Redundancy

[Ron Van Putte]

There's been a lot of discussion about using two battery packs to 
provide extra capacity and redundancy.  However, as Dean Pappas 
mentioned earlier, most battery packs fail shorted, so they still 
provide energy, albeit at reduced voltage and with limited current.  
However, I have seen many servos fail and their failure mode is usually 
"dead at neutral" or "dead hard over".  Neither of these modes of 
failure is particularly conducive to airplane well being.  Most of us 
use two aileron servos and having two aileron servos saved two 
different airplanes of mine.  One servo failed "dead at neutral" and 
the other "dead hard over".  The first was not a problem.  The second 
was a struggle, but I got it on the ground safely.  After the second 
servo failure on aileron, I started using dual elevator servos on all 
my airplanes.  I haven't had a servo fail on elevator yet, but, if one 
does, I'll have a fighting chance to get the airplane back on the 
ground safely.

Ron Van Putte


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