X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.4c2) with ESMTP id 4913563 for flyrotary@lancaironline.net; Mon, 21 Mar 2011 10:10:57 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=r4yJ8ACLDmU9N8MfnU6qGSvboKzSN9UnPAeXToqJDNE= c=1 sm=0 a=nbUvcrnsqb4A:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=Ia-xEzejAAAA:8 a=bXqRJZmgQ1NVg94BztYA:9 a=rHd0rbzH1W1G3UmB38MA:7 a=KgUiBPnf6qXwbBh6-jWvGGfknsoA:4 a=wPNLvfGTeEIA:10 a=EzXvWhQp4_cA:10 a=OcHegasKfwlZ-W-N:21 a=ON_wgvXFcru0mjGC:21 a=yMhMjlubAAAA:8 a=UKPAHat8AAAA:8 a=TWITtZyAHszd705Mr5QA:9 a=Mnj8Xj4H-ZGIy0Lu47EA:7 a=IMbuX1AwaTaxRgAaQ89v6ZecFWwA:4 a=7god_763jbgA:10 a=UP6jqP163Ux3bKmW:21 a=-9Ik8WlPy1XAKsZD:21 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:59737] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 5E/6E-09483-E4C578D4; Mon, 21 Mar 2011 14:10:22 +0000 Message-ID: <22FD679E7EDE4F95BBE1AD872A366317@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Wide Band wasRe: [FlyRotary] Re: Forced Landing. Date: Mon, 21 Mar 2011 10:10:20 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0012_01CBE7B0.2FA51740" 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_0012_01CBE7B0.2FA51740 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Bobby, I've looked into wide band O2 sensor a bit. As you know, the = principal difference over the narrow band is that the sensor output = voltage curve is much more linear and extends over a wider range of = voltage (from approx 0.5 - 2.5 vice 0 - 1 for the narrow band). =20 It is not uncommon to have the air/fuel indication vary a bit. I would = not expect each combustion process to be exactly the same as the one = occurring the moment before (but, should be close). So the amount of = oxygen left over in the exhaust gas from each combustion event is = likely to vary (at least a small amount). This in turn would show up as = small variations in the air/fuel ratio. Also RPM might have some = effect, at lower rpm the combustion events are further apart than at = higher rpm. =20 Another possibility is as you mentioned is the possibility that the = sensor is indicating a slight misblance between the two rotors. If that = is the case I would expect the RATE of variation you see to vary with = rpm and be fairly consistent at different air/fuel ratios and rpms. Ah, such fun. Ed From: Bobby J. Hughes=20 Sent: Monday, March 21, 2011 10:18 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Forced Landing.=20 Steve, =20 The wideband may be picking up a small fuel imbalance between the two = rotors. Or is could be perfectly normal for all widebands to jump = around. I would expect an increase in EGT's with a gradual partial = blockage. A high EGT alarm would give some indication. I would also = expect a steady but higher than normal temp with a build in restruction. = But with a sudden blockage at high power? The answer may not be of any = value since only a pressure sensor would tell the pilot to stop trouble = shooting.=20 =20 Bobby -------------------------------------------------------------------------= ------- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On = Behalf Of Steven W. Boese Sent: Sunday, March 20, 2011 8:20 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Forced Landing.=20 =20 Bobby, =20 I have not done any testing with a wideband O2 sensor. Unless the = engine were operating right on a threshold of a large untuned injector = pulse width change (staging is the only thing that comes to mind), it = seems unlikely that the variation in O2 sensor would be associated with = injector delay. =20 Within the limits that were tested, the EGT increased with increased = exhaust back pressure due to partial blockage. The mixture was somewhat = rich and no change in O2 sensor was seen. Lean mixtures were not = investigated at that time. =20 Steve =20 =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On = Behalf Of Bobby J. Hughes Sent: Sunday, March 20, 2011 7:46 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Forced Landing.=20 =20 Steve, =20 Thanks for the offer. Actually I think it would be great if you could = conduct a test. I had thought about a block off plate that could be = pulled into place with a long wire. This would allow a high power test = run with a sudden blockage. It's the only way I can come up with to = create a not so dramatic reinactment. Your test stand would be a better = platform then the airplane. The engine was popping and shaking when the = failure occurred. As best I can remember my wideband O2 was off the = scale lean but I'm not certain. Speaking of wideband O2's. My wideband = has always jumping around a few 10ths or more. My EM3 get's a narrowband = output from the wideband. The EM3's mixture bar appears stable. Could = the wideband be seeing a injector bounce associated with the injector = delay? As an example when leaned for cruise, say 13.2 it's often = switching rapidally between 13.1 and 13.3. At this point the engine = seems reasonable smooth. The larger the bounce the less smooth the = engine becomes. Have you done any of your testing with a wideband?=20 =20 Bobby =20 ------=_NextPart_000_0012_01CBE7B0.2FA51740 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Bobby, I've looked into wide band O2 sensor a = bit. =20 As you know, the principal difference over the narrow band is that the = sensor=20 output voltage curve is much more linear and extends over a wider range = of=20 voltage (from approx 0.5 - 2.5 vice 0 - 1 for the narrow band). =20
 
