X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from outbound-mail.vgs.untd.com ([64.136.55.15] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3578166 for flyrotary@lancaironline.net; Sun, 12 Apr 2009 11:14:59 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.55.15; envelope-from=alwick@juno.com Received: from outbound-bu1.vgs.untd.com (webmail24.vgs.untd.com [10.181.12.164]) by smtpout05.vgs.untd.com with SMTP id AABE8EBLBAWA3J8J for (sender ); Sun, 12 Apr 2009 08:14:09 -0700 (PDT) X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkG5955tqS+mg96sh8GAzLbpFZCGhaQ6+jA== Received: (from alwick@juno.com) by webmail24.vgs.untd.com (jqueuemail) id PDX5BSQH; Sun, 12 Apr 2009 08:13:48 PDT Received: from [10.181.11.40] by webmail24.vgs.untd.com with HTTP: Sun, 12 Apr 2009 15:13:00 GMT X-Originating-IP: [10.181.11.40] Mime-Version: 1.0 From: "al wick" Date: Sun, 12 Apr 2009 15:13:00 GMT To: flyrotary@lancaironline.net Subject: Re: forced landings X-Mailer: Webmail Version 4.0 Message-Id: <20090412.081300.5158.0@webmail24.vgs.untd.com> Content-Type: multipart/alternative;boundary="--__JWM__J721a.7333S.4063M" X-ContentStamp: 18:9:2149802940 X-MAIL-INFO:23a950b0d051495051c950d0b40120e5e0fd0d903da5e100e0e0cd64d46459c0d05d30893041114138195d382534c0351d54b55031a975a4711d24dd016d2419b4a405d121d4f4b54dc4855555d964cde0cd9100ad91e059e1e0a0f1c0384d813df014bd953d4d29d929ad75bd1029c035d465d140991dd4f41df4ddd129c02070ade1a9c9450050315d75f131393124c950941d7550716d54edd0ed7d15094d608444f54d443d4da529916d04719d957974c130c1bd55602538bd71b9b9597905bd8d8109848184f5bdb905e9902020a56529e4914971743d8d49f9f4ad49e5a989e0f949994df5e12da41974d075d0500d50b4ed0435fded5d 00e5d0b431dd35547d553030e1d1f41138195d11c4cd0471e9557104091d991925d93df5bd4d794d95940d1481b98009cd101029a5643d319184a0 X-UNTD-Peer-Info: 10.181.12.164|webmail24.vgs.untd.com|outbound-bu1.vgs.untd.com|alwick@juno.com ----__JWM__J721a.7333S.4063M Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Content-Type: text/plain; charset=windows-1252 Absolutely excellent Mark. I'd encourage you to get the year the inciden= t occured too. That will be your proof of reduced risk from things like = this newsgroup. = Avoid the black and white approach: forced landing or not forced. Becaus= e 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 did precautionary landing. If y= ou also explain what happened, then a reader can easily tell you were ob= jective in your rating. = 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 h= ear of incident. A wild assed guess is ok, if you just base the guess on= some facts. For example, you could check faa database and find 100 plan= es registered with rotary engine in 2005. You can guess that equals 70 h= ours each. Even though it's a wild assed guess, it will still be excelle= nt predictor of change over time. Each year you have the same "error". S= o your numbers WILL reflect improvement. More 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 "contrib= uting factors". Then you can dramatically reduce personal risk. Good exa= mple: We had that guy that installed plastic fuel flow sensor in fuel li= ne. It melted, he died. Tracy just reported hot exhaust caused fuel to b= oil 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 c= ause a failure. I'll put a thin ss shield here, with a bit of fibrefax g= lued to back. So if muffler fails, it won't affect....." Every forced landing had 10 little incidents in the past that preceded i= t. 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." Good stuff. -al wick Cozy IV with 3.0 liter Subaru 230+ hrs tt from Portland, Oregon ---------- Original Message ---------- From: Mark Steitle To: "Rotary motors in aircraft" Subject: [FlyRotary] Re: Gary Casey was [FlyRotary] Re: Rotary Engines Date: Sun, 12 Apr 2009 06:45:24 -0500 Mike, = Has anyone ever tried to document the rotary incidents resulting in a fo= rced landing? Here's what I recall from memory, so it likely is missing a few; = 3 forced landings due to ruptured oil coolers = 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 bet= ween rotor & side housing) 1 forced landing on highway due to catastrophic overheating of engin= e 2 forced landings (one fatal) due to probable fuel system design fla= w = 1 forced landing on highway due to ingestion of FOD. = There were a few others, such as turbo failures which allowed for contin= ued operation at reduced power, so we may or may not wish to include tho= se here. = While a number of these incidents date back quite a few years, and we ha= ve made excellent progress, it says to me that we still have room for im= provement in the peripheral department. The good news is that out of al= l of the incidents listed above, none of them were caused by a true engi= ne failure. That's