X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.122] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4487671 for flyrotary@lancaironline.net; Thu, 30 Sep 2010 12:43:58 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.122; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=GJSIucnNExcGuI2Ikz3ZPUhf4y9MWjZDuW5FdbHj3UY= c=1 sm=0 a=xwo7iSTAZ7sA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=3oc9M9_CAAAA:8 a=ayC55rCoAAAA:8 a=Ia-xEzejAAAA:8 a=oh5byOk4Mn5IYdv5jPQA:9 a=L9ju1lX90Vucv_hO5xgA:7 a=bYiJDPuzNCtGkDmf66d18ANho5EA:4 a=wPNLvfGTeEIA:10 a=U8Ie8EnqySEA:10 a=EzXvWhQp4_cA:10 a=sHmkrbts4CrFDLtK:21 a=WIG2rY5QTWVpgKre:21 a=pedpZTtsAAAA:8 a=E93lBu2AAAAA:8 a=45SIOQMrsibv-HGtZl0A:9 a=HA-ngVJWRxlBv_KKCOAA:7 a=UFfrO5YsOOWk8E-aF00OePQVYYQA:4 a=eJojReuL3h0A:10 a=hO30gm18fF0A:10 a=MpuOTR30KwMA:10 a=FOUTPhXFUAcA:10 a=zgjei8Deq7QA:10 a=NWVoK91CQyQA:10 a=6vrtJ_y2WA5rykiB:21 a=ZrB6f4YLa88HVZQf:21 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:49185] helo=EdPC) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id FD/F6-07415-92EB4AC4; Thu, 30 Sep 2010 16:43:22 +0000 Message-ID: From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Explantion of SAG was New SAG Theory Discussions of SAG Date: Thu, 30 Sep 2010 12:43:10 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0029_01CB609D.0A1FF6B0" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0029_01CB609D.0A1FF6B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Brian, SAG refers an decrease (or sag) in engine performance - since we found = this sag to be associated with the sparkplug, ergo the SAG =3D = "Sparkplug Attention Getter". This condition generally happens - after = approx 25-30 hr of flying with 100LL (considerably longer with Mogas). = But using stock Mazda plugs you will eventually encounter SAG although = the new expensive Irridium plugs may last longer. The sparkplug appears = to have normal wear but just stops working properly. The first thing I notice is that the drone of the engine changes note - = sure to get your attention. The next thing I notice is the EGT on one = (or both if its gotten bad) will drop several hundred degrees on the = affected rotor. The engine RPM will normally drop around 250-300 rpm - = sure to get your attention. Power is reduced. It starts off with perhaps one time on a flight and has you wondering = whether you have an injector or ignition problem - once you learn to = recognize it - its no longer heart stopping - just distracting and = annoying. OK, it may happen once then go away for awhile. But, the = frequency of the eposodes will increase and the duration will be longer. Normally it happens at WOT - we have discovered that throttling back = will temporarily make it go away (for a while). But, needless to say, = you are most likely to first encounter SAG on take off at WOT, one is = NOT inclined to reduce the throttle during that phase of flight (at = least I'm not). However, It will continue to increase in duration and = frequency until you just don't want to fly you aircraft. =20 Tracy Crook was the first to my knowledge to make the association = between SAG and the sparkplug. The worst case I ever had was on the way to a flyin in Memphis TN when = after refueling at a midway point, I took off on a hot day with a fully = loaded RV-6A. Both rotors went into sag right after lift off. Needless = to say I was griping the seat cushion and trying to decide my next = action - when I noticed I still had 500 fpm climb rate - Heck, I said, = when flying a Cessna 150, I thought I was doing great to get 500 fpm. = So I relaxed and circled the airport climbing at 500 fpm until I got to = a couple of thousand feet. Pulled back on the throttle and got my power = back. Fortunately talked to Tracy at the Flyin and found he had an = extra set of plugs which he contributed to the cause. So I normally get 25-30 hours using mainly 100LL - others using Mogas = get well over 100 hours. So my theory was the lead was fouling the = plugs and until Steve's excellent analysis that was about the best = theory we had to go on. Hope this helps Ed Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com From: bktrub@aol.com=20 Sent: Thursday, September 30, 2010 12:15 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG Ok , since I am incapable of public embarassment, what is SAG other than what = I see in the mirror? Brian =20 -----Original Message----- From: Ed Anderson To: Rotary motors in aircraft Sent: Thu, Sep 30, 2010 8:46 am Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG Thanks for the clarification, Steve However, that raises a new question. If the porosity is even a = significant contributing factor to thermal cycling, I would expect the = same thermal cycling deterioration with Mogas or 100LL - not certain why = it would be different between the two? IF not significantly different, = then that leaves the lead enhanced corrosion as the major culprit - at = least that is the way it appears to me. Agree, regardless of cause - the answer is replace the plugs - however, = if you discover the colder plugs last longer - then that would permit me = to reduce my bushel basket storage of old spark plugs - cleaning (even = if it were possible) does not appear to be a option any longer {:>) Ed Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com From: Steven W. Boese=20 Sent: Thursday, September 30, 2010 11:14 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG Ed, You take good notes. Just a couple of clarifications: The decrease in the thermal = conductivity of the copper core may be the result of thermal cycling = causing development of porosity within the copper. This is independent = of the corrosion going on between the Mn alloy electrode sheath and the = insulator. So there are two essentially independent mechanisms = contributing to the heat range change of the spark plug with age. =20 The development of the porosity within the copper is not particularly = affected by the type of fuel whereas the corrosion between the Mn alloy = sheath and the insulator is accelerated by the use of 100LL. The cure is still to install new spark plugs. =20 I have colder spark plugs from Racing Beat that are recommended for = prolonged use in high RPM high power applications. At best, the colder = plugs will merely delay the onset of SAG but won't prevent it from = happening eventually. It will be some time before the results of using = those plugs will be known. Steve Boese =20 -------------------------------------------------------------------------= ------- From: Rotary motors in aircraft [flyrotary@lancaironline.net] On Behalf = Of Ed Anderson [eanderson@carolina.rr.com] Sent: Thursday, September 30, 2010 8:46 AM To: Rotary motors in aircraft Subject: [FlyRotary] New SAG Theory Discussions of SAG In a nut shell, Steve's excellent data gathering (how many of use have = access to a scanning electron microscope or spectrum analyzer {:>)) and = analysis indicates a possible alternative reason for SAG other than = fouling.=20 It basically boils down to a theory of pre-ignition based on the = deteorating heat removal capacity of the plug. =20 There is a copper core (the photos showing the two cores) in the center = of the ceramic cone which is responsible for conducting 90% of the heat = away from the center electrode. Based on Steve's' electron microscope = viewing of two cores (one new and one having been used in a 100LL = environment), it appears that the plug using leaded gasoline has = corrosion occurring on the boundary between this copper core and the = surrounding (hot) elements. This layer of corrosion hinders heat = removal from the plug leading to parts of the plug becoming hot enough = to trigger pre-ignition. This SAG tends to happened at high power settings and reducing power = tends to make it go away (for a while). Steve's theory is that the plug = encounters max heat and temperature at high power settings and that = reducing the power permits the plug to cool off enough for the = pre-ignition to go away (for a while). So we now have two theories - one is the fouled plug and one of the = overheated plug causing SAG. Preignition generally leads to detonation = which does not appear to be happening (at least no one is finding the = typical detonation damage to the rotary engine). A possible reason is = the quenching effect of the less than optimum shape of the rotary = combustion space may tend to delay or prevent the onset of detonation = damage that one would expect from continuous preignition caused by a too = hot plug. I believe Steve intends to see if he can find some colder plugs (the = ones that conduct heat better) and see if that extends the time between = SAG. Currently I find that roughly 25-30 hours is about the max I can = get using 100LL before SAG sets in, whereas Tracy and others have well = over 150 hours using unleaded Mogas. So if the colder plugs extend the = time before SAG, I would say that pretty much would suggest Steve's = theory is correct - if Not, then perhaps the fouled Plug theory still = has merit or it could be some other phenomena happening. Steve, my apologies if I did not present your case as well as you could Ed Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com . From: Bill Bradburry=20 Sent: Thursday, September 30, 2010 9:59 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Discussions of SAG I understand that there was a presentation on SAG at the meeting. Can = someone go over the alternative theory with the ones of us that were not = in attendance? It looked like someone had a scanning electron = microscope photo that they were showing! Wow! Are we getting = sophisticated or what!! Was this an explanation of the cause, or ideas = for prevention, both?? Bill B ------=_NextPart_000_0029_01CB609D.0A1FF6B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Brian,
 
