor block bushings were not lubricated per the manual at the last repair or overhaul. This involves heating the bearing to allow oil to soak into the bushing. Forgetting this step will make the distributor gear get hot and eventually it will strip a tooth, and the mag will no longer work.