where the rotary has really earned my respect as a v= iable a/c engine. Pay attention to the details! = Mark S. = 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 do= wn. While I believe the basic rotary engine itself is more fault toleran= t 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 d= ont have the benefit of 70 years worth of experience flying behind the t= ypical LyCon farm implement I think overall our odds are considerably wo= rse. Comes down to how well an individual engineer's his installation an= d there is a tremendous amount of variation here. The dependence on elec= tronics in the typical rotary install is a good example. I may be a lit= tle sensitive to this issue since I've been trying to find an intermitte= nt glitch (2 times in 22 hours of engine testing). Mike WillsRV-4 N144MW= ----- Original Message ----- From: Ed Anderson To: Rotary motors in ai= rcraft Sent: Saturday, April 11, 2009 7:31 AMSubject: [FlyRotary] Gary C= asey was [FlyRotary] Re: Rotary Engines Good analysis and logic, Gary. = You=92d make a good addition to the =93rotary community=94. I have noti= ced over the 10 years I have been flying my rotary powered RV-6A that th= e 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 improveme= nt can be attributed to folks sharing their knowledge, problems and solu= tions with others - such as on this list. = = I know that fewer parts count is often touted as one of the rotary benef= it =96 and while it is true that the part count is lower, the most signi= ficant 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 inert= ia loads born by a piston crankshaft. The parts that are there are of v= ery robust design. Finally, the rotary is (I believe) more tolerant of = damage and tends to fail =93gradually and gracefully=94, it can take a l= icking and keep on ticking as the old saying goes. Only extended time a= nd numbers will provide the true MTBF for the rotary, but I believe it l= ooks very promising. = Failure of rotary engines are extremely rare, but unfortunately, as with= many alternative engine installations, auxiliary subsystems such as fue= l and ignition frequently being one-off designs have been the cause of m= ost failures =96 with probably fuel the prime culprit. The good news is= that for some platforms (such as the RVs) we have pretty much establish= ed what will make an installation successful. The Canard crowd is fast = approaching that status with their somewhat more challenging cooling req= uirements being over come. = Having lost a rotor during flight due to putting in high compression r= otors 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) whi= ch led to apex seal failure and consequence lost of most of the power fr= om one rotor, I was still able to maintain 6500 MSL at WOT and fuel mixt= ure 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 suit= able runway and made a non-eventful landing. There was a small increas= e in vibration due to the power strokes no longer being balanced, but no= thing bad and you could still read the needles on the gauges. Other fol= ks have had FOD damage to a rotor and also make it to a safe landing. T= wo folks lost cooling (one loss of coolant fluid , one lost of water pum= p) and while they did cook the engines, both made it back to a safe land= ing. So all things considered, I think the rotary continues to show tha= t if the installation is designed properly, it makes a very viable and r= eliable aircraft power plant. = Failure of rotary engines in aircraft are extremely rare, but unfortunat= ely, 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 (s= uch as the RVs) we have pretty much established what will make an instal= lation successful. The Canard crowd is fast approaching that status wit= h their somewhat more challenging cooling requirements being over come. = My rotary installation cost me $6500 back in 1996, the primary cost bein= g a rebuilt engine $2000 and the PSRU $2900. I have since purchased a 1= 991 turbo block engine from Japan for $900 and rebuilt it myself for ano= ther $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 depend= ing on how much you buy and how much you build the price can vary consid= erably. 