X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao104.cox.net ([68.230.241.42] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3578704 for flyrotary@lancaironline.net; Sun, 12 Apr 2009 23:04:29 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.42; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao104.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20090413030353.GRAX16134.fed1rmmtao104.cox.net@fed1rmimpo03.cox.net> for ; Sun, 12 Apr 2009 23:03:53 -0400 Received: from wills ([68.105.85.56]) by fed1rmimpo03.cox.net with bizsmtp id er3q1b00C1CvZmk04r3tnd; Sun, 12 Apr 2009 23:03:53 -0400 X-Authority-Analysis: v=1.0 c=1 a=O-NgEC7ukE4A:10 a=aL-mqb72FDMA:10 a=UretUmmEAAAA:8 a=pGLkceISAAAA:8 a=kviXuzpPAAAA:8 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=Ia-xEzejAAAA:8 a=nUuTZ29dAAAA:8 a=6HJ_OvKRHZwD7Bh1CjMA:9 a=CLJolw2m0oxFazRgR-QA:7 a=_tpyZ-XWPGaLyAHH62XW5nEoCiEA:4 a=vNGxQsTWjH8A:10 a=iVkDmfvjeKcA:10 a=MSl-tDqOz04A:10 a=4vB-4DCPJfMA:10 a=EzXvWhQp4_cA:10 a=GfEOZt1HnSRx6b3R:21 a=DWGU22N5i-VxcjNc:21 a=Uuj3fea-oyJKAm137tsA:9 a=UfvjYhFs6j2jTM-gaK8A:7 a=SJBDC0lSzkH0a_-tq3fKAWa_4-wA:4 a=AfD3MYMu9mQA:10 X-CM-Score: 0.00 Message-ID: <07FD31FDEA284B8D938A565D6E912BDC@wills> From: "Mike Wills" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Gary Casey was [FlyRotary] Re: Rotary Engines Date: Sun, 12 Apr 2009 20:03:50 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_009F_01C9BBA9.CBE66170" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5512 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_009F_01C9BBA9.CBE66170 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Mark, I think this is a valuable tool - thanks for doing it. Not sure I can = add anything to your list since you arent naming names. :-) Although I = think that may result in some repeats on your list. Of course the other part of this still missing is flight hours and = thats going to be hard to accumulate. Documenting problems and trying to = determine MTBF without knowing how many hours are flown is obviously a = problem. You've already established a pretty significant list of issues. My = guess is that as a group the rotary crowd probably spends more time = tinkering and tweaking than flying compared with our LyCont = counterparts. Al least initially. Which would make the stats look even = worse. Just a guess. Mike Wills RV-4 N144MW ----- Original Message -----=20 From: Mark Steitle=20 To: Rotary motors in aircraft=20 Sent: Sunday, April 12, 2009 9:30 AM Subject: [FlyRotary] Re: Gary Casey was [FlyRotary] Re: Rotary Engines Al & Tracy,=20 Thanks for providing the additional history for my files. I have = started a spreadsheet of incidents which I will be happy to share at the = Texas Rotary Fly-In on May 29-31. The list has grown to 14. If anyone = has any "incidents" to share, please contact me off-list and I will add = them to my spreadsheet. To put everyone's mind at rest, I am not = listing names or tail numbers. They don't have to be catastrophic = failures, only something (related to the engine install) which could = have seriously affected the safe outcome of the flight. Please provide = date, description of incident, type a/c, and a description of what went = wrong. Just to make it perfectly clear, I'm not doing this to scare anyone, = or point fingers, only to help us to learn from others mistakes and = learn how to build safer rotary-powered aircraft. =20 Thanks, Mark On Sun, Apr 12, 2009 at 9:19 AM, Tracy Crook = wrote: Good list idea Mark. I'll add my 2 to the list. 1. Carb overheat (boiled fuel out of bowl) due to radiated heat = from nearby exhaust pipe. (added heat shield to fix) I was in process = of emergency landing but was able to restart engine so no actual forced = landing. =20 2. Loss of coolant due to coolant cap malfunction. (the cap = fitting had been modified so my fault again.) =20 Tracy On Sun, Apr 12, 2009 at 7:45 AM, Mark Steitle = wrote: Mike,=20 Has anyone ever tried to document the rotary incidents resulting = in a forced landing? Here's what I recall from memory, so it likely is missing a few; =20 3 forced landings due to ruptured oil coolers=20 1 forced landing due to apex seal coming out of its slot = (rotor out of spec) 1 forced landing due to improper assembly of engine (seal = wedged between rotor & side housing) 1 forced landing on highway due to catastrophic overheating of = engine 2 forced landings (one fatal) due to probable fuel system = design flaw =20 1 forced landing on highway due to ingestion of FOD. =20 There were a few others, such as turbo failures which allowed for = continued operation at reduced power, so we may or may not wish to = include those here. =20 While a number of these incidents date back quite a few years, and = we have made excellent progress, 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 above, none of them were caused by a true = engine failure. That's where the rotary has really earned my respect as = a viable a/c engine. Pay attention to the details!