X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from web180215.mail.gq1.yahoo.com ([67.195.13.175] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3578211 for flyrotary@lancaironline.net; Sun, 12 Apr 2009 12:46:54 -0400 Received-SPF: neutral receiver=logan.com; client-ip=67.195.13.175; envelope-from=ceengland@bellsouth.net Received: (qmail 44760 invoked by uid 60001); 12 Apr 2009 16:46:16 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bellsouth.net; s=s1024; t=1239554776; bh=ghm0K1Gt2ongumNG/wxuOhgU1vHIcHVf8RalaaVlTzk=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=2iZjUAXjCPqF271ozq8Nn0uddPJF3pFCWghNFXxCbXpyl0ncxAQT59fI5/OHDr+BBY0Uop33W3YEfCj8Gb6TR0Bu86KKK9Lo5rnSuUU2VIaRVwTR+lUzjs7xL3zm+FXoIuWJFXMMHAlItIKcK1yI/wRC/tf3e9ErrIjtPKpcKuM= DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=bellsouth.net; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=2sCIfIFE5jJlzu4dCfGfmmX2V1cHV9xvu7n7HbZl2R7oXabTTuA96rkuB15f414/NU1cRF9/zSuc9aHRMNXMbW9BdKMvx26giDMftbZbN93Sqr0lwzKb64el2I7i/DczoSBTO4Ly59xPmtguLIbFnjfcCTtKWFydtNTu8+qNNao=; Message-ID: <678396.43847.qm@web180215.mail.gq1.yahoo.com> X-YMail-OSG: _abbWe8VM1k9fmz_C2K0DQ9oF7tORKSlP3NwrzaORDpU7otVwjz0BwFvYu3bwUko7r2tBlgOzxGiNFSXwzr4gpIl01r2zlkv4fKFbeBBVxN9UGstGmvuB_GtLACNC_jiOeQ45.Bv1ZYf9DsWya.ovggFIKG5IeeWFPPfONm5Gn31kY7FFPFwJr4owxuPG8jJ6FoyajSd_B506.Dj1VqB04C7jMXyuucGGLnuoJ0GydeTxpwZWwW0OYLI3W64_3kiiXeldXusA1tUKc1KRjOINKu3XGxaistKqfBoNhm0tw-- Received: from [70.151.69.1] by web180215.mail.gq1.yahoo.com via HTTP; Sun, 12 Apr 2009 09:46:16 PDT X-Mailer: YahooMailRC/1277.35 YahooMailWebService/0.7.289.1 References: Date: Sun, 12 Apr 2009 09:46:16 -0700 (PDT) From: Charlie England Subject: Re: [FlyRotary] Re: forced landings To: Rotary motors in aircraft In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-621569458-1239554776=:43847" --0-621569458-1239554776=:43847 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable I think that it's just as important to understand the real cause of the fai= lure. In the case of the plastic fuel flow sensor, it's highly unlikely tha= t use of the plastic sensor caused the failure; it was the use of plastic i= n the wrong area without any protection. The homebuilder's knee-jerk reacti= on is to say 'no plastic sensors because that one melted', even though ther= e are tens of thousands of the same sensor in use in boating, a much more s= evere environment.=0A=0AKind of like the canard builder who tried to put fu= el in a wing built with fuel-soluble foam. Obviously, it failed, but only b= ecause of the wrong application of products, not the products themselves.= =0A=0ACharlie=0A=0A=0A=0A=0A________________________________=0AFrom: al wic= k =0ATo: Rotary motors in aircraft =0ASent: Sunday, April 12, 2009 10:13:00 AM=0ASubject: [FlyRotary] Re= : forced landings=0A=0A=0AAbsolutely excellent Mark. I'd encourage you to g= et the year the incident occured too. That will be your proof of reduced ri= sk from things like this newsgroup. =0AAvoid the black and white approach: = forced landing or not forced. Because all things are shades of grey. Instea= d rate the severity. So it's a 10 if the guy had to glide, it's a 1 if he d= id precautionary landing. If you also explain what happened, then a reader = can easily tell you were objective in your rating. =0AThe final piece is ab= out how many flight hours, first flights there were. Each year there are mo= re engines flying, so way more likely you will hear of incident. A wild ass= ed guess is ok, if you just base the guess on some facts. For example, you = could check faa database and find 100 planes registered with rotary engine = in 2005. You can guess that equals 70 hours each. Even though it's a wild a= ssed guess, it will still be excellent predictor of change over time. Each = year you have the same "error". So your numbers WILL reflect improvement.= =0AMore important than anything. If you can force your self to say: "That s= ame failure will happen to me". Particularly if you can look at "contributi= ng factors". Then you can dramatically reduce personal risk. Good example: = We had that guy that installed plastic fuel flow sensor in fuel line. It me= lted, he died. Tracy just reported hot exhaust caused fuel to boil out of c= arb. These have the same root cause. You don't want to say:" I have efi, ca= n't happen to me". You want to say:" I expect heat will cause a failure. I'= ll put a thin ss shield here, with a bit of fibrefax glued to back. So if m= uffler fails, it won't affect....."=0AEvery forced landing had 10 little in= cidents in the past that preceded it. Your risk isn't some new cause. It's = 1 of those 10 incidents that you rationalized away, instead of saying:" tha= t will happen to me too."=0AGood stuff.=0A=0A-al wick=0ACozy IV with 3.0 li= ter Subaru=0A230+ hrs tt from Portland, Oregon=0A=0A---------- Original Mes= sage ----------=0AFrom: Mark Steitle =0ATo: "Rotary mot= ors in aircraft" =0ASubject: [FlyRotary] Re: G= ary Casey was [FlyRotary] Re: Rotary Engines=0ADate: Sun, 12 Apr 2009 06:45= :24 -0500=0A=0AMike, =0A=0AHas anyone ever tried to document the rotary inc= idents resulting in a forced landing?