From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: [LML] Re: Lancair 320/360 Gear Relay Failure
To: lml
Date: Fri, 19 Aug 2005 00:06:07 -0400
Message-ID: <web-674392@logan.com>
In-Reply-To: <bf.5dbd6b49.3036a2a0@aol.com>
References: <bf.5dbd6b49.3036a2a0@aol.com>
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  From: Sky2high@aol.com
  
  Dan,
  
  I will find the page in the 235 converted to the original 320/360  build
  manual and maybe the page in the POH (if I remember  correctly) that
describes
  this circuit and put them out on LML.
  
  The relays supplied by Lancair are similar to old Ford starter relays meant
  for high current (inductive) loads but intermittent use as opposed to the
  master relay - they have contactor terminals, S+, I and the body which must
be
  grounded because S+ is the positive voltage switched to one side of the coil
  and  the other side is grounded thru the case.  Remember that master relays
  generally have one side of the coil internally wired to the "BAT" marked
  contactor terminal connected to the anode and are activated by  switching 
the
other
  side of the coil to ground by the master power switch.
  
  
  The Legacy wiring is the same in this regard.
  
  
  Additionally, consider this:  The "I" (indicate) terminals on  these relays
  are to be joined and routed to the "pump running" indicator  light.  Many
  people use 18-20 AWG wire for this purpose BUT the tap is  from the 
contactor
that
  carries the motor power - usually thru 8  AWG wire and a 50 Amp breaker.  If
  that indicator wire is ever  shorted, it may burn before it ever triggers 
the
  50 A breaker.  In my  airplane, diodes separate the two relays (no backfeed
to
  the motor alllowed  thru a stuck relay) and an in-line 5 Amp fuse protects
the
  indicator  wire.  At least the last Legacy circuit I saw uses low current
  diodes  to separate the relays and, hopefully, they would blow before the
  indicator  wire burned.
  
  You can only imagine the havoc caused by the overheating and malfunction of
  one of the gear pump relays.  Some of you may remember my story of Arnie 
 and
  I flying our Lancairs to Reno in September, 2001 - a story  entitled "The
Flight of Two Madmen".  He had such a relay failure on  takeoff from Ogden, UT
on
  our way home after 911.  On a Sunday yet, but a  local Napa Parts store had 
a
  replacement relay.  Note that he used to have  his relay circuit going thru 
a
  "MISC" breaker - not now.
  
  Scott Krueger  AKA Grayhawk
  Lancair N92EX IO320 SB 89/96
  Aurora, IL  (KARR)