=20 Mark S.=20 On Sat, Apr 11, 2009 at 9:22 PM, Mike Wills = wrote: This has been an interesting thread. 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 engine itself is more = 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 = rotary fliers dont have the benefit of 70 years worth of experience = flying behind the typical LyCon farm implement I think overall our odds = are considerably worse. Comes down to how well an individual engineer's = his installation and there is a tremendous amount of variation here. The dependence on electronics in the typical rotary install is = a good example. I may be a little sensitive to this issue since I've = been trying to find an intermittent glitch (2 times in 22 hours of = engine testing). Mike Wills RV-4 N144MW =20 ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Saturday, April 11, 2009 7:31 AM Subject: [FlyRotary] Gary Casey was [FlyRotary] Re: Rotary = Engines Good analysis and logic, Gary. You=92d make a good addition to the =93rotary community=94. 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 flights are now occurring = without significant problems =96 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 this list. =20 I know that fewer parts count is often touted as one of the = rotary benefit =96 and 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 =96 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=94 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 robust design. Finally, the rotary is (I believe) = more tolerant of damage and tends to fail =93gradually and = gracefully=94, 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. Failure of rotary engines are extremely rare, but = 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 =96 with probably fuel the prime = culprit. The good news is that for some platforms (such as the RVs) we = have 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. Having lost a rotor during flight due to putting in high = compression rotors with worn apex seal slots worn beyond specs (found = this out later =96 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 =96 flowing 14.5 GPH =96 a lot of = it undoubtedly being blown through the disabled rotor. Flew it back 60 = miles to a suitable runway and made 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 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 (one loss of coolant fluid , one = lost of water pump) and while they did cook the engines, 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. Failure of rotary engines in aircraft are extremely rare, but = 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. The good news is that for some = platforms (such as the RVs) we have 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. My rotary installation 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 each 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 would take a minimum of = around $8000 and more nominally around $10000 for a complete rotary = installation in an RV =96 some folks could do it for less, some for = more. But, regardless of the technical merit (or not) in someone=92s = mind, the crucial thing (in my opinion) is you need to address two = personal factors: 1. What is your risk tolerance? It doesn=92t really matter = how sexy some =93exotic=94 engine installation may seem =96 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. 2. What is your knowledge, experience and background (and you = don=92t have to be an engineer) and do you feel comfortable with the = level of involvement needed. So hope you continue to contribute to expanding our knowledge = and understanding of the rotary in its application to power plant for = aircraft. Best Regards Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm ---------------------------------------------------------------------- From: Rotary motors in aircraft = [mailto:flyrotary@lancaironline.net] On Behalf Of Gary Casey Sent: Saturday, April 11, 2009 8:36 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Rotary Engines Just to add a few more comments and answers to the several = excellent comments posted: How many parts does it take to make a rotary rotate? Well, = "parts aren't parts" in this case. Mark was right in that 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" part? = I think so. Is a rotor corner button a major part? Not sure, but = probably not. Is each planet gear in the PSRU a major part? I say yes, = and the PSRU is an integral 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. 