=0A=0AHere's what I recall from memory= , so it likely is missing a few;=0A =0A 3 forced landings due to rupture= d oil coolers =0A 1 forced landing due to apex seal coming out of its sl= ot (rotor out of spec)=0A 1 forced landing due to improper assembly of e= ngine (seal wedged between rotor & side housing)=0A 1 forced landing on = highway due to catastrophic overheating of engine=0A 2 forced landings (= one fatal) due to probable fuel system design flaw =0A 1 forced landing= on highway due to ingestion of FOD. =0A=0AThere were a few others, such a= s turbo failures which allowed for continued operation at reduced power, so= we may or may not wish to include those here. =0A=0AWhile a number of the= se incidents date back quite a few years, and we have made excellent progre= ss, it says to me that we still have room for improvement in the peripheral= department. The good news is that out of all of the incidents listed abov= e, none of them were caused by a true engine failure. That's where the rot= ary has really earned my respect as a viable a/c engine.=0A=0APay attention= to the details! =0A=0AMark S. =0A=0A=0A=0AOn Sat, Apr 11, 2009 at 9:22 PM,= Mike Wills wrote:=0A=0AThis has been an interesting thr= ead. In the end, it doesnt really matter how many "major" parts you have - = even a minor failure can bring you down. While I believe the basic rotary e= ngine itself is more fault tolerant than a recip, the peripherals used in t= he typical rotary install are a lot more complex than a typical recip insta= ll. Since we rotary fliers dont have the benefit of 70 years worth of exper= ience flying behind the typical LyCon farm implement I think overall our od= ds are considerably worse. Comes down to how well an individual engineer's = his installation and there is a tremendous amount of variation here.=0A =0A= The dependence on electronics in the typical rotary install is a good exam= ple. I may be a little sensitive to this issue since I've been trying to fi= nd an intermittent glitch (2 times in 22 hours of engine testing).=0A Mike = Wills=0ARV-4 N144MW =0A----- Original Message ----- =0AFrom: Ed Anderson = =0ATo: Rotary motors in aircraft =0ASent: Saturday, April 11, 2009 7:31 AM= =0ASubject: [FlyRotary] Gary Casey was [FlyRotary] Re: Rotary Engines=0A=0A= Good analysis and logic, Gary.=0A =0AYou=E2=80=99d make a good addition to = the =E2=80=9Crotary community=E2=80=9D. I have noticed over the 10 years I= have been flying my rotary powered RV-6A that the problems have decreased = considerably, the success rate and completion rate has gone up and first fl= ights are now occurring without significant problems =E2=80=93 even cooling= is OK {:>). I believe most of this improvement can be attributed to folks= sharing their knowledge, problems and solutions with others - such as on t= his list. =0A =0AI know that fewer parts count is often touted as one of t= he rotary benefit =E2=80=93 and while it is true that the part count is low= er, the most significant thing (in my opinion) is not only does the lower p= art count help reliability (if it is not there =E2=80=93 it can not break),= but if you look a the design of the eccentric shaft (for example) you noti= ce the absence of the jogs in a typical crankshaft and their stress points.= The thing is over 3=E2=80=9D in diameter at some points and does not have= the same inertia loads born by a piston crankshaft. The parts that are th= ere are of very robust design. Finally, the rotary is (I believe) more tol= erant of damage and tends to fail =E2=80=9Cgradually and gracefully=E2=80= =9D, it can take a licking and keep on ticking as the old saying goes. Onl= y extended time and numbers will provide the true MTBF for the rotary, but = I believe it looks very promising.=0A =0AFailure of rotary engines are extr= emely rare, but unfortunately, as with many alternative engine installation= s, auxiliary subsystems such as fuel and ignition frequently being one-off = designs have been the cause of most failures =E2=80=93 with probably fuel t= he prime culprit. The good news is that for some platforms (such as the RV= s) we have pretty much established what will make an installation successfu= l. The Canard crowd is fast approaching that status with their somewhat mo= re challenging cooling requirements being over come.=0A =0A Having lost a = rotor during flight due to putting in high compression rotors with worn ape= x seal slots worn beyond specs (found this out later =E2=80=93 my fault for= not being aware of this spec limit and checking it) which led to apex seal= failure and consequence lost of most of the power from one rotor, I was st= ill able to maintain 6500 MSL at WOT and fuel mixture knob to full rich =E2= =80=93 flowing 14.5 GPH =E2=80=93 a lot of it undoubtedly being blown thro= ugh the disabled rotor. Flew it back 60 miles to a suitable runway and mad= e a non-eventful landing. There was a small increase in vibration due to = the power strokes no longer being balanced, but nothing bad and you could s= till read the needles on the gauges. Other folks have had FOD damage to a = rotor and also make it to a safe landing. Two folks lost cooling (one loss= of coolant fluid , one lost of water pump) and while they did cook the eng= ines, both made it back to a safe landing. So all things considered, I think the rotary continues to show that if the installation is designed = properly, it makes a very viable and reliable aircraft power plant.