X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 2 [X] Return-Path: Received: from ms-smtp-02.southeast.rr.com ([24.25.9.101] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2055331 for flyrotary@lancaironline.net; Sun, 20 May 2007 14:21:49 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-02.southeast.rr.com (8.13.6/8.13.6) with SMTP id l4KIL03k024399 for ; Sun, 20 May 2007 14:21:00 -0400 (EDT) Message-ID: <000b01c79b0b$de963540$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: LONG! Marginal? Marginal? was Marginal Cooling contributes to Crash. Date: Sun, 20 May 2007 14:22:47 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0008_01C79AEA.57122460" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0008_01C79AEA.57122460 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Al, I certainly understand your postion. I have made all of my (many) = embarrasing moments public so indeed someone has the opportunity not to = make my mistake. Might save an engine, and aircraft and more = importantly - a life.=20 While I may not always agree with your viewpoint or at least to the = same degree, that does not mean I am not safey concious, nor do I advise = others to ignore safety. Every adult has to made decisions for = themselves - yes, there are plenty of people who are willing to made = that decision for you. In some cases, they are experts in the area and = know what they are taking about and in other cases ... well, they = basically have an opinion or have some experience they believe provides = some insight into the situation. However, I still maintain that if we are going to categorize systems = as such then there are (should be) specific perameters and specific = values to be assoicated with a system that mades the dividing line = between the marginal and the "safe" system. And I would like to be = made aware of them. My personal view is that almost any system can be operated in some = condition or set of circumstances can would cause its effectiveness to = be described as marginal. =20 Futhermore, I have seen examples of people fixing "marginal" areas to = the determent of other areas. =20 As you know, sometimes folks are inclinded to "beef" up the area of an = airframe because they believe it to be "marginal" for some reason. Of = course, what they frequently do with this "beefing" up is simply to = transfer that load (or portion of it) to some other area of the airframe = that was Not designed to carry such a load. So here a change was made = because for some reason an indivdual decided it needed beefing up - did = he do this because his structural engineering background suggested it or = because he "thought" it was marginal?=20 Again, without specifics, marginal is simply not a very useful term in = my book. But while I have studied and used FMEA approaches (although = not to the extent you apparently have), they are only as good as the = data and understanding that is applied in using them. Marginal is one = of those "emotional" words which simply does not a convey very = operative information - in my opinion. Lets take a look at my system. On my temperature gages, I checked (on my = last flight) and found that my "RED bar" for or is 210F oil and 220F = for coolant temps. Now my opinion is that of the two that oil = temperatue is the more critical - mainly because its the internal heat = removal mechanism of the rotors. I have reached 200F on the oil and = 220F on coolant for those hot (90F+) days. The vast majority of the = time the oil never exceeds 195F. The nomral coolant temps on take off = on those hot days is 210F. Now the question is what makes those "Red = Bar" temperatures magic. =20 If I put the "Red Bars" at 220 and 240F and only hit 200 and 210F on = take off would my system now be no longer marginal? Of course, not, = we both know where the red bar is at does not necessarily mean anything = about how close or far from the margin you may be. So what does? =20 There is undoubtedly some heat related conditions as reflected in = oil/coolant temperature limits which if exceeded will unquivocably = cause damage to the rotary. But, What are they? Where can we find = them? and do we understand under what conditions they occur? For what = duration must they exist for damage to occur - instanteous, 30 seconds? = five minutes? The ONLY thing I have ever found on rotary temp limits was that = published by Racing Beat in their early 1980s technical catalog. Even in = there they describe temperature limits with cavets.=20 For instance they give a coolant temp limit of 185F - then they state = that if the temperature increase rises slowly engine damage is not = likely to happen even if their stated limited was exceeded by 15 F (this = brings up up to 200F) on the other hand if the temperature rise was = quick due to a broken hose, lost fan belt, etc, then engine damage is = likely. So In this case there was a 15F difference in the point = engine damage was likely to happen - depending on the conditions. Keep in mind that these were describing the older 13B blocks - changes = have been made in the castings for the housings since then to improve = cooling (mainly due to the addition of turbochargers which considerably = increased the heat they had to get rid of). Do they necessary change any = temp limits - don't know (but I suspect so).=20 Furthermore what kind of damage would exceeding the cooling margins = likely bring. Well, the first item likely to fail experience has shown = is the stock coolant "O" rings around the combustion chambers . The = orginal stock "O" rings had the look and feel of thick rubber bands. = They did not look like they would take much heat abuse (and apparently = did not) and they are what keep the combustion gases and coolant = separated - so would not be too suprising for them to fail first.=20 The rotary racing crowd first took action and started using TES "O" = rings which showed much more resistance to overheating. Now, most of us = no longer use the stock coolant "O" rings at all but instead use the = Teflon Encoated Silicon TES "O" rings with much higher temperature = capability. =20 So does this mean we can safely exceed 200F maybe so, maybe no. My bet = is if the stock O ring was first point of failure then switching "O" = rings moved the temp limit for "O" rings beyond 240F. But, even if I = were correct, we don't know for certain what the next component to fail = might be? Perhaps it fails at 210F. In that case, the 400F coolant "O" = rings don't buy us much 0r perhaps the next failure items is at 230F. If = that were the case the the change of Coolant "O" rings buy us a nicely = increased margin. I simply do not know. =20 Sorry to take up so much windage, but my point is we need to better know = the failure mechanisms and their limits before we can accurately assess = a "marginal" system. If a system repeated operates and exceeds the = "marginal" limits we set and continues to operate without failure mean = the system is extrodinary, the operator is lucky?(don't you just love = that word). 0r does it means the margin assessment limits might be too = low or perhaps that we do not understand the failure mechanism. In any case, Al. My viewpoint is your motivation is right on the money, = couldn't agree more - if I see something I personally feel could cause = damage or particularly harm, I would speak out on it. That I may take = issue with you on some points does not in any way mean I don't = appreaciate and respect your viewpoint. I think such debate does more = to simulate thinking that any dogmatic statement. There is no doubt in = my mind that after such a debate someone, somewhere has the light bulb = come on (sometimes its even mine {:>). By the way, did you have any luck finding clams? Best Regards Ed " In there if memory services me the limits were ------=_NextPart_000_0008_01C79AEA.57122460 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Al,
 