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 experimental 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 face it, to put in an = engine that has had many thousands of identical predecessors is less = "experimental" than one that hasn't.. 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. Therefore, it tends to attract = conservative builders and owners. Not surprising then that almost all = ES's have traditional powerplants, with the most excellent exception of = Mark. While there may be more, I know of only two off-airport landings = caused by engine failures in the ES in almost 20 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 conversion. So our = old-fashioned conservative nature has served us pretty well. Yes, I was assuming that the rotary had electronic fuel = injection and ignition, but that by itself doesn't change the inherent = fuel efficiency of the engine. Direct injection does have a potential = to improve BSFC because the fuel charge can be stratified. It will = probably decrease available power, though. I think the best rotary will = be 5% less efficient than the "best" piston engine(same refinements = added to each). But I stated that as a simple disadvantage - as Mark = 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 advantage. The total operating cost is certainly = significantly less if auto gas can 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 flights. Is the engine less expensive? I did a thorough analysis of a = direct-drive recip auto engine installation and 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, including 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 justify it by = cost reduction. It wasn't mentioned in the posts, but some have claimed the = rotary is "smoother" than a recip. I at first resisted that notion. = Sure, any rotary given sufficient counterbalancing, is perfectly = balanced. A 4-cylinder opposed recip is not - there is a significant = secondary couple. The 6-cylinder opposed engine is perfectly balanced, = but only for PRIMARY and SECONDARY forces and couples - higher order = forces have never really been analyzed, although they would be very = small. And then consider 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 gives the rotary an advantage. Let's take a = look at the the torsional pulsations, comparing the 3-rotor against the = 6-cylinder: 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" cycles, meaning that there 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 result is that the power impulse lasts 3/4 of a = CRANK rotation, 50% longer than in a recip. Therefore, the torsional = excitation delivered to the propeller, 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 the rpm. The torsional = vibration amplitude goes down by a factor of 4 just 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 rotary purists, for = simplicity I used the word "crankshaft" for both engines) 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 well designed with regard to vapor lock. "Fortunately", = rotary engines typically have no mechanical fuel pump and are forced to = rely on electric pumps. 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 likely. I would caution any builders to consider = vapor lock possibilities 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 of each wing, feeding the engine directly(the = check valve in the non-running pump prevents back-feeding). Redundancy = was by a "crossfeed" line that could connect the tanks together. And thanks, Mark for - probably incorrectly - referring to me = as a "good engineer". I'll have to put that in my resume! Have a good day, Gary (do you allow us outsiders in your events? I'll park well = away :-) __________ Information from ESET NOD32 Antivirus, version of = virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_009F_01C9BBA9.CBE66170 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Mark,
 
