X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from rg4.comporium.net ([208.104.2.24] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTPS id 2386729 for flyrotary@lancaironline.net; Sun, 14 Oct 2007 19:21:26 -0400 Received-SPF: neutral receiver=logan.com; client-ip=208.104.2.24; envelope-from=Jewen@comporium.net Received: from 208-104-81-95.lnhe.2wcm.comporium.net (HELO engineer1) ([208.104.81.95]) by rg4.comporium.net (MOS 3.8.4-GA FastPath queued) with SMTP id AEH13951; Sun, 14 Oct 2007 19:20:47 -0400 (EDT) Message-ID: <001d01c80eb8$beeec6f0$6505a8c0@cooleygroup.local> From: "Joe Ewen" To: "Rotary motors in aircraft" Subject: EC2 20B Injector Power Circuits Date: Sun, 14 Oct 2007 19:20:01 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001A_01C80E97.379A78A0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Junkmail-Status: score=10/70, host=rg4.comporium.net X-Junkmail-SD-Raw: score=unknown, refid=str=0001.0A090202.4712A44F.005D,ss=1,fgs=0, ip=208.104.81.95, so=2007-03-13 10:31:19, dmn=5.4.3/2007-09-06 This is a multi-part message in MIME format. ------=_NextPart_000_001A_01C80E97.379A78A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I have been testing my wiring harness from the EC2. I found a behavior = that I did not expect. The manual drawing (EC2 manual) show a single = injector supply that splits at the Injector primary and secondary = disable switches. On my installation, I have 2 separate feeder = circuits, supply Primary comes from battery 1, and supply Secondary = comes from battery 2. I did this for redundancy. If I had a failure = such as a short to ground in either circuit, its related overload should = trip, but the other circuit should remain active. =20 While testing the injector circuits, I noticed what I would term an = abnormality. With both injector disable switches in the enable = position, I turned on the power for the primary circuit (I have LED = indicators on all circuits that annunciate power present) and the = secondary circuit also showed power present even though the power switch = for the secondary circuit was off. The same is true when the secondary = circuit is engaged and the primary is off. =20 Initially this led me to think I had miss wired something in the = circuit. After checking out the wiring, I found no issues. So I took a = closer look at the wiring diagram in the manual. It turns out the power = was being back feed through the injectors to the opposite circuit. On = the 20B version of the EC2, the injector control lines for each rotors = injectors are junctioned going into the EC2. For example the Rotor 1 = Primary and Secondary control lines are junctioned into a single input = point at the EC2. =20 I can see several situations where this may lead to undesirable = operation. For example, if the Primary circuit had a hard short to = ground, it would take out the primary circuit's overload (CB or Fuse.) = Since the primary and secondary circuits are electrically connected on = the control line, the other circuit would also trip. Another situation = that could occur is a medium to high resistance short. Current would = then flow uncontrolled through the unaffected circuit's injector to the = affected circuit's injector then to the resistance short. This could = keep both injectors on 100%. While this situation is unlikely, it seems = possible. I believe the 13B version uses separate control lines for each injector, = so this in not likely to be an issue on the 13B version. It appears that isolation diodes are needed to prevent these possible = problems. Before making any changes I have to look the circuit over = more closely, as well as a call to Tracy on the next service day. My = question to the group, especially anyone with a 20B, is am I looking at = this wrong? Thanks, Joe ------=_NextPart_000_001A_01C80E97.379A78A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I have been testing my wiring harness = from the=20 EC2.  I found a behavior that I did not expect.  The manual = drawing=20 (EC2 manual) show a single injector supply that splits at the Injector = primary=20 and secondary disable switches.  On my installation, I have 2 = separate=20 feeder circuits, supply Primary comes from battery 1, and supply = Secondary=20 comes from battery 2.  I did this for redundancy.  If I had a = failure=20 such as a short to ground in either circuit, its related overload should = trip,=20 but the other circuit should remain active. 
 
While testing the injector circuits, I = noticed what=20 I would term an abnormality.  With both injector disable switches = in the=20 enable position, I turned on the power for the primary circuit (I have = LED=20 indicators on all circuits that annunciate power present) and the = secondary=20 circuit also showed power present even though the power switch for the = secondary=20 circuit was off.  The same is true when the secondary circuit is = engaged=20 and the primary is off. 
 
Initially this led me to think I had = miss wired=20 something in the circuit.  After checking out the wiring, I found = no=20 issues.  So I took a closer look at the wiring diagram in the = manual. =20 It turns out the power was being back feed through the injectors to the = opposite=20 circuit.  On the 20B version of the EC2, the injector control lines = for=20 each rotors injectors are junctioned going into the EC2.  For = example the=20 Rotor 1 Primary and Secondary control lines are junctioned into a single = input=20 point at the EC2. 
 
I can see several situations where this = may lead to=20 undesirable operation.  For example, if the Primary circuit had a = hard=20 short to ground, it would take out the primary circuit's overload (CB or = Fuse.)  Since the primary and secondary circuits are electrically = connected=20 on the control line, the other circuit would also trip.  Another = situation=20 that could occur is a medium to high resistance short.  Current = would then=20 flow uncontrolled through the unaffected circuit's injector to the = affected=20 circuit's injector then to the resistance short.  This could keep = both=20 injectors on 100%.  While this situation is unlikely, it seems = possible.
 
I believe the 13B version uses = separate=20 control lines for each injector, so this in not likely to be an issue on = the 13B=20 version.
 
It appears that isolation diodes are = needed to=20 prevent these possible problems.  Before making any changes I have = to look=20 the circuit over more closely, as well as a call to Tracy on the next = service=20 day.  My question to the group, especially anyone with a 20B, is am = I=20 looking at this wrong?
 
Thanks,
Joe
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