Magneto questions

Timbeck2

Timbeck2

Final Approach
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Timbeck2
My plane is down for it's annual...my first. Upon inspection, the mechanic said that I had "riveted impulse couplings and that it looked like the AD hadn't been done in years."

I was still reeling from the fact that my 5 year old ACK ELT 406 was fubar because it "went off" when the arm switch was selected.

So my question is: What do you do when you have magnetos with riveted impulse couplings? Can they be overhauled or should I just accept the fact that I need to buy a couple of new mags?

I knew this was going to be an expensive one because of the reputation of the mechanic that worked on it before I bought it. He cut a lot of corners and ignored a lot of things...this I found out after I bought the plane. Water under the bridge, spilled milk, etc.

I have an oil pressure hose that still has the 1969 data tag on it..the same hose that was on it when it rolled out of the factory.
 
Measure the
Timbeck2 said:
So my question is: What do you do when you have magnetos with riveted impulse couplings? Can they be overhauled or should I just accept the fact that I need to buy a couple of new mags?
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Measure it per the AD and worry about replacing when they don't pass.
 
Does the AD even apply? AD 96-12-07 was superseded by 2005-12-05 which drastically changed the applicability of it.


Applicability


(c) This AD applies to Teledyne Continental Motors (TCM) (formerly Bendix) magnetos that

have a magneto part number (P/N) listed in Table 1 of TCM Mandatory Service Bulletin (MSB) No.

MSB645, dated April 4, 1994, installed on Lycoming AEIO-540, HIO-540, IO-540, 0-540, and TIO-

540 series engines. These engines are installed on, but not limited to, airplanes manufactured by the

Cessna Aircraft Company, Maule Aerospace Technology Corporation, Mooney Aircraft Corporation,

The New Piper Aircraft Inc., and Raytheon Aircraft Company (Formerly Beech Aircraft Company).
 
Let's back up for a second. My mechanic mentioned the AD, I didn't look it up of haven't looked up which AD he's talking about. They're Bendix magnetos.
 
I don't think there is an AD that affects these installed on anything but the 540 engines listed above.
 
Forgive me for being ignorant on this because I am and is exactly why I ask the question of more learned folks like you guys. Does the FAA site list all ADs that apply? Link below but no way of knowing if it is a complete list.

http://www.faa.gov/regulations_poli...&sort=effectiveDate&direction=desc&startRow=1


Only AD I see on my plane is for grounding the magnetos and installing rubber nipples...heh heh...I said nipples.
 
Timbeck2 said:
Forgive me for being ignorant on this because I am and is exactly why I ask the question of more learned folks like you guys. Does the FAA site list all ADs that apply? Link below but no way of knowing if it is a complete list.

http://www.faa.gov/regulations_poli...&sort=effectiveDate&direction=desc&startRow=1


Only AD I see on my plane is for grounding the magnetos and installing rubber nipples...heh heh...I said nipples.
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Its not that simple. There are "appliance ADs" that are not airplane make/model or even engine make model specific and don't show up where you might expect them to.
 
If those mags haven't been off for an internal inspection for a long time, they should get looked at anyway.
 
bnt83 said:
I don't think there is an AD that affects these installed on anything but the 540 engines listed above.
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That's the way I've interpreted it. Furthermore, regardless of whether the affected 540s have Bendix or Slick magnetos there is an AD covering the impulse on those engines. The Bendix one is actually less frequent.

Dan Thomas said:
If those mags haven't been off for an internal inspection for a long time, they should get looked at anyway.
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Agreed. I wouldn't be surprised if the impulse won't pass Continental's recommended inspection if it has been on the plane for a while. But, the only way to know is to check.
 
Dan Thomas said:
If those mags haven't been off for an internal inspection for a long time, they should get looked at anyway.
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Last I checked, "inspection" wasn't a whole lot different from overhaul. Says me don't fix what ain't broke.
 
steingar said:
Last I checked, "inspection" wasn't a whole lot different from overhaul. Says me don't fix what ain't broke.
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Lost track of the number of times a 500-hour inspection has caught items that would have failed the mag before another 500 hours was up. Usually it was eroding points or wearing points cam/rubbing block that were shifting the E-gap toward a very weak or nonexistent spark. Once it was failing distributor gears. Another time it was a failing distibutor rotor bearing. Several times it was wearing carbon rotor brushes. Once was an internal arc that was eating at the rotor bearng block. At least one was a failing capacitor (its capacitance was way off).

Much cheaper to do this stuff at home than to find a dead mag at a fuel stop far away, maybe at some place that has no mechanic who can fix it. All it takes is for the impulse mag to get just weak enough that it won't spark for start, and there you are. Stuck.
 
Dan Thomas said:
Lost track of the number of times a 500-hour inspection has caught items that would have failed the mag before another 500 hours was up.

Once it was failing distributor gear.
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I know of one crash that killed two people I know because of this very problem. Occurred shortly after takeoff and caused a loss of power.
 
In all practicality, the 500 hr inspection is just looking at internal condition, cleanliness, and wear items (unfortunately, the impulse is a wear item). If done on schedule, it may be as simple as replacing the plastic cam, the brush & spring assembly, adding the tiny dab of cam grease, and re-setting the e-gap timing. Is like $10 in parts plus labor (all the parts above are PMA from tempest).

Of course ymmv!
 
thomasdr72 said:
In all practicality, the 500 hr inspection is just looking at internal condition, cleanliness, and wear items (unfortunately, the impulse is a wear item). If done on schedule, it may be as simple as replacing the plastic cam, the brush & spring assembly, adding the tiny dab of cam grease, and re-setting the e-gap timing. Is like $10 in parts plus labor (all the parts above are PMA from tempest).