I certainly understand your postion.  I = have made all=20 of my (many) embarrasing moments public so indeed someone has the = opportunity=20 not to make my mistake.  Might save an engine, and aircraft and = more=20 importantly - a life. 
 
 While I may not always agree with your = viewpoint or=20 at least to the same degree, that does not mean I am not safey concious, = nor do=20 I advise others to ignore safety.  Every adult has to made = decisions for=20 themselves - yes, there are plenty of people who are willing to made = that=20 decision for you.  In some cases, they are experts in the area and = know=20 what they are taking about and in other cases ... well, they basically = have an=20 opinion or have some experience they believe provides some insight into = the=20 situation.
 
 However, I still maintain that  if we = are going=20 to categorize systems as such then there are (should be)  specific=20 perameters and specific values to be assoicated with a system that mades = the=20 dividing line between the marginal and the "safe" system.  And = I =20  would like to be made aware of them.
 
My personal view is that almost any system can = be operated=20  in some condition or set of circumstances can would cause its = effectiveness to be described as marginal. 
 
Futhermore, I have seen examples of people = fixing=20 "marginal" areas to the determent of other areas. 
As you know, sometimes folks are inclinded to = "beef" up=20 the area of an airframe because they believe it to be "marginal" for = some=20 reason.  Of course, what they frequently do with this "beefing" up = is=20 simply to transfer that load (or portion of it) to some other area of = the=20 airframe that was Not designed to carry such a load.    = So here a=20 change was made because for some reason an indivdual decided it needed = beefing=20 up - did he do this because his structural engineering background = suggested it=20 or because he "thought" it was marginal? 
 
 Again, without specifics, marginal is = simply not a=20 very useful term  in my book.  But while I have studied = and used=20 FMEA approaches (although not to the extent you apparently have), they = are only=20 as good as the data and understanding  that is applied in using = them.=20 Marginal is one of those "emotional" = words  which=20 simply does not a convey very operative information - in my=20 opinion.
 
