Mailing List lml@lancaironline.net Message #45524
From: Michael Newman <mnewman@dragonnorth.com>
Sender: <marv@lancaironline.net>
Subject: Redundancy and Electronic Reliability - Avionics Master
Date: Fri, 28 Dec 2007 21:03:12 -0500
To: <lml@lancaironline.net>
Hidden in the last few posts has been a key insight that I would like to emphasize. It is often the simple things that fail and take out far more than is expected.
 
An example is the brightness resistor in the EFIS system. Nobody ever thought it should be redundant.
 
A example from my personal history involves an avionics master switch in my Bonanza. The system was dirt simple the avionics power was switched by a single 30 amp switch type circuit breaker. (Not even a switch and remote relay as is typical.) What happened was that the case of the breaker cracked and it no longer conducted electricity. All the avionics went dark. Happened in flight. The weather was good VFR and I simply flew home. I solved the problem in the Bonanza by adding a second breaker in parallel with an operational note to turn on only one at a time.
 
How many of us have an avionics master system that if it fails will take out way too much?
 
How about the panel master switch? In my Certified Bonanza there is such a switch that can take down all the electrons. With vacuum gyros this is probably OK.
 
In my IV-P I had such a contactor, it is an all electric airplane. Having been burned once I now have two contactors that operate in parallel. The two panel split rocker switches that control the two alternators control the master contactors independently.
 
How does the Avionics master switch work in your plane? What happens if something simple happens like the control wire breaks.
 

Michael Newman

Dragonnorth Group

319 Dean Rd.
Brookline, MA 02445

Cell: 617 821-4608
Home: 617 566-7975
Fax: 617 566-7975

www.dragonnorth.com

mnewman@dragonnorth.com

 
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