Bendix Mag Coils

[wa4jr]

Well its my first annual with my "new" 170B and I find I have an airplane that has fallen victim to several "paper" annuals. One problem area is the massive number of ADs on the Bendix mags. I have two questions here. My IA says that I may be better off to just get a set of Slick mags and be done with all the AD work...especially since my Bendix units are 29 years old with 900 hours on them. I am told that most mags start to fail around the 1000 hour mark. Best to go with Slick mags or not? Since there is no entry in the logs for the Bendix mag AD inspection, my units will have to be opened and inspected for the proper coil. IF the coils need to be replaced, I hear that there are less expensive replacement units as an alternative to the Bendix brand. I have looked using the search feature, but cannot find any info on the less expensive coils for Bendix mags, even though I know I saw mention of this subject in a thread somewhere. Any advice from those going before me in this area would be greatly appreciated.

[kloz]

Most IA's that don't know how to work on Bendix Mags say to replace with Slicks. Ask yourself how many Slick Mags have you seen that are 29 years old. Most of the time when a Bendix Mag goes out you can buy parts and repair it for less than 200.00 or so. If the Slick goes out most of the time you have to replace it with yet another new one. I would not trade my Bendix Mags for new Slick Mags if it were two Slicks to one Bendix. JMO

[Bruce Fenstermacher]

For me it would come down to economics. If I could repair the Bendix for less than Slicks that is what I'd do. If the cost of repair of the Bendix came close to the price of the Slicks I'd would and have bought Slicks without hesitation. You usually get a new spark plug harness with the Slicks as well.
Most mechanics I talk to have now problems with the Slick mags produced today. Slick did enter the market a long time ago with a "throw away mag." When they finally quit after twice their intended life and were not repairable people were not happy and Slick got a bad name which still sticks with them today.

All Slicks made today and for some time now are repairable and they still have no ADs.

The Slicks I bought have been running without trouble for almost 8 years and 1000hrs.

This issue, Slick / Bendix seems to be much like the Car Gas / Av Fuel or Ford / Chevy debate. You will get favorable arguments on both sides. I must say using Carl's logic of sticking with the 29 year old design doesn't hold water. Are we still driving model T's or have we move on to those new fangled models which may actually get us where we need to go without changing a flat.

[kloz]

I must say using Carl's logic of sticking with the 29 year old design doesn't hold water. Are we still driving model T's or have we move on to those new fangled models which may actually get us where we need to go without changing a flat.


Maybe But! We are still flying old airplanes. Sometimes change is just cheaper not better. When Cessna started building the 172 again they didn't change the basics. A lot of the new things they used have lots and lots of AD's. But you are correct in one way. Everyone looks at these things from a different view. JOM

[Tom Downey]

The coils for Bendix mags cn be bought at:

http://www.aircraftspruce.com/main.html

Most mechanics the you meet inthe field done want to mess with overhauling any MAGs. the pubs and tools for doing the overhaul are scarce.
When Bendix mags are overhauled using the correct parts the only AD that is re-occuring is the impulse coupling, every 500 hours. that is 10 years flying for the average pilot.
OBTW
the coils are less than $100.00

[wa4jr]

After my IA took the Bendix mags off and opened them up, cleaned out all the tons of goey junk and checked the wear, all appears just fine. The ADs had all been complied with, proper coils and impulse couplings...just the scatterbrain that did the work to comply with the ADs never bothered to enter his work in the log. Proper stampings were not on the ID plates indicating the ADs had been complied with either. Why do some mechanics do this???? Do the work and then don't document it....leaving another owner years later to have to open up the affected units and verify AD compliance. My carbureter (sp?) was not stamped properly for the one-piece venturi as well...even though log indicated the work had been done. Soooo we have to open the carb up to verify AD compliance. Well, the mags did have to be opened up for the 500 hour AD...which was overdue by 400 hours!

Had the price to repair the Bendix mags been significant, my IA recommended a Slick kit to do away with all the ADs. Slick only has one AD out vs about five for the Bendix. But I'll run the old Bendix units for at least another year now! Whew...dodged that $1400 bullet this year

[lowNslow]

Slick has a pretty good upgrade deal on there mags. If you switch to Slicks you get two new mags, new ingnition harness, and new spark plugs for about $1000.00 after rebate and your Bendix cores.