=0A =0AF= ailure of rotary engines in aircraft are extremely rare, but unfortunately,= as with many alternative engine installations, auxiliary subsystems such a= s fuel and ignition frequently being one-off designs - have been the cause = of most failures. The good news is that for some platforms (such as the RV= s) we have pretty much established what will make an installation successfu= l. The Canard crowd is fast approaching that status with their somewhat mo= re challenging cooling requirements being over come.=0A =0AMy rotary instal= lation cost me $6500 back in 1996, the primary cost being a rebuilt engine = $2000 and the PSRU $2900. I have since purchased a 1991 turbo block engine= from Japan for $900 and rebuilt it myself for another $2200. My radiators= (GM evaporator cores) cost $5.00 from the junk yard and another $50.00 eac= h for having the bungs welded on. So depending on how much you buy and how= much you build the price can vary considerably. Today, I would say it wou= ld take a minimum of around $8000 and more nominally around $10000 for a co= mplete rotary installation in an RV =E2=80=93 some folks could do it for le= ss, some for more.=0A =0ABut, regardless of the technical merit (or not) in= someone=E2=80=99s mind, the crucial thing (in my opinion) is you need to a= ddress two personal factors:=0A =0A1. What is your risk tolerance? It doe= sn=E2=80=99t really matter how sexy some =E2=80=9Cexotic=E2=80=9D engine in= stallation may seem =E2=80=93 if you are not comfortable flying behind (or = in front) of it, then it certainly does not makes sense to go that route. = After all, this is supposed to have an element of fun and enjoyment to it.= =0A =0A2. What is your knowledge, experience and background (and you don= =E2=80=99t have to be an engineer) and do you feel comfortable with the lev= el of involvement needed.=0A =0ASo hope you continue to contribute to expan= ding our knowledge and understanding of the rotary in its application to po= wer plant for aircraft.=0A =0A =0ABest Regards=0A =0AEd=0A =0A =0AEd Anders= on=0ARv-6A N494BW Rotary Powered=0AMatthews, NC=0Aeanderson@carolina.rr.com= =0Ahttp://www.andersonee.com=0Ahttp://www.dmack.net/mazda/index.html=0Ahttp= ://www.flyrotary.com/=0Ahttp://members.cox.net/rogersda/rotary/configs.htm#= N494BW=0Ahttp://www.rotaryaviation.com/Rotorhead%20Truth.htm=0A=0A_________= _______________________=0A =0AFrom:Rotary motors in aircraft [mailto:flyrot= ary@lancaironline.net] On Behalf Of Gary Casey=0ASent: Saturday, April 11, = 2009 8:36 AM=0ATo: Rotary motors in aircraft=0ASubject: [FlyRotary] Re: Rot= ary Engines=0A =0AJust to add a few more comments and answers to the severa= l excellent comments posted:=0A =0AHow many parts does it take to make a ro= tary rotate? Well, "parts aren't parts" in this case. Mark was right in t= hat there are maybe 4 "major" components, but you have to define major. A = piston engine certainly has far more major parts. Is a valve a "major" par= t? I think so. Is a rotor corner button a major part? Not sure, but prob= ably not. Is each planet gear in the PSRU a major part? I say yes, and th= e PSRU is an integral part of the rotary engine. As someone correctly poin= ted out, it's not how many parts, but the reliability of the total system t= hat counts. Just looking at the history of the rotary (which, from the imp= lication of another post) it's not that good, but I don't think it has anyt= hing to do with reliability of the concept. It's more to do with the exper= imental nature of the builds and installations. My original point, perhaps= not well expressed is that to say there are just 4 parts is an oversimplif= ication. But let's face it, to put in an engine that has had many thousands of identical predecessors = is less "experimental" than one that hasn't..=0A =0AAre we ES drivers more = conservative? Probably so, since the ES is probably one of the experimenta= ls most similar to production aircraft, and not just because the Columbia (= can't force myself to say Cezzna :-) was a derivative. Therefore, it tends= to attract conservative builders and owners. Not surprising then that alm= ost all ES's have traditional powerplants, with the most excellent exceptio= n of Mark. While there may be more, I know of only two off-airport landing= s caused by engine failures in the ES in almost 20 years of experience. On= e was caused by fuel starvation right after takeoff (fatal) and one was cau= sed by a PSRU failure in an auto engine conversion. So our old-fashioned c= onservative nature has served us pretty well.