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 facto= rs: = 1. What is your risk tolerance? It doesn=92t really matter how sexy so= me =93exotic=94 engine installation may seem =96 if you are not comforta= ble 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 h= ave to be an engineer) and do you feel comfortable with the level of inv= olvement needed. = So hope you continue to contribute to expanding our knowledge and unders= tanding 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 com= ments 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 ha= s far more major parts. Is a valve a "major" part? I think so. Is a r= otor corner button a major part? Not sure, but probably not. Is each p= lanet gear in the PSRU a major part? I say yes, and the PSRU is an inte= gral 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 experim= ental nature of the builds and installations. My original point, perhap= s not well expressed is that to say there are just 4 parts is an oversim= plification. But let's face it, to put in an engine that has had many t= housands of identical predecessors is less "experimental" than one that = hasn't.. = Are we ES drivers more conservative? Probably so, since the ES is proba= bly one of the experimentals most similar to production aircraft, and no= t just because the Columbia (can't force myself to say Cezzna :-) was a = derivative. Therefore, it tends to attract conservative builders and ow= ners. Not surprising then that almost all ES's have traditional powerpl= ants, with the most excellent exception of Mark. While there may be mor= e, 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 starvat= ion 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 ig= nition, but that by itself doesn't change the inherent fuel efficiency o= f the engine. Direct injection does have a potential to improve BSFC be= cause the fuel charge can be stratified. It will probably decrease avai= lable power, though. I think the best rotary will be 5% less efficient = than the "best" piston engine(same refinements added to each). But I st= ated 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 pi= ston engine can also be so configured, but the compression ratio reducti= on would reduce its BSFC and maybe durability advantage. The total oper= ating cost is certainly significantly less if auto gas can always be use= d 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 tha= t the extra fuel required for a given mission might be 5 or 10% higher a= nd that negated the weight advantage, if only for long-range flights. = Is the engine less expensive? I did a thorough analysis of a direct-dri= ve recip auto engine installation and my conclusion was that if the auto= engine were equivalent in reliability to the aircraft engine it would l= ikely 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 t= he 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 reduct= ion. = It wasn't mentioned in the posts, but some have claimed the rotary is "s= moother" than a recip. I at first resisted that notion. Sure, any rota= ry given sufficient counterbalancing, is perfectly balanced. A 4-cylind= er opposed recip is not - there is a significant secondary couple. The = 6-cylinder opposed engine is perfectly balanced, but only for PRIMARY an= d SECONDARY forces and couples - higher order forces have never really b= een analyzed, although they would be very small. And then consider the = forces within the engine that have to be resisted by that long, heavy, b= ut flexible crankshaft. So it isn't the mechanical balance that gives t= he rotary an advantage. Let's take a look at the the torsional pulsatio= ns, comparing the 3-rotor against the 6-cylinder: A 6-cylinder engine h= as 3 power impulses per rotation, as does the 3-rotor, so they are the s= ame, right? Wrong. They both incorporate 4 "stroke" cycles, meaning th= at there separate and sequential intake, compression, power and exhaust = events so that is the same for both. The power event, which is the sour= ce 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 impul= se 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 a= irframe 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 tors= ional vibration amplitude goes down by a factor of 4 just because the rp= m of the rotary turns about twice as fast. If you've skipped to the bot= tom of the paragraph, as you probably should have :-), yes the rotary is= "smoother" - a LOT smoother.. (my apologies to rotary purists, for simp= licity 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 lo= ck. The fuel systems of certified aircraft are not particularly well de= signed with regard to vapor lock. "Fortunately", rotary engines typical= ly 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 th= e aircraft and close to the fuel tanks, making vapor lock much less like= ly. I would caution any builders to consider vapor lock possibilities v= ery seriously, much more so if you intend to run auto gas. when I was g= oing to do this I planned to put one electric pump in the wing root of e= ach 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 signa= ture database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ----__JWM__J721a.7333S.4063M Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Content-Type: text/html; charset=windows-1252

