X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-qy0-f182.google.com ([209.85.221.182] verified) by logan.com (CommuniGate Pro SMTP 5.2.15) with ESMTP id 3781666 for flyrotary@lancaironline.net; Sun, 26 Jul 2009 15:40:57 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.221.182; envelope-from=rwstracy@gmail.com Received: by qyk12 with SMTP id 12so3262891qyk.7 for ; Sun, 26 Jul 2009 12:40:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:date :x-google-sender-auth:message-id:subject:from:to:content-type; bh=jyRpuldfGBFiKfAgfJOhupQP/nw/9W98lSWjLVaWvHU=; b=Z0XOcneILMX3Ccbot0xKzW/wbd7bbG0XLqf+qN5tmCaYCJQvuHSFxcXeNAGDfcguyK mjR3D4BjAhc+SZa7KSicgA5LcGYVchmQUnKxwKuF3DS/tS4fPbdZjuaEzrk7TO/74Ynu KkOTBnrBfZ1u68XP3T6xQuGMPQhugppLihUOQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:date:x-google-sender-auth:message-id:subject :from:to:content-type; b=UTB7HQ06f2anBMc/+QAHf0Q0ghGn9ERfN2h/+8AhLwVEiKysGNCe7WTJbu3r/Cd9fm Xo7W51zzIMmOTnlwp5jidmOYN028gBHE1T8qgnGArFX23blQHxpk2FZiSiUz2+fGGEH/ 91vOiQqYyqyQDlhVPOpuF0OV/HMbX7t0xEXaM= MIME-Version: 1.0 Sender: rwstracy@gmail.com Received: by 10.224.60.149 with SMTP id p21mr5322396qah.10.1248637221253; Sun, 26 Jul 2009 12:40:21 -0700 (PDT) Date: Sun, 26 Jul 2009 15:40:21 -0400 X-Google-Sender-Auth: 7721f8131a366d98 Message-ID: <1b4b137c0907261240y63d608e0xc75d28a79472ada6@mail.gmail.com> Subject: Re: [FlyRotary] I Hate 100LL From: Tracy Crook To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015175cb91406b508046fa1020a --0015175cb91406b508046fa1020a Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable It all sounds consistent with SAG Steve. I burned 1 full load of 100LL (~30 gal) on the way back from Texas (I think this was the first time since switching to Iridium spark plugs) and by the time I got home the engine was starting to show the onset of SAG. The plugs had over 300 hours on them using auto fuel prior to this with no hint of a problem. I can't wait for 100LL to disappear. Tracy On Mon, Jul 6, 2009 at 6:48 PM, sboese wrote: > Some of you may remember that I returned home from the Rotorfest at the > end of May to find the internal baffle of my muffler broken. I theorized > that the broken part may have partially blocked the outlet and caused a > power drop compared to what I should have been producing. Pictures of th= e > broken parts and repair were posted on the list last month. > > > > When the weather and my time off coincided recently, I gave the repaired > muffler a flight test after a ground run to be sure things were working > normally. The flight lasted 9 minutes. The plane was much lighter than > when leaving Texas, but the density altitude was about 9000 ft which is > normal for here. The plane would barely climb, would not accelerate over > 110 kts, and the oil and coolant temperatures were abnormally high. This > was quite similar to the data that I posted last month which was a record= of > the take off and climb upon leaving the Rotorfest. > > > > Since the repair to the muffler was not a fundamental change in design, > blaming the lack of performance on the damaged muffler was probably > incorrect. So what was happening? With the engine shut down and still wa= rm, > turning it over slowly with the prop produced a faint clicking noise in a > regular pattern. All indications were that the noise was coming from > internal to the engine. Compression was fine on all compression strokes > when turning with the prop. I thought that maybe the engine had develope= d > chatter marks in the rotor housings to the extent that the apex seals wou= ld > make the clicking noise when turning slowly while also losing compression > when turning fast enough that the apex seal could not follow the uneven > surface of the housing. Pretty remote possibility, I know, but grasping = at > straws makes one come up with some pretty weird ideas. This was > investigated by removing the exhaust headers and looking into the chamber= s. > No chatter marks were seen. Everything I could check short of a complete > engine teardown seemed to be normal. > > > > To make a long story short, replacing the spark plugs brought things back > to normal as demonstrated by a subsequent flight test. So the data poste= d > last month is most likely not a record of operation with increased back > pressure as I had indicated, but rather one of operation with spark plug > SAG. This also is in line with the observation during the trip to the > Rotorfest at one point where I fully opened the throttle for a short time > and observed the RPM to drop off slightly. I was under the impression th= at > when SAG occurs, it is sudden and unmistakable. Apparently with my syste= m, > at least, it can be somewhat insidious. The SAGGED take off when leaving > from Texas didn=92t seem unusual since I=92m used to the lower power leve= ls > produced at the high density altitudes here. The trip around the pattern > after SAG developing gradually during time right around liftoff was > memorable. > > > > Oh, the clicking noise? It turned out to be due to the slight lash in th= e > crank angle sensor gear when a sensor point was magnetically pulled into > alignment with the pickup. Being a little more hard of hearing could hav= e > saved me a lot of work. > > > > Steve Boese > > > > > > > --0015175cb91406b508046fa1020a Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable It all sounds consistent with SAG Steve.=A0=A0 I burned 1 full load of 100L= L (~30 gal) on the way back from Texas (I think this was the first time sin= ce switching to Iridium spark plugs) and by the time I got home the engine = was starting to show the onset of SAG.=A0 The plugs had over 300 hours on t= hem using auto fuel prior to this with no hint of a problem.=A0

