Group Poll: How many hours between mag overhauls?

[Jon Kraus]

Our Mooney has a 500 hour recurring AD for inspecting the Impulse
Coupler. While they have it off they will inspect the points and
condensers and replace worn ones. Our left mag was out of time by 5
degrees so they had to remove the magneto anyway.

Jon Kraus
PP-ASEL-IA
'79 Mooney 201

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
>
>

[Aaron Coolidge]

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?

My airplane has Bendix mags, which as Jon pointed out have a recurring
AD for impulse coupling inspection. I think it's every 400 hours, though, but
I can't remember. So, every 400 hours the impulse mag gets an internal
inspection. I have the non-impulse mag inspected at the same time, although
not strictly required. It makes me feel better while I'm flying night IMC over
the Chesapeake Bay. Most of the time nothing needs repair, although the
first time we found some "superceded" parts that were replaced.

If I notice different mag drops and the plugs are OK I have the mags looked
at, as the timing may have changed. Every 100 hours I check mag to engine
timing when I clean the plugs.

Keeping the mags well tuned makes the engine start much easier, too.
--
Aaron C.

[Jim Burns]

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

[tom418]

I have the mags (Bendix) overhauled at the same time the impulse couplings
get done. (Seneca)
"Jim Burns" > wrote in message
...
> 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
>
>

[[email protected]]

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?
>
When the left comes off for the impulse coupler inspection, I have
both sent over to the accesory shop. Rather than having them
overhauled, I have the shop "inspect and repair as necessary". It's
much less expensive than an overhaul. If the mags are in good shape, I
see no need to go the full overhaul route and replace a bunch of parts
that are working just fine. Most of the time, the mags come back with
little or no work having been done. If they were really getting rough,
the shop would let me know and I'd OK an overhaul. My current set of
(Bendix) mags went about 1200 hrs. between overhauls.


John Galban=====>N4BQ (PA28-180)

[Mike Spera]

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
>
>
500 hours. Usually, one needs some parts and the other needs to be
replaced. Slick mags in a Cherokee 140.

Mike

[Doug]

I replaced the Slick mags on my Husky's Lycoming O-360 after 2000
hours, though the plane didn't run any better with the new ones. Seemed
like it was time for new ones. They work great too. Mechanic managed to
miss-time them at first go around. Had trouble with his buzz box. It's
tight back there, hard to adjust them.

[Roger]

On Thu, 21 Apr 2005 00:51:16 GMT, Mike Spera >
wrote:

>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
>>
>>
>500 hours. Usually, one needs some parts and the other needs to be
>replaced. Slick mags in a Cherokee 140.
>

I've put a 1000 on them and I'd have to dig out the log books but I
believe they were new with the engine. That'd make about 1300
currently. Still workin' good.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>Mike

[Robert M. Gary]

"Jim Burns" > wrote in message >...
> 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


I have them opened every 500 hours in my Mooney. I don't have the AD
because my mags were replaced. However, I've never actually O/H'd
them. I have them opened, inspected and replace points, etc. The shop
has never found any issues worthy of an O/H. Figure 3-4 hours per mag.

-Robert

[[email protected]]

MAINTENANCE INTERVALS FOR ALL TCM AND BENDIX AIRCRAFT MAGNETOS
see SB643B
http://www.tcmlink.com/servicebulletins/index.cfm

i use 500 hr for bendix & slick for service
for Bendix D-2000 450 to 500 for service
jon

[Doug]

You have two of them. If one fails you can continue to fly on the
other. Best thing to do is replace ONE. Then you have one new one and
one old one. I consider mags to be 2000 hour lasting accessories, or
replace when they fail. You could easily argue that you don't have to
replace them until you rebuild the engine. It really is up to you. But
with mags, you do have a backup if one fails and the likelyhood of both
failing at once is small.

[Newps]

Doug wrote:

> You have two of them. If one fails you can continue to fly on the
> other. Best thing to do is replace ONE.

Better than replacing two?

[tony roberts]

My Slicks gave a problem on left mag drop at 1200 hrs and were repaired.
Until the problem, mag maintenance hadn't even occured to me - there's
just too many things to be aware of in aircraft ownership - I guess that
one just slipped under the radar.

Tony
--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE

In article >,
"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

[[email protected]]

O-320 that had a brand new pair of Slicks installed when the engine was
field-overhauled 6 years ago. At the 500 hour mark last annual, we
pulled them and examined them. My A&P said they still look like new
inside.

[Dave Stadt]

"tony roberts" > wrote in message
news:nospam-A30BC4.22543423042005@shawnews...
> My Slicks gave a problem on left mag drop at 1200 hrs and were repaired.
> Until the problem, mag maintenance hadn't even occured to me - there's
> just too many things to be aware of in aircraft ownership - I guess that
> one just slipped under the radar.
>
> Tony

Slick says at 500 hours they should be pulled and inspected. Mine were in
near new condition at 500 hours.

[tony roberts]

Mine were just rebuilt 4 hours ago and now I have left mag problems
again - it has dropped 100, 400, and cut out.
My A&E is away so I'm grounded until he gets back


Tony

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE

In article >,
"Dave Stadt" > wrote:

> "tony roberts" > wrote in message
> news:nospam-A30BC4.22543423042005@shawnews...
> > My Slicks gave a problem on left mag drop at 1200 hrs and were repaired.
> > Until the problem, mag maintenance hadn't even occured to me - there's
> > just too many things to be aware of in aircraft ownership - I guess that
> > one just slipped under the radar.
> >
> > Tony
>
> Slick says at 500 hours they should be pulled and inspected. Mine were in
> near new condition at 500 hours.

[[email protected]]

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

[nrp]

Presently I have Slick 4200 (4201 and 4251 as I recall) Series mags on
a Cessna 172M.

The timing to the engine has not changed since the initial new
installation, and remains within specs. They are now at about 900 hrs
since new. This is flat country so I 'm leaving them alone for now.

I've never experienced a rough mag since I quit renting aircraft 1600
hrs ago. I'm now at 1700 hrs TT over 40 years all (well most) with 80
octane or autofuel.

[Jim Burns]

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

[[email protected]]

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

[[email protected]]

On 24 Apr 2005 19:29:31 -0700, "nrp" > wrote:

>Presently I have Slick 4200 (4201 and 4251 as I recall) Series mags on
>a Cessna 172M.
>
>The timing to the engine has not changed since the initial new
>installation, and remains within specs. They are now at about 900 hrs
>since new. This is flat country so I 'm leaving them alone for now.
>
>I've never experienced a rough mag since I quit renting aircraft 1600
>hrs ago. I'm now at 1700 hrs TT over 40 years all (well most) with 80
>octane or autofuel.

My alleged experience is derived from private owner-flown aircraft,
rental/trainer aircraft, corporate-owned/professionally flown
aircraft, and charter aircraft.

Average annual utilization of all these types was around 400 hours a
year-the higher utilization of the last three types pulled down by the
first type.

If you are telling me that noone has has to twist your Slick mags in
900 hours, I believe you-but I will say that this is not the norm in
my experience. In theory, the plastic point "cam" stuck into the split
shaft is supposed to wear at the same rate that the points erode,
keeping the point/gap internal timing relatively unchanged. You're
probably living right, it never seems to quite work out that way for
me.

As I indicated, on company aircraft, we yanked them at 500 for
inspection and pitched them at 1000. We figured it was a small price
to pay to eliminate the "rough mag since I quit renting" problem
you've mentioned. On customer aircraft, internal inspection was
predicated by a couple of small mag-to-engine timing changes or one
large one.

Regards;

TC

[[email protected]]

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

[nrp]

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.