Absolutely excellent Mark. I'd encourage you to get the year th= e incident occured too. That will be your proof of reduced risk from thi= ngs like this newsgroup.

Avoid the black and white approach: forced landing or not forced. Bec= ause 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 did precautionary landi= ng. If you also explain what happened, then a reader can easily tell you= were objective in your rating.

The final piece is about how many flight hours, first flights there w= ere. Each year there are more engines flying, so way more likely you wil= l hear of incident. A wild assed guess is ok, if you just base the guess= on some facts. For example, you could check faa database and find 100 p= lanes registered with rotary engine in 2005. You can guess that equals 7= 0 hours each. Even though it's a wild assed guess, it will still be exce= llent predictor of change over time. Each year you have the same "error"= . So your numbers WILL reflect improvement.

More important than anything. If you can force your self to say: "Tha= t same failure will happen to me". Particularly if you can look at "cont= ributing factors". Then you can dramatically reduce personal risk. Good = 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 t= o boil 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 hea= t will cause a failure. I'll put a thin ss shield here, with a bit of fi= brefax glued to back. So if muffler fails, it won't affect....."

Every forced landing had 10 little incidents in the past that precede= d 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."<= /P>

Good stuff.


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

---------- Original Message ----------
From: Mar= k Steitle <msteitle@gmail.com>
To: "Rotary motors in aircraft" = <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Gary Cas= ey was [FlyRotary] Re: Rotary Engines
Date: Sun, 12 Apr 2009 06:45:24= -0500

Mike,

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

Here's what I recall fr= om memory, so it likely is missing a few;
 
   = ; 3 forced landings due to ruptured oil coolers
    1= forced landing due to apex seal coming out of its slot (rotor out of sp= ec)
    1 forced landing due to improper assembly of e= ngine (seal wedged between rotor & side housing)
  &nbs= p; 1 forced landing on highway due to catastrophic overheating of engine=
    2 forced landings (one fatal) due to probable fue= l system design flaw 
    1 forced landing on hi= ghway due to ingestion of FOD. 

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

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

Pay attention to the details!

Mar= k S.


On Sat, Apr 11, 2009 at 9:22 PM, Mike Wills <rv-4mike@cox.net> 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 en= gine 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 ove= rall our odds are considerably worse. Comes down to how well an individu= al engineer's his installation and there is a tremendous amount of varia= tion here.
 
The dependence on electronics in the ty= pical rotary install  is a good example. I may be a little sen= sitive to this issue since I've been trying to find an intermittent glit= ch (2 times in 22 hours of engine testing).
 
Mike Wills
RV-4 N144MW  
----- Original Message -----
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 b= een flying my rotary powered RV-6A that the problems have decreased cons= iderably, the success rate and completion rate has gone up and first fli= ghts are now occurring without significant problems =96 even cooling is = OK {:>).  I believe most of this improvement can be attributed t= o folks sharing their knowledge, problems and solutions with others - su= ch as on this list. 

 

I know that fewer parts count is of= ten touted as one of the rotary benefit =96 and while it is true that th= e 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 so= me points and does not have the same inertia loads born by a piston cran= kshaft.  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 t= icking as the old saying goes.  Only extended time and numbers will= provide the true MTBF for the rotary, but I believe it looks very promi= sing.

 

Failure of rotary engines are extre= mely rare, but unfortunately, as with many alternative engine installati= ons, 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 installat= ion successful.  The Canard crowd is fast approaching that status w= ith their somewhat more challenging cooling requirements being over come= .

 

  Having lost a rotor during f= light due to putting in high compression rotors with worn apex seal slot= s worn beyond specs (found this out later =96 my fault for not being awa= re of this spec limit and checking it) which led to apex seal failure an= d 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 flow= ing 14.5 GPH =96 a lot of it undoubtedly  being blown through the d= isabled rotor.  Flew it back 60 miles to a suitable runway and made= a non-eventful landing.   There was a small increase in vibra= tion due to the power strokes no longer being balanced, but nothing bad = and you could still read the needles on the gauges.  Other folks ha= ve had FOD damage to a rotor and also make it to a safe landing.  T= wo folks lost cooling (one loss of coolant fluid , one lost of water pum= p) and while they did cook the engines, both made it back to a safe land= ing.  So all things considered, I think the rotary continues to sho= w that if the installation is designed properly, it makes a very viable = and reliable aircraft power plant.

 

Failure of rotary engines in aircra= ft are extremely rare, but unfortunately, as with many alternative engin= e installations, auxiliary subsystems such as fuel and ignition frequent= ly being one-off designs - have been the cause of most failures.  T= he good news is that for some platforms (such as the RVs) we have pretty= much established what will make an installation successful.  The C= anard crowd is fast approaching that status with their somewhat more cha= llenging cooling requirements being over come.

