Received-SPF: pass
 receiver=logan.com; client-ip=209.85.210.180; envelope-from=david.staten@gmail.com
Message-ID: <4F5ADE5D.706@gmail.com>
Date: Fri, 09 Mar 2012 22:53:49 -0600
From: Dave <david.staten@gmail.com>
User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2
MIME-Version: 1.0
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Failure of an LS-1 D-580 type ignition coil
References: <list-5436018@logan.com>
In-Reply-To: <list-5436018@logan.com>
Content-Type: multipart/alternative;
 boundary="------------020606060303080904020404"

This is a multi-part message in MIME format.
--------------020606060303080904020404
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

On 3/9/2012 10:22 PM, DLOMHEIM@aol.com wrote:
> Tracy wrote: >As usual, the in-flight symptom was a rise in EGT on the 
> affected rotor.
> Can someone describe the science behind a "rise in EGT" when we lose a 
> single coil.  I would have expected a drop in EGT due to less thorough 
> burning of the mixture and therefore excess un-burnt fuel which I 
> thought would provide cooler temps of the exhaust stream as it passes 
> the EGT probe.
> Must be missing something very basic here...
> Thanks for any clarity!  :)
> Doug Lomheim
> RV-9A / 13B FWF

The rotor combustion space is long and narrow at TDC. If you ignite the 
fuel air charge in a rotary at tdc from only one end, the flame front 
progresses slowly from one end of the "combustion chamber" to the other. 
Two plugs (and coils) for each rotor are present in order to facilitate 
complete burning of the fuel-air charge from opposite ends, and to 
extract as much power from the charge as possible before the "power 
stroke" portion of rotor rotation uncovers an exhaust port and begins 
the "exhaust stroke"

So.. in an abnormal condition characterized by a single coil failure 
(out of 4 coils).. the affected plug is dead... and the affected rotor 
has incomplete and SLOWER burning of the charge than normal. This 
delayed burning persists after the exhaust port is uncovered. So instead 
of exhaust gases (which have already lost heat to the block) passing by 
the EGT probe, you have actual flame front (from the still burning fuel 
air charge) passing the probe and combustion continues in the tailpipe. 
That explains why EGT on the affected rotor would rise in a rotary with 
dual plugs/coils per rotor. A single dead plug from fouling or other 
causes could also provide the same result.

Make Sense?
Dave (a lingering former rotorhead)

--------------020606060303080904020404
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

<html>
  <head>
    <meta content="text/html; charset=ISO-8859-1"
      http-equiv="Content-Type">
  </head>
  <body bgcolor="#FFFFFF" text="#000000">
    On 3/9/2012 10:22 PM, <a class="moz-txt-link-abbreviated" href="mailto:DLOMHEIM@aol.com">DLOMHEIM@aol.com</a> wrote:
    <blockquote cite="mid:list-5436018@logan.com" type="cite">
      <meta content="text/html; charset=ISO-8859-1"
        http-equiv="Content-Type">
      <meta name="GENERATOR" content="MSHTML 9.00.8112.16441">
      <font id="role_document" color="#000000" face="Arial" size="2">
        <div>Tracy wrote:&nbsp; &gt;As usual, the in-flight symptom was a
          rise in EGT on the affected rotor.</div>
        <div>&nbsp;</div>
        <div>Can someone describe the science behind a "rise in EGT"
          when we lose a single coil.&nbsp; I would have expected a drop in
          EGT due to less thorough burning of the mixture and
          therefore&nbsp;excess un-burnt fuel which I thought would
          provide&nbsp;cooler temps of the exhaust stream as&nbsp;it passes
          the&nbsp;EGT probe.</div>
        <div>&nbsp;</div>
        <div>Must be missing something very basic here...</div>
        <div>&nbsp;</div>
        <div>Thanks for any clarity!&nbsp; :)</div>
        <div>&nbsp;</div>
        <div>Doug Lomheim</div>
        <div>RV-9A / 13B FWF</div>
      </font>
    </blockquote>
    <br>
    The rotor combustion space is long and narrow at TDC. If you ignite
    the fuel air charge in a rotary at tdc from only one end, the flame
    front progresses slowly from one end of the "combustion chamber" to
    the other. Two plugs (and coils) for each rotor are present in order
    to facilitate complete burning of the fuel-air charge from opposite
    ends, and to extract as much power from the charge as possible
    before the "power stroke" portion of rotor rotation uncovers an
    exhaust port and begins the "exhaust stroke"<br>
    <br>
    So.. in an abnormal condition characterized by a single coil failure
    (out of 4 coils).. the affected plug is dead... and the affected
    rotor has incomplete and SLOWER burning of the charge than normal.
    This delayed burning persists after the exhaust port is uncovered.
    So instead of exhaust gases (which have already lost heat to the
    block) passing by the EGT probe, you have actual flame front (from
    the still burning fuel air charge) passing the probe and combustion
    continues in the tailpipe. That explains why EGT on the affected
    rotor would rise in a rotary with dual plugs/coils per rotor. A
    single dead plug from fouling or other causes could also provide the
    same result. <br>
    <br>
    Make Sense?<br>
    Dave (a lingering former rotorhead)<br>
  </body>
</html>

--------------020606060303080904020404--