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Date: Sat, 19 Jan 2013 18:27:23 -0500
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Subject: Re: [LML] RPM on IO550N
From: Charles Brown <browncc1@verizon.net>
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References: <list-6018915@logan.com>

I believe most IO550 tach pickups are from a magneto and that there's no =
other electronic crank position indicator.  The elements common to your =
three glass panels probably are the wire running from a magneto lead and =
some sort of A/D converter. =20

On Jan 18, 2013, at 2:04 PM, Berni Breen wrote:

I just started experiencing widely varying RPM read outs on all 3 of the =
gauges of my Lancair Legacy.  During run up and subsequent take off my =
MFD, PFD and EIS all show correct RPM read outs.  Not until I get into =
cruise and set the prop to 2400 do I see the problem.  I slowly begin to =
see all 3 of the read outs start to show a 2300 to 2600 (or there =
abouts) variance.  All 3 gauges are in sync and agreement on the =
numbers.  In other words, they all 3 read the same thing and the =
variance is very rapid up and down.  Since I have already concluded that =
the prop governor is functioning properly and I do not feel or hear a =
prop pitch change during these occurrences, I am all but 100% sure I =
have some sort of erroneous information being sent to my "glass" and =
therefore erroneous readings.  As such I believe I need to check all of =
the wiring and or "pick ups" between the engine and my MFD, PFD and EIS. =
 My problem is that I am not familiar with any of that.  Can someone =
reading this please help me get started by suggesting where I should =
look for the source of where my equipment gets the RPM information from =
the IO550 (location of pick up)?  Further, any kind of procedure to =
track down where or what my problem might be would be most appreciated.

BTW, my read outs are on my GRT HX MFD and PFD as well as my VP200.  I =
know these units are displaying what they believe to be accurate =
information as everything else is functioning flawlessly.  I removed my =
prop governor, sent it for overhaul and it checked out perfect.

Sent from my iPad
Berni Breen
Bbreen@cableone.net
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