 I think this is a valuable tool - = thanks for=20 doing it. Not sure I can add anything to your list since you arent = naming names.=20 :-)  Although I think that may result in some repeats on your=20 list.
 
 Of course  the other part of = this still=20 missing is flight hours and thats going to be hard to accumulate. = Documenting=20 problems and trying to determine MTBF without knowing how many = hours are=20 flown is obviously a problem.
 
 You've already established a = pretty=20 significant  list of issues. My guess is that as a group the rotary = crowd=20 probably spends more time tinkering and tweaking than flying compared = with our=20 LyCont counterparts. Al least initially. Which would make the stats = look=20 even worse. Just a guess.
 
Mike Wills
RV-4 N144MW
----- Original Message -----
From:=20 Mark = Steitle=20
Sent: Sunday, April 12, 2009 = 9:30=20 AM
Subject: [FlyRotary] Re: Gary = Casey was=20 [FlyRotary] Re: Rotary Engines

Al & Tracy,

Thanks for providing the = additional=20 history for my files.  I have started a spreadsheet of incidents = which I=20 will be happy to share at the Texas Rotary Fly-In on May 29-31.  = The list=20 has grown to 14.  If anyone has any "incidents" to share, please = contact=20 me off-list and I will add them to my spreadsheet.  To put = everyone's=20 mind at rest, I am not listing names or tail numbers.  They don't = have to=20 be catastrophic failures, only something (related to the engine = install) which=20 could have seriously affected the safe outcome of the flight.  = Please=20 provide date, description of incident, type a/c, and a description of = what=20 went wrong.

Just to make it perfectly clear, I'm not doing this = to=20 scare anyone, or point fingers, only to help us to learn from others = mistakes=20 and learn how to build safer rotary-powered aircraft. =20

Thanks,
Mark

On Sun, Apr 12, 2009 at 9:19 AM, Tracy Crook = <tracy@rotaryaviation.com>= =20 wrote:
Good=20 list idea Mark.  I'll add my 2 to the list.

1.  = Carb=20 overheat (boiled fuel out of bowl)  due to radiated heat from = nearby=20 exhaust pipe. (added heat shield to fix)  I was in process of = emergency=20 landing but was able to restart engine so no actual forced = landing. =20

2.  Loss of coolant due to coolant cap = malfunction.  (the=20 cap fitting had been modified so my fault again.) 

Tracy



On Sun, Apr 12, 2009 at 7:45 AM, Mark = Steitle <msteitle@gmail.com> wrote:
Mike,=20

Has anyone ever tried to document the rotary incidents = resulting=20 in a forced landing?

Here's what I recall from memory, so = it likely=20 is missing a few;
 
    3 forced = landings due to=20 ruptured oil coolers
    1 forced landing due = to apex=20 seal coming out of its slot (rotor out of = spec)
    1=20 forced landing due to improper assembly of engine (seal wedged = between=20 rotor & side housing)
    1 forced landing = on=20 highway due to catastrophic overheating of = engine
    2=20 forced landings (one fatal) due to probable fuel system design = flaw =20
    1 forced landing on highway due to = ingestion of=20 FOD. 

There were a few others, such as turbo failures = which=20 allowed for continued operation at reduced power, so we may or may = not=20 wish to include those here. 

While a number of these=20 incidents date back quite a few years, and we have made excellent=20 progress, it says to me that we still have room for improvement in = the=20 peripheral department.  The good news is that out of all of = the=20 incidents listed above, none of them were caused by a true engine=20 failure.  That's where the rotary has really earned my = respect as a=20 viable a/c engine.

Pay attention to the details! =

Mark S.=20


On Sat, Apr 11, 2009 at 9:22 PM, Mike = Wills <rv-4mike@cox.net> wrote:
This has been an interesting = thread. In the=20 end, it doesnt really matter how many "major" parts you have - = even a=20 minor failure can bring you down. While I believe the basic = rotary=20 engine itself is more fault tolerant than a recip, the = peripherals used=20 in the typical rotary install are a lot more complex than a = typical=20 recip install. Since we rotary fliers dont have the benefit of = 70 years=20 worth of experience flying behind the typical LyCon farm = implement I=20 think overall our odds are considerably worse. Comes down to how = well an=20 individual engineer's his installation and there is a tremendous = amount=20 of variation here.
 
The dependence on electronics = in the=20 typical rotary install  is a good example. I may be a=20 little sensitive to this issue since I've been trying to = find an=20 intermittent glitch (2 times in 22 hours of engine=20 testing).
 
Mike Wills
RV-4 = N144MW  
-----=20 Original Message -----
From:=20 Ed = Anderson=20
To:=20 Rotary motors=20 in aircraft
Sent:=20 Saturday, April 11, 2009 7:31 AM
Subject:=20 [FlyRotary] Gary Casey was [FlyRotary] Re: Rotary = Engines

Good analysis=20 and logic, Gary.