=0A =0AYes, I was assuming tha= t the rotary had electronic fuel injection and ignition, but that by itself= doesn't change the inherent fuel efficiency of the engine. Direct injecti= on does have a potential to improve BSFC because the fuel charge can be str= atified. It will probably decrease available power, though. I think the b= est rotary will be 5% less efficient than the "best" piston engine(same ref= inements added to each). But I stated that as a simple disadvantage - as M= ark pointed out, it isn't that simple. The rotary already comes configured= to run on auto gas. The piston engine can also be so configured, but the = compression ratio reduction would reduce its BSFC and maybe durability adva= ntage. The total operating cost is certainly significantly less if auto ga= s can always be used to refuel. I assumed in my assessment that it will on= ly be available 50% of the time. The real disadvantage, which I failed to = state, is that the extra fuel required for a given mission might be 5 or 10% higher and that negated the weight advanta= ge, if only for long-range flights.=0A =0AIs the engine less expensive? I = did a thorough analysis of a direct-drive recip auto engine installation an= d my conclusion was that if the auto engine were equivalent in reliability = to the aircraft engine it would likely cost just as much. Is the same true= of the rotary? I'm not sure, but you have to consider the total cost, inc= luding engineering of all the parts in the system, not just the core engine= . I would love to do a rotary installation, but I don't think I could just= ify it by cost reduction.=0A =0AIt wasn't mentioned in the posts, but some = have claimed the rotary is "smoother" than a recip. I at first resisted th= at notion. Sure, any rotary given sufficient counterbalancing, is perfectl= y balanced. A 4-cylinder opposed recip is not - there is a significant sec= ondary couple. The 6-cylinder opposed engine is perfectly balanced, but on= ly for PRIMARY and SECONDARY forces and couples - higher order forces have = never really been analyzed, although they would be very small. And then co= nsider the forces within the engine that have to be resisted by that long, = heavy, but flexible crankshaft. So it isn't the mechanical balance that gi= ves the rotary an advantage. Let's take a look at the the torsional pulsat= ions, comparing the 3-rotor against the 6-cylinder: A 6-cylinder engine ha= s 3 power impulses per rotation, as does the 3-rotor, so they are the same,= right? Wrong. They both incorporate 4 "stroke" cycles, meaning that ther= e separate and sequential intake, compression, power and exhaust events so that is the same for both= . The power event, which is the source of the torque impulse, takes 1/2 of= a crank rotation for the recip. In the rotary the power event requires 1/= 4 of a ROTOR rotation, but the rotor rotates at 1/3 crank rotation - the re= sult is that the power impulse lasts 3/4 of a CRANK rotation, 50% longer th= an in a recip. Therefore, the torsional excitation delivered to the propel= ler, PSRU and to the airframe is significantly less than for a recip. And = if you analyze the actual forces imparted, they go down by the square of th= e rpm. The torsional vibration amplitude goes down by a factor of 4 just b= ecause the rpm of the rotary turns about twice as fast. If you've skipped = to the bottom of the paragraph, as you probably should have :-), yes the ro= tary is "smoother" - a LOT smoother.. (my apologies to rotary purists, for = simplicity I used the word "crankshaft" for both engines)=0A =0ABut just be= cause you can burn auto gas should you? The biggest problems with auto gas= in recip aircraft have nothing to do with the engine, but with the high va= por pressure of the fuel - it is more prone to vapor lock. The fuel system= s of certified aircraft are not particularly well designed with regard to v= apor lock. "Fortunately", rotary engines typically have no mechanical fuel= pump and are forced to rely on electric pumps. Fortunately because the pu= mps can be located at the very bottom of the aircraft and close to the fuel= tanks, making vapor lock much less likely. I would caution any builders t= o consider vapor lock possibilities very seriously, much more so if you int= end to run auto gas. when I was going to do this I planned to put one elec= tric pump in the wing root of each wing, feeding the engine directly(the ch= eck valve in the non-running pump prevents back-feeding). Redundancy was b= y a "crossfeed" line that could connect the tanks together.=0A =0AAnd thanks, Mark for - probably incorrectly - referring to= me as a "good engineer". I'll have to put that in my resume!=0A =0AHave a= good day,=0AGary=0A(do you allow us outsiders in your events? I'll park w= ell away :-)=0A =0A=0A=0A=0A__________ Information from ESET NOD32 Antiviru= s, version of virus signature database 3267 (20080714) __________=0A=0AThe = message was checked by ESET NOD32 Antivirus.=0A=0Ahttp://www.eset.com/=0A --0-621569458-1239554776=:43847 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
I think that it's just as important to understand the rea= l cause of the failure. In the case of the plastic fuel flow sensor, it's h= ighly unlikely that use of the plastic sensor caused the failure; it was th= e use of plastic in the wrong area without any protection. The homebuilder'= s knee-jerk reaction is to say 'no plastic sensors because that one melted'= , even though there are tens of thousands of the same sensor in use in boat= ing, a much more severe environment.