 

My rotary installation cost me $650= 0 back in 1996, the primary cost being a rebuilt engine $2000 and the PS= RU $2900.  I have since purchased a 1991 turbo block engine from Ja= pan 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 me= rit (or not) in someone=92s mind, the crucial thing (in my opinion) is y= ou need to address two personal factors:

 

1.  What is your risk toleranc= e?  It doesn=92t really matter how sexy some =93exotic=94 engine in= stallation 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 ro= ute.  After all, this is supposed to have an element of fun and enj= oyment to it.

 

2.  What is your knowledge, ex= perience 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 applic= ation to power plant for aircraft.

 

 

Best Regards

 

Ed

 

 

=

From: Rot= ary 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: [F= lyRotary] 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, "par= ts aren't parts" in this case.  Mark was right in that there are ma= ybe 4 "major" components, but you have to define major.  A piston e= ngine 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 probably not.  Is each planet gear in the PSRU a majo= r 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 po= st) it's not that good, but I don't think it has anything to do with rel= iability of the concept.  It's more to do with the experimental nat= ure of the builds and installations.  My original point, perhaps no= t 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..

 

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 bu= ilders and owners.  Not surprising then that almost all ES's have t= raditional 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.  On= e 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 efficienc= y 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 t= o each).  But I stated that as a simple disadvantage - as Mark poin= ted 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 dura= bility advantage.  The total operating cost is certainly significan= tly 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 re= al disadvantage, which I failed to state, is that the extra fuel require= d for a given mission might be 5 or 10% higher and that negated the weig= ht advantage, if only for long-range flights.

 

Is the engine less expensive?  I did a thorough analysis of a di= rect-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? &= nbsp;I'm not sure, but you have to consider the total cost, including en= gineering of all the parts in the system, not just the core engine. &nbs= p;I would love to do a rotary installation, but I don't think I could ju= stify 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.  S= ure, any rotary given sufficient counterbalancing, is perfectly balanced= .  A 4-cylinder opposed recip is not - there is a significant secon= dary couple.  The 6-cylinder opposed engine is perfectly balanced, = but only for PRIMARY and SECONDARY forces and couples - higher order for= ces have never really been analyzed, although they would be very small. =  And then consider the forces within the engine that have to be res= isted by that long, heavy, but flexible crankshaft.  So it isn't th= e mechanical balance that gives the rotary an advantage.  Let's tak= e a look at the the torsional pulsations, comparing the 3-rotor against = the 6-cylinder:  A 6-cylinder engine has 3 power impulses per rotat= ion, as does the 3-rotor, so they are the same, right?  Wrong. &nbs= p;They both incorporate 4 "stroke" cycles, meaning that there separate a= nd sequential intake, compression, power and exhaust events so that is t= he same for both.  The power event, which is the source of the torq= ue impulse, takes 1/2 of a crank rotation for the recip.  In t= he rotary the power event requires 1/4 of a ROTOR rotation, but the roto= r rotates at 1/3 crank rotation - the result is that the power impulse l= asts 3/4 of a CRANK rotation, 50% longer than in a recip.  Therefor= e, the torsional excitation delivered to the propeller, PSRU and to the = airframe is significantly less than for a recip.  And if you analyz= e the actual forces imparted, they go down by the square of the rpm. &nb= sp;The torsional vibration amplitude goes down by a factor of 4 just bec= ause the rpm of the rotary turns about twice as fast.  If you've sk= ipped to the bottom of the paragraph, as you probably should have :-), y= es the rotary is "smoother" - a LOT smoother.. (my apologies to rotary p= urists, 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 eng= ine, but with the high vapor pressure of the fuel - it is more prone to = vapor lock.  The fuel systems of certified aircraft are not particu= larly well designed with regard to vapor lock.  "Fortunately", rota= ry engines typically have no mechanical fuel pump and are forced to rely= on electric pumps.  Fortunately because the pumps can be located a= t the very bottom of the aircraft and close to the fuel tanks, making va= por lock much less likely.  I would caution any builders to conside= r 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 el= ectric pump in the wing root of each wing, feeding the engine directly(t= he check valve in the non-running pump prevents back-feeding).  Red= undancy was by a "crossfeed" line that could connect the tanks together.=

 

And thanks, Mark for - probably incorrectly - referring to me as a "g= ood 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 = :-)

 




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