 

You=92d make a=20 good addition to the =93rotary community=94.  I have = noticed over the=20 10 years I have been flying my rotary powered RV-6A that the = problems=20 have decreased considerably, the success rate and completion = rate has=20 gone up and first flights are now occurring without = significant=20 problems =96 even cooling is OK {:>).  I believe most = of this=20 improvement can be attributed to folks sharing their = knowledge,=20 problems and solutions with others - such as on this = list. =20

 

I = know that=20 fewer parts count is often touted as one of the rotary benefit = =96 and=20 while it is true that the part count is lower, the most = significant=20 thing (in my opinion) is not only does the lower part count = help=20 reliability (if it is not there =96 it can not break), but if = you look a=20 the design of the eccentric shaft (for example) you notice the = absence=20 of the jogs in a typical crankshaft and their stress = points.  The=20 thing is over 3=94 in diameter at some points and does not = have the same=20 inertia loads born by a piston crankshaft.  The parts = that are=20 there are of very robust design.  Finally, the rotary is = (I=20 believe) more tolerant of damage and tends to fail = =93gradually and=20 gracefully=94, it can take a licking and keep on ticking as = the old=20 saying goes.  Only extended time and numbers will provide = the=20 true MTBF for the rotary, but I believe it looks very=20 promising.

 

Failure of=20 rotary engines are extremely rare, but unfortunately, as with = many=20 alternative engine installations, auxiliary subsystems such as = fuel=20 and ignition frequently being one-off designs have been the = cause of=20 most failures =96 with probably fuel the prime culprit.  = The good=20 news is that for some platforms (such as the RVs) we have = pretty much=20 established what will make an installation successful.  = The=20 Canard crowd is fast approaching that status with their = somewhat more=20 challenging cooling requirements being over = come.

 

  Having=20 lost a rotor during flight due to putting in high compression = rotors=20 with worn apex seal slots worn beyond specs (found this out = later =96 my=20 fault for not being aware of this spec limit and checking it) = which=20 led to apex seal failure and consequence lost of most of the = power=20 from one rotor, I was still able to maintain 6500 MSL at WOT = and fuel=20 mixture knob to full rich =96 flowing 14.5 GPH =96 a lot of it = undoubtedly=20  being blown through the disabled rotor.  Flew it = back 60=20 miles to a suitable runway and made a non-eventful=20 landing.   There was a small increase in vibration = due to=20 the power strokes no longer being balanced, but nothing bad = and you=20 could still read the needles on the gauges.  Other folks = have had=20 FOD damage to a rotor and also make it to a safe = landing.  Two=20 folks lost cooling (one loss of coolant fluid , one lost of = water=20 pump) and while they did cook the engines, both made it back = to a safe=20 landing.  So all things considered, I think the rotary = continues=20 to show that if the installation is designed properly, it = makes a very=20 viable and reliable aircraft power plant.

 

Failure of=20 rotary engines in aircraft are extremely rare, but = unfortunately, as=20 with many alternative engine installations, auxiliary = subsystems such=20 as fuel and ignition frequently being one-off designs - have = been the=20 cause of most failures.  The good news is that for some = platforms=20 (such as the RVs) we have pretty much established what will = make an=20 installation successful.  The Canard crowd is fast = approaching=20 that status with their somewhat more challenging cooling = requirements=20 being over come.

 

My = rotary=20 installation cost me $6500 back in 1996, the primary cost = being a=20 rebuilt engine $2000 and the PSRU $2900.  I have since = purchased=20 a 1991 turbo block engine from Japan for $900 and rebuilt it = myself=20 for another $2200.  My radiators (GM evaporator cores) = cost $5.00=20 from the junk yard and another $50.00 each for having the = bungs welded=20 on.  So depending on how much you buy and how much you = build the=20 price can vary considerably.  Today, I would say it would = take a=20 minimum of around $8000 and more nominally around $10000 for a = complete rotary installation in an RV =96 some folks could do = it for=20 less, some for more.