SAG refers an  decrease (or sag) = in engine=20 performance - since we found this sag to be associated with the = sparkplug,=20 ergo the SAG =3D  "Sparkplug Attention Getter".  This = condition=20 generally happens  - after approx 25-30 hr of flying with = 100LL=20 (considerably longer with Mogas).  But using stock Mazda plugs =  you=20 will  eventually encounter SAG although the new expensive Irridium = plugs=20 may last longer.  The sparkplug appears to have normal wear but = just stops=20 working properly.
 
The first thing I notice is that the drone of = the engine=20 changes note - sure to get your attention.  The next thing I notice = is the=20 EGT on one (or both if its gotten bad) will drop several hundred degrees = on the=20 affected rotor.  The engine RPM will normally drop around 250-300 = rpm -=20 sure to get your attention.  Power is reduced.
 
It starts off with perhaps one time on a flight = and has=20 you wondering whether you have an injector or ignition problem - once = you learn=20 to recognize it - its no longer heart stopping - just distracting and=20 annoying.  OK, it may happen once then go away for awhile.  = But, the=20 frequency of the eposodes will increase and the duration will be=20 longer.
 
Normally it happens at WOT - we have discovered = that=20 throttling back will temporarily make it go away (for a while).  = But,=20 needless to say, you are most likely to first  encounter SAG on = take off at=20 WOT, one is NOT inclined to reduce the throttle during that phase of = flight (at=20 least I'm not).  However, It will continue to increase in duration = and=20 frequency until you just don't want to fly you aircraft.  =
 
Tracy Crook was the first to my knowledge to = make the=20 association between SAG and the sparkplug.
 
The worst case I ever had was on the way to a = flyin in=20 Memphis TN when after refueling at a midway point, I took off on a hot = day with=20 a fully loaded RV-6A.  Both rotors went into sag right after lift=20 off.  Needless to say I was griping the seat cushion and trying to = decide=20 my next action - when I noticed I still had 500 fpm climb rate - Heck, I = said,=20 when flying a Cessna 150, I thought I was doing great to get 500 = fpm.  So I=20 relaxed and circled the airport climbing at 500 fpm until I got to a = couple of=20 thousand feet.  Pulled back on the throttle and got my power = back. =20 Fortunately talked to Tracy at the Flyin and found he had an extra set = of plugs=20 which he contributed to the cause.
 
So I normally get 25-30 hours using mainly 100LL = - others=20 using Mogas get well over 100 hours.  So my theory was the lead was = fouling=20 the plugs and until Steve's excellent analysis that was about the best = theory we=20 had to go on.
 
Hope this helps
 
Ed
 
Edward L.=20 Anderson
Anderson Electronic Enterprises LLC
305 Reefton=20 Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com

Sent: Thursday, September 30, 2010 12:15 PM
Subject: [FlyRotary] Re: New SAG Theory Discussions of=20 SAG

Ok ,
since I am incapable of public embarassment, what is SAG other than = what I=20 see in the mirror?
 
Brian 



-----Original=20 Message-----
From: Ed Anderson <eanderson@carolina.rr.com&g= t;
To:=20 Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent:=20 Thu, Sep 30, 2010 8:46 am
Subject: [FlyRotary] Re: New SAG Theory = Discussions=20 of SAG

Thanks for the clarification, Steve
 
However, that raises a new question.  = If the=20 porosity is even  a significant contributing factor=20 to thermal cycling, I would expect the same thermal cycling=20 deterioration with Mogas or 100LL - not certain why it would be = different=20 between the two?  IF not significantly different, then that leaves = the lead=20 enhanced corrosion as the major culprit - at least that is the way it = appears to=20 me.
 
Agree, regardless of cause - the answer is = replace the=20 plugs - however, if you discover the colder plugs last longer - then = that would=20 permit me to reduce my bushel basket storage of old spark plugs - = cleaning (even=20 if it were possible) does not appear to be a option any longer=20 {:>)
 
Ed
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com
 
 

Sent: Thursday, September 30, 2010 11:14 AM
Subject: [FlyRotary] Re: New SAG Theory Discussions of=20 SAG

Ed,
 
You take good notes.
 