Lets take a look at my system. On my = temperature=20 gages, I checked (on my last flight)  and found that my "RED bar" = for=20  or  is 210F oil and 220F for coolant temps.  Now my = opinion=20 is that of the two that oil temperatue is the more critical - mainly = because its=20 the internal heat removal mechanism of the rotors. I have =  reached=20 200F on the oil and 220F on coolant for those hot (90F+)=20 days.  The vast majority of the time the oil never exceeds = 195F. =20 The nomral coolant temps on take off on those hot days is = 210F.  Now=20 the question is what makes those "Red Bar" temperatures=20 magic.  
 
 
If I put the "Red Bars" at 220 and 240F and only = hit 200=20 and 210F on take off would my system now be no longer=20 marginal?      Of course, not, we both know = where the=20 red bar is at does not necessarily mean anything about how close or far = from the=20 margin you may be.  So what does? 
 
There is undoubtedly some heat related = conditions as=20 reflected in oil/coolant  temperature limits which if exceeded will = unquivocably cause damage to the rotary.  But, What are they?  = Where=20 can we find them? and do we understand under what conditions they = occur? =20 For what duration must they exist for damage to occur - instanteous, 30 = seconds?=20 five minutes?
 
The ONLY thing I have ever found on rotary temp = limits was=20 that published by Racing Beat in their early 1980s technical = catalog. Even=20 in there they describe  temperature limits with = cavets. 
 
 For instance they give a=20 coolant temp limit of 185F - then they state that if the = temperature=20 increase  rises slowly engine damage is not likely to happen even = if their=20 stated limited was exceeded by 15 F (this brings up up to 200F) =  on=20 the other hand if the temperature rise was quick due to a broken hose, = lost fan=20 belt, etc, then engine damage is likely.    So In this = case there=20 was a 15F difference in the point engine damage was likely to happen=20 - depending on the conditions.
 
 Keep in mind that these were describing = the older=20 13B blocks - changes have been made in the castings for the housings = since then=20 to improve cooling (mainly due to the addition of turbochargers which=20 considerably increased the heat they had to get rid of). Do=20 they necessary change any temp limits - don't know (but I suspect=20 so). 
 
Furthermore what kind of damage would exceeding = the=20 cooling margins likely bring.  Well, the first item =  likely to=20 fail experience has shown is the stock coolant "O" rings around=20 the combustion chambers .  The orginal stock "O" = rings had=20 the look and feel of thick rubber bands.  They did not = look like=20 they would take much heat abuse (and apparently did not)  and = they are=20 what keep the combustion gases and coolant separated - so would not = be too=20 suprising for them to fail first. 
 
  The rotary racing crowd first took action = and=20 started using TES "O" rings which showed much more resistance to=20 overheating.  Now, most of us no longer use the stock coolant = "O"=20 rings at all but instead use the Teflon Encoated Silicon TES "O" = rings with=20 much higher temperature capability. 
 
So does this mean we can safely exceed 200F = maybe so,=20 maybe no.  My bet is if the stock O ring was first point of = failure=20 then switching "O" rings moved the temp limit for "O" rings beyond=20 240F.  But, even if I were correct, we don't know for certain what=20 the next component to fail might be?  Perhaps it fails at = 210F. =20 In that case, the 400F coolant "O" rings don't buy us much 0r = perhaps the=20 next failure items is at 230F. If that were the case the the change of = Coolant=20 "O" rings buy us a nicely increased margin.  I=20 simply do not know. 
 
Sorry to take up so much windage, but my point = is we need=20 to better know the failure mechanisms and their limits before we can = accurately=20 assess a "marginal" system.  If a system repeated operates and = exceeds the=20 "marginal" limits we set and continues to operate without failure mean = the=20 system is extrodinary, the operator is lucky?(don't you just love=20 that word).   0r does it means the margin assessment = limits might=20 be too low or perhaps that we do not understand the failure=20 mechanism.
 
In any case, Al.  My viewpoint is your = motivation is=20 right on the money, couldn't agree more - if I see something I = personally feel=20 could cause damage or particularly harm, I would speak out on it.  = That I=20 may take issue with you on some points does not in any way mean I don't=20 appreaciate and respect your viewpoint.  I think such debate does = more=20 to simulate thinking that any dogmatic statement.  There is no = doubt=20 in my mind that after such a debate someone, somewhere has the light = bulb come=20 on (sometimes its even mine {:>).
 
By the way, did you have any luck finding=20 clams?
 
Best Regards
 
Ed
 
 
 
 
 
 
 
 
"   In there if memory services me the = limits=20 were
 
 
 
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