[Andrew D.]

Why would your mechanic say you have to " open up " your mags or your carb to check for AD compliance ? This can be seen easily without disassembly .

Andrew

[zero.one.victor]

Bruce,no offense,but I had to laugh reading your comment about sticking with a 29 year old design or going with the "new-fangled design"! Mags are way old technology,like almost everything in general aviation except GPS--calling Slicks new-fangled is like calling a stone axe cutting edge technology (get it?) just because you had it powder-coated!
That said,I went with Slicks at engine overhaul 2 years ago because my overhauler recommended it. I got 2 NEW mags and NEW harnesses for about what it would have cost to have my old Bendix mags overhauled. I had to trade in the Bendix mags to get the discount price*, but kept the Champion harnesses which were only a couple years old, and sold them for $125 so I think I came out ahead. NO Ad's on the Slicks.
* I figure Slick must be doing this to get the Bendix mag cores off the market,and so take it over by attrition.


Eric

[Bruce Fenstermacher]

Eric I realized that about the mag technology as I was writing and perhaps should have said new company but I liked the way what I wrote sounded.

I've talked to the Slick rep and he will tell you they are collecting the competition for exactly the reason you state.

BTW as I recall the one Slick AD is for a few serial numbered units because of a manufactering defect which has long been fixed and most if not all of the effected mags have been recovered and out of use.

[wa4jr]

Andrew, my IA had to open up the mags to visually verify the correct parts were installed as mandated by the numerous ADs over the years. Evidently each AD had a directive to "stamp" the ID plate on each mag as the new parts were installed. No AD stamp was viewable and no documentation was in the logs so there was no choice other than opening up the units to verify AD compliance. As for the carb, I suppose you could remove the airbox and check for the one-piece veturi from the bottom...but once again this would have been an unnecessary step had a mechanic years ago spend 60 seconds to properly "stamp" the ID plate on the carb indicating AD compliance. The carb had to come off anyway to clean it up and check out the service limits...had been in service since 1974 and the throttle shaft was sloppy as well as the accelerator pump plunger. Lucky for me everything cleaned up well and was within service limits...but I'll have to start thinking about a replacement within the next year or two.

[mit]

Andrew, my IA had to open up the mags to visually verify the correct parts were installed as mandated by the numerous ADs over the years. Evidently each AD had a directive to "stamp" the ID plate on each mag as the new parts were installed. No AD stamp was viewable and no documentation was in the logs so there was no choice other than opening up the units to verify AD compliance. As for the carb, I suppose you could remove the airbox and check for the one-piece veturi from the bottom...but once again this would have been an unnecessary step had a mechanic years ago spend 60 seconds to properly "stamp" the ID plate on the carb indicating AD compliance. The carb had to come off anyway to clean it up and check out the service limits...had been in service since 1974 and the throttle shaft was sloppy as well as the accelerator pump plunger. Lucky for me everything cleaned up well and was within service limits...but I'll have to start thinking about a replacement within the next year or two.

If the mag was not in the applicable S/N range there was no stamp needed.

[zero.one.victor]

John,beside the venturi issue,I think there's a carb AD (or at least a service bulletin) to change to a metal float. This is also a "stamp job" on the carb data plate,but maybe they did-maybe they didn't. When my mechanic did my cargas STC years ago,he checked to be sure the carb was stamped to indicate a metal float had been installed,as required by the cargas STC. It was stamped. But when my overhauler tore the carb apart 2 years ago, he said it did NOT have the metal float.
So even if something is documented,doesn't necessaril;y make it so.

Eric

[Tom Downey]

That is because parts get changed.

[GAHorn]

Some of these msgs reveal the ongoing mx problems mentioned elsewhere.
Sometimes a person not properly licensed will perform maintenance and since they don't have the proper certificate,...they don't log the work. (This is one of the most egregious acts in the eyes of the FAA. They consider work performed and not logged as more dangerous than no work performed.)
Sometimes, an accessory such as a mag or generator, etc. is improperly logged in the aircraft logbooks,...and then the engine is later sold/installed on a different airplane. The engine's logbooks accompany it to it's new airplane/owner. It's logbooks do not mention the work performed on the accy.
And sometimes a simple matter of lack of tools (stamping dies) or lack of attention to detail in performing the instructions ... result in not properly performing the AD and logging the work.