Kind of like the canard builder= who tried to put fuel in a wing built with fuel-soluble foam. Obviously, i= t failed, but only because of the wrong application of products, not the pr= oducts themselves.

Charlie

From: al wick <alwick@juno.com>
To: Rotary motors in aircraft <= flyrotary@lancaironline.net>
Se= nt: Sunday, April 12, 2009 10:13:00 AM
Subject: [FlyRotary] Re: forced landings

=0A

Absolutely excellent Mark. I'd encourage you to get the year t= he incident occured too. That will be your proof of reduced risk from thing= s like this newsgroup.

=0A

Avoid the black and white approach: forced= landing or not forced. Because all things are shades of grey. Instead rate= the severity. So it's a 10 if the guy had to glide, it's a 1 if he di= d precautionary landing. If you also explain what happened, then a reader c= an easily tell you were objective in your rating.

=0A

The final piece= is about how many flight hours, first flights there were. Each year there = are more engines flying, so way more likely you will hear of incident. A wi= ld assed guess is ok, if you just base the guess on some facts. For example= , you could check faa database and find 100 planes registered with rotary e= ngine in 2005. You can guess that equals 70 hours each. Even though it's a = wild assed guess, it will still be excellent predictor of change over time.= Each year you have the same "error". So your numbers WILL reflect improvem= ent.

=0A

More important than anything. If you can force your self to s= ay: "That same failure will happen to me". Particularly if you can look at = "contributing factors". Then you can dramatically reduce personal risk. Goo= d example: We had that guy that installed plastic fuel flow sensor in fuel = line. It melted, he died. Tracy just reported hot exhaust caused fuel to bo= il out of carb. These have the same root cause. You don't want to say:= " I have efi, can't happen to me". You want to say:" I expect heat will cau= se a failure. I'll put a thin ss shield here, with a bit of fibrefax glued = to back. So if muffler fails, it won't affect....."

=0A

Every forced l= anding had 10 little incidents in the past that preceded it. Your risk isn'= t some new cause. It's 1 of those 10 incidents that you rationalized away, = instead of saying:" that will happen to me too."

=0A

Good stuff.

= =0A


-al wick
Cozy IV with 3.0 liter Subaru
230+ hrs tt from Por= tland, Oregon

---------- Original Message ----------
From: Mark S= teitle <msteitle@gmail.com>
To: "Rotary motors in aircraft" <fl= yrotary@lancaironline.net>
Subject: [FlyRotary] Re: Gary Casey was [F= lyRotary] Re: Rotary Engines
Date: Sun, 12 Apr 2009 06:45:24 -0500
Mike,

Has anyone ever tried to document the rotary incidents resu= lting in a forced landing?