 

But,=20 regardless of the technical merit (or not) in someone=92s = mind, the=20 crucial thing (in my opinion) is you need to address two = personal=20 factors:

 

1.  What=20 is your risk tolerance?  It doesn=92t really matter how = sexy some=20 =93exotic=94 engine installation may seem =96 if you are not = comfortable=20 flying behind (or in front) of it, then it certainly does not=20  makes sense to go that route.  After all, this is = supposed=20 to have an element of fun and enjoyment to = it.

 

2.  What=20 is your knowledge, experience and background (and you don=92t = have to be=20 an engineer) and do you feel comfortable with the level of = involvement=20 needed.

 

So = hope you=20 continue to contribute to expanding our knowledge and = understanding of=20 the rotary in its application to power plant for=20 aircraft.

 

 

Best=20 Regards

 

Ed

 

 

Ed=20 Anderson

Rv-6A N494BW=20 Rotary Powered

Matthews,=20 NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html<= /P>

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

From:=20 Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Gary=20 Casey
Sent: = Saturday,=20 April 11, 2009 8:36 AM
To: Rotary motors in=20 aircraft
Subject:=20 [FlyRotary] Re: Rotary Engines

 

Just to add a few more comments and = answers to=20 the several excellent comments posted:

 

How many parts does it take to make = a rotary=20 rotate?  Well, "parts aren't parts" in this case. =  Mark was=20 right in that there are maybe 4 "major" components, but you = have to=20 define major.  A piston engine certainly has far more = major=20 parts.  Is a valve a "major" part?  I think so. =  Is a=20 rotor corner button a major part?  Not sure, but probably = not.=20  Is each planet gear in the PSRU a major part?  I = say yes,=20 and the PSRU is an integral part of the rotary engine. =  As=20 someone correctly pointed out, it's not how many parts, but = the=20 reliability of the total system that counts.  Just = looking at the=20 history of the rotary (which, from the implication of another = post)=20 it's not that good, but I don't think it has anything to do = with=20 reliability of the concept.  It's more to do with the=20 experimental nature of the builds and installations.  My = original=20 point, perhaps not well expressed is that to say there are = just 4=20 parts is an oversimplification.  But let's face it, to = put in an=20 engine that has had many thousands of identical predecessors = is less=20 "experimental" than one that hasn't..

 

Are we ES drivers more conservative? =  Probably so, since the ES is probably one of the = experimentals=20 most similar to production aircraft, and not just because the = Columbia=20 (can't force myself to say Cezzna :-) was a derivative.=20  Therefore, it tends to attract conservative builders and = owners.=20  Not surprising then that almost all ES's have = traditional=20 powerplants, with the most excellent exception of Mark. =  While=20 there may be more, I know of only two off-airport landings = caused by=20 engine failures in the ES in almost 20 years of experience. =  One=20 was caused by fuel starvation right after takeoff (fatal) and = one was=20 caused by a PSRU failure in an auto engine conversion. =  So our=20 old-fashioned conservative nature has served us pretty=20 well.

 

Yes, I was assuming that the rotary = had=20 electronic fuel injection and ignition, but that by itself = doesn't=20 change the inherent fuel efficiency of the engine. =  Direct=20 injection does have a potential to improve BSFC because the = fuel=20 charge can be stratified.  It will probably decrease = available=20 power, though.  I think the best rotary will be 5% less = efficient=20 than the "best" piston engine(same refinements added to each). =  But I stated that as a simple disadvantage - as Mark = pointed=20 out, it isn't that simple.  The rotary already comes = configured=20 to run on auto gas.  The piston engine can also be so = configured,=20 but the compression ratio reduction would reduce its BSFC and = maybe=20 durability advantage.  The total operating cost is = certainly=20 significantly less if auto gas can always be used to refuel. =  I=20 assumed in my assessment that it will only be available 50% of = the=20 time.  The real disadvantage, which I failed to state, is = that=20 the extra fuel required for a given mission might be 5 or 10% = higher=20 and that negated the weight advantage, if only for long-range=20 flights.

