Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site oakhill.UUCP
Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!genrad!wjh12!talcott!harvard!seismo!ut-sally!oakhill!oscar
From: oscar@oakhill.UUCP (Oscar Strohacker)
Newsgroups: net.aviation
Subject: Re: Wanted:  Cessna Ghostbuster
Message-ID: <252@oakhill.UUCP>
Date: Thu, 29-Nov-84 13:46:03 EST
Article-I.D.: oakhill.252
Posted: Thu Nov 29 13:46:03 1984
Date-Received: Sun, 2-Dec-84 02:43:41 EST
References: <215@ssc-vax.UUCP>
Organization: Motorola Inc. Austin, Tx
Lines: 36


YES, RELAYS DO FAIL
or
CLEAR PROP BEFORE TURNING ON MASTER SWITCH

The original comment was that the power sometimes stays on with the master
off, and the battery discharges. 

I had a 79 Cessna Aerobat 152 in which two relays ("contactors") failed in
a 4 year period after it was new.  Both failed in the on state.  One was a
starter relay and one the master relay.  The parts are similar if not identical.

The first time was during an annual inspection.  I wasn't there to see it,
but apparently the master relay failed inactivating the master switch,
and the A & P created a short while working on the starter.  In the time
it took him to disconnect the battery, it and starter were destroyed.
It cost us > $800 for a new starter, battery, two relays, labor, etc.

The second time, about a year later, I was sitting in the cockpit with the
window open, saying goodbye to my brother standing next to the door.
I flipped on the master to check the fuel guage, and the prop started
cranking just a couple of feet from him!  This time it was a shorted
starter relay.

I sawed open one of the stuck relays with a band saw, and the copper
contacts were sort of pitted and fused as if they had welded themselves
together by sparking when closing.  I inquired about getting the kind
of relays that Cessna uses on its twins, and they were over $200 apiece. 

Cheap transpo, huh?

	oakhill!oscar

	Oscar Strohacker   (Commercial-Inst/ASMEL)
	Motorola MPU Design
	Austin, Texas