Sender: <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Fri, 29 Aug 2008 19:15:40 -0400
Message-ID: <redirect-3100521@logan.com>
Received-SPF: pass
 receiver=logan.com; client-ip=198.36.178.142; envelope-from=JJHALLE@stoel.com
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Subject: Mag myth
Thread-Topic: Mag myth
Thread-Index: AckJvmGMcOsQRFI8QZKaeCOFQJIlNAAYRGNU
References: <list-3099395@logan.com>
From: "Halle, John" <JJHALLE@stoel.com>

For more than 40 years, I have been hearing that piston airplanes use =
mags because they keep on ticking no matter what (unlike the other =
options that, under certain unlikely circumstances, could fail.)  =
Specifically, a complete electrical failure, including any available =
backups, would make things get real quiet unless there was a mag or two =
on board.  That's fine as far as it goes but it ignores a number of =
unfortunate facts such as:
=20
Mags have multiple moving parts that wear over time.
Mags tend to arc at altitude, accelerating wear.
Mags (at least the ones I have been using) are built by Unison.
=20
When I first flew my Legacy, I put in LASAR mags.  They never worked =
right (i.e. never performed better with the LASAR system on than with it =
off.)  In the process of trying to figure out why, after about 300 hrs, =
I pulled both mags and sent them in to Unison.  Their inspection =
revealed that both were shot (nothing to do with LASAR, they were just =
shot) so they threw them out and invited me to buy two more at a small =
discount.  I did but they worked no better so I finally talked Unison =
into exchanging the whole LASAR system for two ordinary mags.  Those =
went on about 200 hrs. ago and, on the way to OSH this year, one of them =
failed in flight.  I had that one replaced (at my expense) and had the =
other inspected.  The inspection revealed a number of worn parts (making =
me feel real good about surviving the failure of the other one) which =
were replaced.  So that's seven mags (plus some parts) in just over 500 =
hrs., all but two paid for by YT and one 60 mile course reversal in =
complete reliance on what was left of one remaining functioning mag.
=20
But wait --- there's more!
=20
My partner in the failed mag adventure just brought to my attention a =
mandatory service bulletin issued by Unison the general point of which =
is that the carbon brush is wearing prematurely in the field.  A decent =
company might offer to replace the brushes (or whatever is causing them =
to wear prematurely) but not Unison.  What they have come up with is =
that any mags that are recently installed or in which certain parts have =
recently been installed, have to be inspected after five hours and then =
twice or three times more in the next 50 (depending on how much time was =
on them when the five hour inspection was made.)  Since the bulletin =
applies to both my mags (one because it is new and the other because of =
the new parts) that means pulling, inspecting, reinstalling and retiming =
both mags every couple weeks or so for a while.  Since those are things =
I don't do myself (having no particular death wish) the cost is likely =
to be considerable, to say nothing of the annoyance.
=20
And finally (except for the Ginsu kinves):
=20
Apparently a friend of mine got one of these bad brush jobs in a brand =
new mag that he installed in his RV-10.  The brush did not take long to =
fail.  In fact, it began failing on climbout on his first flight, making =
the whole experience even more memorable than it would otherwise have =
been.  In subsequent runups, it got worse and worse so they just shut =
down and pulled the mag.
=20
Here's the good news:  Unison is happy to replace the bad mag.
=20
Here's the bad news:  The process they have for doing so is more complex =
than the tax code and takes an average of eight weeks.  (As Dave Barry =
would say, I swear I am not making this up.)
=20
Needless to say, my friend is now several hundred dollars poorer but is =
flying his airplane.
=20
Since I have been flying my airplane, I have had to replace:
=20
the electric fuel pump once;
the vacuum pump once; and
mags five times.
=20
The mags are by orders of magnitude the least reliable component in my =
airplane.  Don't take my word for it -- just take a look at Unison =
Service Bulletin SB3-08.  It's pretty obvious from that how much faith =
Unison has in them.
=20
As soon as the 6-cylinder P-MAG is available, I am going to get a =
reliable ignition system.
=20
=20