 

Is the engine less expensive? =  I did a=20 thorough analysis of a direct-drive recip auto engine = installation and=20 my conclusion was that if the auto engine were equivalent in=20 reliability to the aircraft engine it would likely cost just = as much.=20  Is the same true of the rotary?  I'm not sure, but = you have=20 to consider the total cost, including engineering of all the = parts in=20 the system, not just the core engine.  I would love to do = a=20 rotary installation, but I don't think I could justify it by = cost=20 reduction.

 

It wasn't mentioned in the posts, = but some=20 have claimed the rotary is "smoother" than a recip.  I at = first=20 resisted that notion.  Sure, any rotary given sufficient=20 counterbalancing, is perfectly balanced.  A 4-cylinder = opposed=20 recip is not - there is a significant secondary couple. =  The=20 6-cylinder opposed engine is perfectly balanced, but only for = PRIMARY=20 and SECONDARY forces and couples - higher order forces have = never=20 really been analyzed, although they would be very small. =  And=20 then consider the forces within the engine that have to be = resisted by=20 that long, heavy, but flexible crankshaft.  So it isn't = the=20 mechanical balance that gives the rotary an advantage. =  Let's=20 take a look at the the torsional pulsations, comparing the = 3-rotor=20 against the 6-cylinder:  A 6-cylinder engine has 3 power = impulses=20 per rotation, as does the 3-rotor, so they are the same, = right?=20  Wrong.  They both incorporate 4 "stroke" cycles, = meaning=20 that there separate and sequential intake, compression, power = and=20 exhaust events so that is the same for both.  The power = event,=20 which is the source of the torque impulse, takes 1/2 of a = crank=20 rotation for the recip.  In the rotary the power event = requires=20 1/4 of a ROTOR rotation, but the rotor rotates at 1/3 crank = rotation -=20 the result is that the power impulse lasts 3/4 of a CRANK = rotation,=20 50% longer than in a recip.  Therefore, the torsional = excitation=20 delivered to the propeller, PSRU and to the airframe is = significantly=20 less than for a recip.  And if you analyze the actual = forces=20 imparted, they go down by the square of the rpm.  The = torsional=20 vibration amplitude goes down by a factor of 4 just because = the rpm of=20 the rotary turns about twice as fast.  If you've skipped = to the=20 bottom of the paragraph, as you probably should have :-), yes = the=20 rotary is "smoother" - a LOT smoother.. (my apologies to = rotary=20 purists, for simplicity I used the word "crankshaft" for both=20 engines)

 

But just because you can burn auto = gas should=20 you?  The biggest problems with auto gas in recip = aircraft have=20 nothing to do with the engine, but with the high vapor = pressure of the=20 fuel - it is more prone to vapor lock.  The fuel systems = of=20 certified aircraft are not particularly well designed with = regard to=20 vapor lock.  "Fortunately", rotary engines typically have = no=20 mechanical fuel pump and are forced to rely on electric pumps. =  Fortunately because the pumps can be located at the very = bottom=20 of the aircraft and close to the fuel tanks, making vapor lock = much=20 less likely.  I would caution any builders to consider = vapor lock=20 possibilities very seriously, much more so if you intend to = run auto=20 gas.  when I was going to do this I planned to put one = electric=20 pump in the wing root of each wing, feeding the engine = directly(the=20 check valve in the non-running pump prevents back-feeding).=20  Redundancy was by a "crossfeed" line that could connect = the=20 tanks together.

 

And thanks, Mark for - probably = incorrectly -=20 referring to me as a "good engineer".  I'll have to put = that in=20 my resume!

 

Have a good = day,

Gary

(do you allow us outsiders in your = events?=20  I'll park well away :-)

 




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