Group Poll: How many hours between mag overhauls?

Hey TC... 200 Series Bendix shower of sparks type.

Jim

wrote in message
...
On Wed, 20 Apr 2005 06:26:43 -0700, "Jim Burns"
wrote:

To the group: At how many hours do you rebuild or replace your mags? or
do
you wait for a problem to arise first?

Jim


Back to you: What type/manufacturer of magneto on what engine
installation?

The answer varies from magneto to magneto and installation to
installation.

For instance, I can't recall ever doing a manufacturer-mandated (as
opposed to FAA mandated) 500 hr inspection on a Slick magneto that
couldn't use a set of new points and the crap dug off of the
distributor block.

I can't recall ever doing a 1000 hr inspection on a Slick magneto that
didn't need a set of new points and a new distributor block.

Unless prices have changed a big bunch, you can't buy a new set of
points and a new distributor block + an hour or so of labor for much
less than the price of a new Slick magneto.

I would really not get into the practical maintenance requirements for
a dual Bendix/TCM magneto, given a choice.

TC

On Mon, 25 Apr 2005 05:36:29 -0700, "Jim Burns"
wrote:

Hey TC... 200 Series Bendix shower of sparks type.

Jim


Visual inspection of points every 100 hrs/12 months whichever came
first with point replacement based on condition noted. Doesn't take a
rocket scientist to pop the contact cover screws and notice that the
points are worn/gap out of limits (too big if the contacts are eroded,
too small if the plastic cam follower is worn).

1000 hr/5 year internal lubrication following the TCM/Bendix
recommended procedures.

Overhaul/replacement at normal TBO interval for the engine they were
mounted to.

As others have mentioned, if the 500 hr impulse coupling check was
mandated, the impulse mag/mags were pulled for coupling inspection,
internal timing check/point replacement (again determined by
point/follower condition).

Lycoming SI 1291 (as I recall) addresses more frequent inspection of
the distributor block on magnetos used primarily at high altitudes. I
don't have a copy of it handy, and do not remember the hourly
requirements.

TC

I guess I have followed the practice mentioned by others... if they are
Bendix, check the points & clean out at 500 hours while doing the
impulse coupling check. Follow SB599X

The old slicks with the plastic cam needed attention every couple
hundred hours. Newer ones seem to last like the bendixs.

So I find points with a little wear at 500 hrs, but OK; at 1000 hours,
usually replace them and they are good to go till tbo.

On the slicks, the dust from arcing in the towers will often short
out the distributor caps. So it's a good idea to clean the distributor
caps while they are out.

Sure there are two. What do you do when you fail a mag check
in Bum---- Nebraska on a Sunday?

Bill Hale A&P

One trick I have used to minimize the electrical stress on a magneto
and the related ignition harness is to make sure the plugs are gapped
to the minimum permissible gap. This minimizes the chance of
encountering a random failure from high voltage.