I can't wait for 100LL to disappear.=A0

Tracy

On Mon, Jul 6, 2009 at 6:48 PM, sboese <sboese@uwyo.edu> w= rote:

Some of you may remember that I returned home from the Rotorfe= st at the end of May to find the internal baffle of my muffler broken.=A0 I theorized that the broken part may have partially blocked the outlet and ca= used a power drop compared to what I should have been producing.=A0 Pictures of the broken parts and repair were posted on the list last month.

=A0

When the weather and my time off coincided recently, I gave the repaired muffler a flight test after a ground run to be sure things wer= e working normally.=A0 The flight lasted 9 minutes.=A0 The plane was much lighter than when leaving Texas, but the density altitude was about 9000 ft which is normal for here.=A0 The plane would barely climb, would not accelerate over 110 kts, and the oil and coolant temperatures were abnormal= ly high.=A0 This was quite similar to the data that I posted last month which = was a record of the take off and climb upon leaving the Rotorfest.

=A0

Since the repair to the muffler was not a fundamental change in design, blaming the lack of performance on the damaged muffler was proba= bly incorrect. So what was happening?=A0 With the engine shut down and still warm, turning it over slowly with the prop produced a faint clicking noise = in a regular pattern.=A0 All indications were that the noise was coming from internal to the engine.=A0 Compression was fine on all compression strokes when turning with the prop.=A0 I thought that maybe the engine had develope= d chatter marks in the rotor housings to the extent that the apex seals would make the clicking noise when turning slowly while also losing compression w= hen turning fast enough that the apex seal could not follow the uneven surface = of the housing.=A0 Pretty remote possibility, I know, but grasping at straws makes one come up with some pretty weird ideas.=A0 This was investigated by removing the exhaust headers and looking into the chambers.=A0 No chatter marks were seen.=A0 Everything I could check short of a complete engine teardown seemed to be normal.=A0

=A0

To make a long story short, replacing the spark plugs brought things back to normal as demonstrated by a subsequent flight test.= =A0 So the data posted last month is most likely not a record of operation with increased back pressure as I had indicated, but rather one of operation wit= h spark plug SAG.=A0 This also is in line with the observation during the tri= p to the Rotorfest at one point where I fully opened the throttle for a short time and observed the RPM to drop off slightly.=A0 I was under the impression that when SAG occurs, it is sudden and unmistakable.=A0 Apparently with my system, at least, it can be somewhat insidious.=A0 The S= AGGED take off when leaving from Texas didn=92t seem unusual since I=92m used to the lower power levels produced at the high density altitudes here.=A0 T= he trip around the pattern after SAG developing gradually during time right ar= ound liftoff was memorable.

=A0

Oh, the clicking noise?=A0 It turned out to be due to the slight lash in the crank angle sensor gear when a sensor point was magnetic= ally pulled into alignment with the pickup.=A0 Being a little more hard of hearing could have saved me a lot of work.

=A0

Steve Boese

=A0 =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0

=A0

=A0


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