It is not uncommon to have the air/fuel = indication vary a=20 bit.  I would not expect each combustion process to be exactly the = same as=20 the one occurring the moment before (but, should be close).  So the = amount=20 of oxygen left over in the exhaust gas  from each combustion event = is=20 likely to vary (at least a small amount).  This in turn would show = up as=20 small variations in the air/fuel ratio.  Also RPM might have some = effect,=20 at lower rpm the combustion events are further apart than at higher = rpm. =20
 
Another possibility is as you mentioned is the = possibility=20 that the sensor is indicating a slight misblance between the two = rotors. =20 If that is the case I would expect the RATE of variation you see to vary = with=20 rpm and be fairly consistent at different air/fuel ratios and = rpms.
 
Ah, such fun.
 
Ed

Sent: Monday, March 21, 2011 10:18 AM
Subject: [FlyRotary] Re: Forced Landing.

Steve,

 

The wideband may be = picking up a=20 small fuel imbalance between the two rotors. Or is could be perfectly = normal for=20 all widebands to jump around. I would expect an increase in EGT=92s with = a gradual=20 partial blockage. A high EGT alarm would give some indication.  I = would=20 also expect a steady but higher than normal temp with a build in = restruction.=20 But with a sudden blockage at high power? The answer may not be of any = value=20 since only a pressure sensor would tell the pilot to stop trouble = shooting.=20

 

Bobby

From:=20 Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On=20 Behalf Of Steven W. Boese
Sent: Sunday, March 20, 2011 8:20 = PM
To: = Rotary motors in aircraft
Subject: [FlyRotary] Re: Forced = Landing.=20

 

Bobby,

 

I have not = done any=20 testing with a wideband O2 sensor.  Unless the engine were = operating right=20 on a threshold of a large untuned injector pulse width change (staging = is the=20 only thing that comes to mind), it seems unlikely that the variation in = O2=20 sensor would be associated with injector = delay.

 

Within the = limits that=20 were tested, the EGT increased with increased exhaust back pressure due = to=20 partial blockage.  The mixture was somewhat rich and no change in = O2 sensor=20 was seen.  Lean mixtures were not investigated at that=20 time.

 

Steve

 

 

From:=20 Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On=20 Behalf Of Bobby J.=20 Hughes
Sent:=20 Sunday, March 20, 2011 7:46 PM
To: Rotary motors=20 in aircraft
Subject: [FlyRotary] Re: Forced = Landing.=20

 

 Steve,

 

Thanks for the offer. Actually I = think it=20 would be great if you could conduct a test. I had thought about a block = off=20 plate that could be pulled into place with a long  wire. This would = allow a=20 high power test run with a sudden blockage. It=92s the only way I can = come up with=20 to create a not so dramatic reinactment. Your test stand would be a = better=20 platform then the airplane. The engine was popping and shaking when the = failure=20 occurred. As best I can remember my wideband O2 was off the scale lean = but I=92m=20 not certain. Speaking of wideband O2=92s. My wideband has always jumping = around a=20 few 10ths or more. My EM3 get=92s a narrowband output from the wideband. = The EM3=92s=20 mixture bar appears stable. Could the wideband be seeing a injector = bounce=20 associated with the injector delay? As an example when leaned for = cruise, say=20 13.2 it=92s often switching rapidally between 13.1 and 13.3. At this = point the=20 engine seems reasonable smooth. The larger the bounce the less smooth = the engine=20 becomes. Have you done any of your testing with a wideband?=20

 

Bobby

 

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