Just a couple of clarifications:  = The=20 decrease in the thermal conductivity of the copper core may be the = result of=20 thermal cycling causing development of porosity within the = copper. =20 This is independent of the corrosion going on between the Mn alloy=20 electrode sheath and the insulator.  So there are two essentially=20 independent mechanisms contributing to the heat range change of the = spark plug=20 with age. 
 
The development of the porosity within = the copper=20 is not particularly affected by the type of fuel whereas the corrosion = between=20 the Mn alloy sheath and the insulator is accelerated by the use of=20 100LL.
 
The cure is still = to install new=20 spark plugs. 
 
I have colder = spark plugs from=20 Racing Beat that are recommended for prolonged use in high RPM high = power=20 applications.  At best, the colder plugs will merely delay the = onset of SAG=20 but won't prevent it from happening eventually.  It will be = some time=20 before the results of using those plugs will be = known.
 
Steve Boese
 
  
 
From: Rotary motors = in aircraft=20 [flyrotary@lancaironline.net]=20 On Behalf Of Ed Anderson [eanderson@carolina.rr.com]<= BR>Sent:=20 Thursday, September 30, 2010 8:46 AM
To: Rotary motors in=20 aircraft
Subject: [FlyRotary] New SAG Theory Discussions of=20 SAG

In a nut shell, Steve's excellent data gathering = (how many=20 of use have access to a scanning electron microscope or spectrum = analyzer=20 {:>)) and analysis indicates a possible alternative reason for SAG = other than=20 fouling. 
 
 It basically boils down to a theory of = pre-ignition=20 based on the deteorating heat removal capacity of the plug.  =
 
There is a copper core (the photos showing the = two cores)=20 in the center of the ceramic cone which is responsible for conducting = 90% of the=20 heat away from the center electrode.  Based on Steve's' electron = microscope=20 viewing of two cores (one new and one having been used in a 100LL = environment),=20 it appears that the plug using leaded gasoline has corrosion occurring = on the=20 boundary between this copper core and the surrounding (hot) = elements.  This=20 layer of corrosion hinders heat removal from the plug leading to parts = of the=20 plug becoming hot enough to trigger pre-ignition.
 
This SAG tends to happened at high power = settings and=20 reducing power tends to make it go away (for a while).  Steve's = theory is=20 that the plug encounters max heat and temperature at high power settings = and=20 that reducing the power permits the plug to cool off enough for the = pre-ignition=20 to go away (for a while).
 
So we now have two theories - one is the fouled = plug and=20 one of the overheated plug causing SAG.  Preignition generally = leads to=20 detonation which does not appear to be happening (at least no one is = finding the=20 typical detonation damage to the rotary engine).  A possible reason = is the=20 quenching effect of the less than optimum shape of the rotary combustion = space=20 may tend to delay or prevent the onset of detonation damage that one = would=20 expect from continuous preignition caused by a too hot = plug.
 
I believe Steve intends to see if he can find = some colder=20 plugs (the ones that conduct heat better) and see if that extends the = time=20 between SAG.  Currently I find that roughly 25-30 hours is about = the max I=20 can get using 100LL before SAG sets in, whereas Tracy and others have = well over=20 150 hours using unleaded Mogas.  So if the colder plugs extend the = time=20 before SAG, I would say that pretty much would suggest Steve's theory is = correct=20 - if Not, then perhaps the fouled Plug theory still has merit or it = could be=20 some other phenomena happening.
 
Steve, my apologies if I did not present your = case as well=20 as you could
 
Ed
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com
 
.
 
 

Sent: Thursday, September 30, 2010 9:59 AM
Subject: [FlyRotary] Discussions of SAG

I understand = that there=20 was a presentation on SAG at the meeting.  Can someone go over the=20 alternative theory with the ones of us that were not in = attendance?  It=20 looked like someone had a scanning electron microscope photo that they = were=20 showing!  Wow!  Are we getting sophisticated or what!!  = Was this=20 an explanation of the cause, or ideas for prevention, = both??
 
Bill=20 B
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