Here's what I recall from memory, so it l= ikely is missing a few;
 
    3 forced landings d= ue to ruptured oil coolers
    1 forced landing due to a= pex seal coming out of its slot (rotor out of spec)
    1= forced landing due to improper assembly of engine (seal wedged between rot= or & side housing)
    1 forced landing on highway du= e to catastrophic overheating of engine
    2 forced landings (one fatal) due to probable fuel system design flaw 
&nb= sp;   1 forced landing on highway due to ingestion of FOD.  =

There were a few others, such as turbo failures which allowed for c= ontinued operation at reduced power, so we may or may not wish to include t= hose here. 

While a number of these incidents date back quite = a few years, and we have made excellent progress, it says to me that we sti= ll have room for improvement in the peripheral department.  The good n= ews is that out of all of the incidents listed above, none of them were cau= sed by a true engine failure.  That's where the rotary has really earn= ed my respect as a viable a/c engine.

Pay attention to the details! =

Mark S.


=0A
On Sat, Apr 1= 1, 2009 at 9:22 PM, Mike Wills <rv-4mike@cox.net> wrote:
=0A
=0A
=0A
This has been an interesting thread. In the end, = it doesnt really matter how many "major" parts you have - even a minor fail= ure can bring you down. While I believe the basic rotary engine itself is m= ore fault tolerant than a recip, the peripherals used in the typical rotary= install are a lot more complex than a typical recip install. Since we rota= ry fliers dont have the benefit of 70 years worth of experience flying behi= nd the typical LyCon farm implement I think overall our odds are considerab= ly worse. Comes down to how well an individual engineer's his installation = and there is a tremendous amount of variation here.
=0A
&nb= sp;
=0A
The dependence on electron= ics in the typical rotary install  is a good example. I may be a littl= e sensitive to this issue since I've been trying to find an intermitte= nt glitch (2 times in 22 hours of engine testing).
=0A
&nbs= p;
=0A
Mik= e Wills
=0A
RV-4 N144MW  
=0A
=0A
=0A
----- Original Message -----
=0A
<= b>From: Ed Anderson
=0A
=0A
=0A
=0A
=0A
Sent: Saturday, Apri= l 11, 2009 7:31 AM
=0A
Subject: [FlyRotary] Gary Casey was [FlyRotary] Re: Rotary Eng= ines
=0A

=0A
=0A

Good analysis and logic, Gary.

=0A

 

=0A

You=E2=80=99d make a good addition to the =E2=80=9Crotary c= ommunity=E2=80=9D.  I have noticed over the 10 years I have been flyin= g my rotary powered RV-6A that the problems have decreased considerably, th= e success rate and completion rate has gone up and first flights are now oc= curring without significant problems =E2=80=93 even cooling is OK {:>).&= nbsp; I believe most of this improvement can be attributed to folks sharing= their knowledge, problems and solutions with others - such as on this list= . 

=0A

 = ;

=0A

I know that = fewer parts count is often touted as one of the rotary benefit =E2=80=93 an= d while it is true that the part count is lower, the most significant thing= (in my opinion) is not only does the lower part count help reliability (if= it is not there =E2=80=93 it can not break), but if you look a the design = of the eccentric shaft (for example) you notice the absence of the jogs in = a typical crankshaft and their stress points.  The thing is over 3=E2= =80=9D in diameter at some points and does not have the same inertia loads = born by a piston crankshaft.  The parts that are there are of very rob= ust design.  Finally, the rotary is (I believe) more tolerant of damag= e and tends to fail =E2=80=9Cgradually and gracefully=E2=80=9D, it can take= a licking and keep on ticking as the old saying goes.  Only extended = time and numbers will provide the true MTBF for the rotary, but I believe it looks very promising.

=0A

 

=0A

Failure of rotary engines are extremely rare, b= ut unfortunately, as with many alternative engine installations, auxiliary = subsystems such as fuel and ignition frequently being one-off designs have = been the cause of most failures =E2=80=93 with probably fuel the prime culp= rit.  The good news is that for some platforms (such as the RVs) we ha= ve pretty much established what will make an installation successful. = The Canard crowd is fast approaching that status with their somewhat more = challenging cooling requirements being over come.

