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Subject: Re: [FlyRotary] Re: Failure of an LS-1 D-580 type ignition coil
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From: Tracy <rwstracy@gmail.com>
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Date: Sat, 10 Mar 2012 08:22:36 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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The other guys pretty much nailed it.   Less burning in the chamber and more=
 burning in the exhaust header.

Tracy

Sent from my iPad

On Mar 9, 2012, at 11:53 PM, Dave <david.staten@gmail.com> wrote:

> On 3/9/2012 10:22 PM, DLOMHEIM@aol.com wrote:
>>=20
>> Tracy wrote:  >As usual, the in-flight symptom was a rise in EGT on the a=
ffected rotor.
>> =20
>> Can someone describe the science behind a "rise in EGT" when we lose a si=
ngle 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 pro=
vide cooler temps of the exhaust stream as it passes the EGT probe.
>> =20
>> Must be missing something very basic here...
>> =20
>> Thanks for any clarity!  :)
>> =20
>> Doug Lomheim
>> RV-9A / 13B FWF
>=20
> The rotor combustion space is long and narrow at TDC. If you ignite the fu=
el air charge in a rotary at tdc from only one end, the flame front progress=
es 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 burnin=
g of the fuel-air charge from opposite ends, and to extract as much power fr=
om the charge as possible before the "power stroke" portion of rotor rotatio=
n uncovers an exhaust port and begins the "exhaust stroke"
>=20
> So.. in an abnormal condition characterized by a single coil failure (out o=
f 4 coils).. the affected plug is dead... and the affected rotor has incompl=
ete and SLOWER burning of the charge than normal. This delayed burning persi=
sts after the exhaust port is uncovered. So instead of exhaust gases (which h=
ave already lost heat to the block) passing by the EGT probe, you have actua=
l 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.=20
>=20
> Make Sense?
> Dave (a lingering former rotorhead)

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<html><body bgcolor="#FFFFFF"><div>The other guys pretty much nailed it. &nbsp; Less burning in the chamber and more burning in the exhaust header.</div><div><br></div><div>Tracy<br><br>Sent from my iPad</div><div><br>On Mar 9, 2012, at 11:53 PM, Dave &lt;<a href="mailto:david.staten@gmail.com">david.staten@gmail.com</a>&gt; wrote:<br><br></div><div></div><blockquote type="cite"><div>
    On 3/9/2012 10:22 PM, <a class="moz-txt-link-abbreviated" href="mailto:DLOMHEIM@aol.com"><a href="mailto:DLOMHEIM@aol.com">DLOMHEIM@aol.com</a></a> wrote:
    <blockquote cite="mid:list-5436018@logan.com" type="cite">
      
      
      <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>
  

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