Of course ymmv!
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yup....easy peasy for either Slick or Bendix.....badda bing....badda boom. :p
 
Of course, my mags are obsolete, so nobody makes makes the brush anymore... So, it's down to replacing the entire gear. Otherwise it wears out and drills a hole in the tab on the coil (unobtanium).

;-)
 
thomasdr72 said:
In all practicality, the 500 hr inspection is just looking at internal condition, cleanliness, and wear items (unfortunately, the impulse is a wear item). If done on schedule, it may be as simple as replacing the plastic cam, the brush & spring assembly, adding the tiny dab of cam grease, and re-setting the e-gap timing. Is like $10 in parts plus labor (all the parts above are PMA from tempest).

Of course ymmv!
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I have never seen a mag of either manufacturer that has 500 hours on it the will pass the inspection requirements. the rotor and distributor block are always eroded.
 

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Tom-D said:
I have never seen a mag of either manufacturer that has 500 hours on it the will pass the inspection requirements. the rotor and distributor block are always eroded.
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So wouldn't that be normal wear? Spark plugs wear too...

I've never seen distributor wear limits in either manufacturer's manuals, must be a "use good judgment" thing.
 
The difference between a 500 hour inspection and an overhaul is that with an overhaul you HAVE to replace parts that are still serviceable. They are being sent to Montana this morning.

I also found out that I won't be buying Slick mags if I have to buy new, as they cost more to overhaul than they cost new.
 
Timbeck2 said:
The difference between a 500 hour inspection and an overhaul is that with an overhaul you HAVE to replace parts that are still serviceable. They are being sent to Montana this morning.

I also found out that I won't be buying Slick mags if I have to buy new, as they cost more to overhaul than they cost new.
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You can probably thank the lawyers for that latter situation. Some years ago Slick seems to have decided that there was less liability risk selling new mags than selling the parts to overhaul them, so the full parts count now costs more than they charge for a new mag.

I did notice that a couple of sources, including Kelly Aerospace, sell overhauled Slick magnetos for about 30% less than a new one from Champion Slick. Maybe quality control has something to do with Champion Slick's decision.
 
Timbeck2 said:
The difference between a 500 hour inspection and an overhaul is that with an overhaul you HAVE to replace parts that are still serviceable. They are being sent to Montana this morning.

I also found out that I won't be buying Slick mags if I have to buy new, as they cost more to overhaul than they cost new.
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I replaced slicks with factory "rebuilt" TCM (Bendix) and was really happy with the quality they sent me. Plus they accepted the slicks for a $200 rebate IIRC.
 
Any one ever see the ICA's for a TCM or Bendix mag.?? read the opening statement then, para 3, 500 hour inspection criteria.
http://www.tcmlink.com/pdf2/sb643b.pdf

I'd wager 75% of the GA aircraft running TCM products do not comply with their ICA's Just my SWAG.
 
GRG55 said:
You can probably thank the lawyers for that latter situation. ...
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Uh oh....there will be a lawyer along soon who will want you to provide proof. Apparently they can be easily offended.

I sent them off this morning to Aircraft Magneto Services in Montana. They have a great reputation around here.
 
Tom-D said:
http://www.expaircraft.com/PDF/slick-overhaul.pdf

Para. 3.3.3 & 3.3.8 call as you will, the repair stations will replace if any metal is missing, and it always is.
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Inspect the brass electrode posts for signs of
physical wear. Replace block assembly as
necessary. During normal operation, the post
will experience an electrical-metal transfer with
the distributor gear electrode. This condition
is normal and not cause for rejection. (See
Figure 3.3.8.)

NFW would I buy distributor blocks every 500 hours.
 
  1. In addition to the requirements listed above, magnetos must be overhauled or replaced at the expiration of five years since the date of original manufacture or last overhaul, or four years since the date the magneto was placed in service, whichever occurs first, without regard to accumulated operating hours. Also at this time all related components, including the High Tension Ignition Harness, Starting Vibrator Assembly and Ignition Switch Assembly, must be inspected for airworthiness in accordance with the procedures contained in the latest revision of their respective Service Support Manual.
 
bnt83 said:
Inspect the brass electrode posts for signs of
physical wear. Replace block assembly as
necessary. During normal operation, the post
will experience an electrical-metal transfer with
the distributor gear electrode. This condition
is normal and not cause for rejection. (See
Figure 3.3.8.)

NFW would I buy distributor blocks every 500 hours.
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No worries, most operators here never get 500 hours in 5 years,. see overhaul requirements above
 
I guess I may be an exception. I haven't even owned it a year and I've flown over 135 hours in it.

I like to fly.
 
Timbeck2 said:
I guess I may be an exception. I haven't even owned it a year and I've flown over 135 hours in it.

I like to fly.
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The new will wear off and life will get in the way :)
 
Tom-D said:
It's nice to fly an unairworthy aircraft.
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Lol! Tom trolling again... I bet every airplane you have signed off in the last 10 years was unairworthy per your "today's definition".
 
Only work on or replace one magneto at a time. This is in case someone makes a mistake, like putting way too much grease or not connecting a wire correctly and if he made the mistake on both mags, well, you get the picture....Its not just a good idea, it's science!
 
bnt83 said:
Lol! Tom trolling again... I bet every airplane you have signed off in the last 10 years was unairworthy per your "today's definition".
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NOPE, my customers are better than that.

And remember. it's not my ICA that says that!
 
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