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  Having lost a rotor during flight due t= o putting in high compression rotors with worn apex seal slots worn beyond = specs (found this out later =E2=80=93 my fault for not being aware of this = spec limit and checking it) which led to apex seal failure and consequence = lost of most of the power from one rotor, I was still able to maintain 6500= MSL at WOT and fuel mixture knob to full rich =E2=80=93 flowing 14.5 GPH = =E2=80=93 a lot of it undoubtedly  being blown through the disabled ro= tor.  Flew it back 60 miles to a suitable runway and made a non-eventf= ul landing.   There was a small increase in vibration due to the = power strokes no longer being balanced, but nothing bad and you could still= read the needles on the gauges.  Other folks have had FOD damage to a= rotor and also make it to a safe landing.  Two folks lost cooling (on= e loss of coolant fluid , one lost of water pump) and while they did cook the eng= ines, both made it back to a safe landing.  So all things considered, = I think the rotary continues to show that if the installation is designed p= roperly, it makes a very viable and reliable aircraft power plant.

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Failure of rotary engines i= n aircraft are extremely rare, but unfortunately, as with many alternative = engine installations, auxiliary subsystems such as fuel and ignition freque= ntly being one-off designs - have been the cause of most failures.  Th= e good news is that for some platforms (such as the RVs) we have pretty muc= h established what will make an installation successful.  The Canard c= rowd is fast approaching that status with their somewhat more challenging c= ooling requirements being over come.

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My rotary installation cost me $6500 back in 1996, the prim= ary cost being a rebuilt engine $2000 and the PSRU $2900.  I have sinc= e purchased a 1991 turbo block engine from Japan for $900 and rebuilt it my= self for another $2200.  My radiators (GM evaporator cores) cost $5.00= from the junk yard and another $50.00 each for having the bungs welded on.=   So depending on how much you buy and how much you build the price ca= n vary considerably.  Today, I would say it would take a minimum of ar= ound $8000 and more nominally around $10000 for a complete rotary installat= ion in an RV =E2=80=93 some folks could do it for less, some for more.

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But, regardless of the te= chnical merit (or not) in someone=E2=80=99s mind, the crucial thing (in my = opinion) is you need to address two personal factors:

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1.  What is your risk tolerance? = ; It doesn=E2=80=99t really matter how sexy some =E2=80=9Cexotic=E2=80=9D e= ngine installation may seem =E2=80=93 if you are not comfortable flying beh= ind (or in front) of it, then it certainly does not  makes sense to go= that route.  After all, this is supposed to have an element of fun an= d enjoyment to it.

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2.=   What is your knowledge, experience and background (and you don=E2=80= =99t have to be an engineer) and do you feel comfortable with the level of = involvement needed.

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S= o hope you continue to contribute to expanding our knowledge and understand= ing of the rotary in its application to power plant for aircraft.

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= Best Regards

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<= font size=3D"2" color=3D"navy" face=3D"Arial"> 

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Ed

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From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Gary Casey
Sent: Saturday, April 11, 2009 8:36 AM
<= b>To: Rotary motors in aircra= ft
Subject: [FlyRotary]= Re: Rotary Engines

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Just to add a few more comments and answers t= o the several excellent comments posted:

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How many parts does it take = to make a rotary rotate?  Well, "parts aren't parts" in this case. &nb= sp;Mark was right in that there are maybe 4 "major" components, but you hav= e to define major.  A piston engine certainly has far more major parts= .  Is a valve a "major" part?  I think so.  Is a rotor corne= r button a major part?  Not sure, but probably not.  Is each plan= et gear in the PSRU a major part?  I say yes, and the PSRU is an integ= ral part of the rotary engine.  As someone correctly pointed out, it's= not how many parts, but the reliability of the total system that counts. &= nbsp;Just looking at the history of the rotary (which, from the implication= of another post) it's not that good, but I don't think it has anything to = do with reliability of the concept.  It's more to do with the experime= ntal nature of the builds and installations.  My original point, perhaps not well expressed is that= to say there are just 4 parts is an oversimplification.  But let's fa= ce it, to put in an engine that has had many thousands of identical predece= ssors is less "experimental" than one that hasn't..

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Are we ES drivers= more conservative?  Probably so, since the ES is probably one of the = experimentals most similar to production aircraft, and not just because the= Columbia (can't force myself to say Cezzna :-) was a derivative.  The= refore, it tends to attract conservative builders and owners.  Not sur= prising then that almost all ES's have traditional powerplants, with the mo= st excellent exception of Mark.  While there may be more, I know of on= ly two off-airport landings caused by engine failures in the ES in almost 2= 0 years of experience.  One was caused by fuel starvation right after = takeoff (fatal) and one was caused by a PSRU failure in an auto engine conv= ersion.  So our old-fashioned conservative nature has served us pretty= well.

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Yes, I was assuming that the rotary had electronic fuel injec= tion and ignition, but that by itself doesn't change the inherent fuel effi= ciency of the engine.  Direct injection does have a potential to impro= ve BSFC because the fuel charge can be stratified.  It will probably d= ecrease available power, though.  I think the best rotary will be 5% l= ess efficient than the "best" piston engine(same refinements added to each)= .  But I stated that as a simple disadvantage - as Mark pointed out, i= t isn't that simple.  The rotary already comes configured to run on au= to gas.  The piston engine can also be so configured, but the compress= ion ratio reduction would reduce its BSFC and maybe durability advantage. &= nbsp;The total operating cost is certainly significantly less if auto gas c= an always be used to refuel.  I assumed in my assessment that it will = only be available 50% of the time.  The real disadvantage, which I failed to = state, is that the extra fuel required for a given mission might be 5 or 10= % higher and that negated the weight advantage, if only for long-range flig= hts.

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Is the engine less expensive?  I did a thorough analysis of= a direct-drive recip auto engine installation and my conclusion was that i= f the auto engine were equivalent in reliability to the aircraft engine it = would likely cost just as much.  Is the same true of the rotary?  = ;I'm not sure, but you have to consider the total cost, including engineeri= ng of all the parts in the system, not just the core engine.  I would = love to do a rotary installation, but I don't think I could justify it by c= ost reduction.

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It wasn't mentioned in the posts, but some have clai= med the rotary is "smoother" than a recip.  I at first resisted that n= otion.  Sure, any rotary given sufficient counterbalancing, is perfect= ly balanced.  A 4-cylinder opposed recip is not - there is a significa= nt secondary couple.  The 6-cylinder opposed engine is perfectly balan= ced, but only for PRIMARY and SECONDARY forces and couples - higher order f= orces have never really been analyzed, although they would be very small. &= nbsp;And then consider the forces within the engine that have to be resiste= d by that long, heavy, but flexible crankshaft.  So it isn't the mecha= nical balance that gives the rotary an advantage.  Let's take a look a= t the the torsional pulsations, comparing the 3-rotor against the 6-cylinde= r:  A 6-cylinder engine has 3 power impulses per rotation, as does the= 3-rotor, so they are the same, right?  Wrong.  They both incorporate 4 "stroke" c= ycles, meaning that there separate and sequential intake, compression, powe= r and exhaust events so that is the same for both.  The power event, w= hich is the source of the torque impulse, takes 1/2 of a crank rotatio= n for the recip.  In the rotary the power event requires 1/4 of a ROTO= R rotation, but the rotor rotates at 1/3 crank rotation - the result is tha= t the power impulse lasts 3/4 of a CRANK rotation, 50% longer than in a rec= ip.  Therefore, the torsional excitation delivered to the propeller, P= SRU and to the airframe is significantly less than for a recip.  And i= f you analyze the actual forces imparted, they go down by the square of the= rpm.  The torsional vibration amplitude goes down by a factor of 4 ju= st because the rpm of the rotary turns about twice as fast.  If you've= skipped to the bottom of the paragraph, as you probably should have :-), yes the rotary is "smoother" - a LOT smoother.. (my apologies to rota= ry purists, for simplicity I used the word "crankshaft" for both engines)

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But just because you can burn auto gas should you?  The biggest = problems with auto gas in recip aircraft have nothing to do with the engine= , but with the high vapor pressure of the fuel - it is more prone to vapor = lock.  The fuel systems of certified aircraft are not particularly wel= l designed with regard to vapor lock.  "Fortunately", rotary engines t= ypically have no mechanical fuel pump and are forced to rely on electric pu= mps.  Fortunately because the pumps can be located at the very bottom = of the aircraft and close to the fuel tanks, making vapor lock much less li= kely.  I would caution any builders to consider vapor lock possibiliti= es very seriously, much more so if you intend to run auto gas.  when I= was going to do this I planned to put one electric pump in the wing root o= f each wing, feeding the engine directly(the check valve in the non-running pump prevents back-feeding).  Redundancy was by a "crossfeed" line th= at could connect the tanks together.

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<= font size=3D"3" face=3D"Times New Roman">&= nbsp;

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And thanks, Mark for - probably = incorrectly - referring to me as a "good engineer".  I'll have to put = that in my resume!

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Have a good day,

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Gary

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(do you allow us outsiders = in your events?  I'll park well away :-)

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