X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from QMTA04.westchester.pa.mail.comcast.net ([76.96.62.40] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3578329 for flyrotary@lancaironline.net; Sun, 12 Apr 2009 15:57:28 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.40; envelope-from=wschertz@comcast.net Received: from OMTA14.westchester.pa.mail.comcast.net ([76.96.62.60]) by QMTA04.westchester.pa.mail.comcast.net with comcast id egFa1b0071HzFnQ54jwuqg; Sun, 12 Apr 2009 19:56:54 +0000 Received: from WschertzPC ([24.217.81.104]) by OMTA14.westchester.pa.mail.comcast.net with comcast id ejwj1b00F2F2l7c3ajwmnT; Sun, 12 Apr 2009 19:56:52 +0000 Message-ID: <35A283DD76414670B1B480C297514A02@WschertzPC> From: "Bill Schertz" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: forced landings Date: Sun, 12 Apr 2009 14:56:42 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00D2_01C9BB7E.E3F90130" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6001.18000 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 This is a multi-part message in MIME format. ------=_NextPart_000_00D2_01C9BB7E.E3F90130 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable One other thing to watch out for -- This occurred during ground testing, = but if it had happened in the air it would have been a forced landing. From my post of Feb. 8 Well, I haven't heard of this happening before -- I was ground running = my engine to tune it with the EM-2 and EC-2. Ran for almost an hour, = at various rpm's to change the manifold pressure and tweak the settings. = Cooling working well, I had the top cowling off to allow good exit area = since I was tied down. Coolant pressure about 14 psi as reported on the = EM-2. Engine was running good, took it up to ~6000 rpm swinging a 76x76 Catto = prop, when suddenly there was steam and fluid on my windshield. Shut it = down by killing power to the EC-2. Coolant everywhere. Got out and looked to diagnose the problem -- NOT my plumbing. A FREEZE = PLUG in the iron housing had blown out. Rapid coolant dump. Secondary effect -- Since I shut down suddenly from full tilt, either = the proximity of the cowl to the exhaust, or possibly some of the = coolant on the exhaust started a small fire on my cowl. Put it out with = extinguisher, but corner is charred. Now in repair mode. -------------------------- Update since this incident: All freeze plugs (7) on the engine have = been replaced by Bruce Turrentine, and he has inspected the engine. I am = currently reinstalling it and getting ready for more tuning exercises. Bill Schertz KIS Cruiser #4045 N343BS ----- Original Message -----=20 From: Mark Steitle=20 To: Rotary motors in aircraft=20 Sent: Sunday, April 12, 2009 1:51 PM Subject: [FlyRotary] Re: forced landings Charlie, That's a very good point. I'm trying to stay away from assigning a = "cause" for whatever happened because I don't have all the facts. I = have a field that says "Explanation of Failure". Hopefully, we can make = statements as you suggest. Sometimes, even the FAA gets it wrong, like = the time they attributed the engine failure to the builder removing the = oil injection pump. Also, I doubt that we could all agree on a "single = cause" for each failure. Maybe it is due to a poor weld, or wrong = choice of material, or improper strain relief, or lack of heat = shielding, or a little of each. What I hope to accomplish is to point = out areas where we need to be more careful on how we design a particular = part or system. =20 List is at 16 now. Anyone else want to add a "dark and stormy night" = story to the list? =20 Mark =20 On Sun, Apr 12, 2009 at 11:46 AM, Charlie England = wrote: I think that it's just as important to understand the real cause of = the failure. In the case of the plastic fuel flow sensor, it's highly = unlikely that use of the plastic sensor caused the failure; it was the = 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 boating, 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, it failed, but only because of = the wrong application of products, not the products themselves. Charlie -------------------------------------------------------------------------= --- From: al wick To: Rotary motors in aircraft Sent: Sunday, April 12, 2009 10:13:00 AM Subject: [FlyRotary] Re: forced landings Absolutely excellent Mark. I'd encourage you to get the year the = incident occured too. That will be your proof of reduced risk from = things like this newsgroup.=20 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 did precautionary = landing. If you also explain what happened, then a reader can easily = tell you were objective in your rating.=20 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 wild 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 engine 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 improvement. More important than anything. If you can force your self to say: = "That same failure will happen to me". Particularly if you can look at = "contributing 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 to 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 = heat will cause 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....." Every forced landing 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." 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,=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_00D2_01C9BB7E.E3F90130 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
One other thing to watch out for -- = This occurred=20 during ground testing, but if it had happened in the air it would have = been a=20 forced landing.
 
From  my post of Feb. = 8
Well, I haven't heard of this happening = before -- I=20 was ground running my engine to  tune it with the EM-2 and = EC-2.  Ran=20 for almost an hour, at various rpm's to change the manifold pressure and = tweak=20 the settings. Cooling working well, I had the top cowling off to allow = good exit=20 area since I was tied down. Coolant pressure about 14 psi as reported on = the=20 EM-2.
 
Engine was running good, took it up to = ~6000 rpm=20 swinging a 76x76 Catto prop, when suddenly there was steam and fluid on = my=20 windshield. Shut it down by killing power to the EC-2. Coolant=20 everywhere.
 
Got out and looked to diagnose the = problem -- NOT=20 my plumbing.  A FREEZE PLUG in the iron housing had blown out. = Rapid=20 coolant dump.
 
Secondary effect -- Since I shut down = suddenly from=20 full tilt, either the proximity of the cowl to the exhaust, or possibly = some of=20 the coolant on the exhaust started a small fire on my cowl. Put it out = with=20 extinguisher, but corner is charred.
 
Now in repair mode.
 
--------------------------
Update since this incident:  All = freeze plugs=20 (7) on the engine have been replaced by Bruce Turrentine, and he has = inspected=20 the engine. I am currently reinstalling it and getting ready for more = tuning=20 exercises.
 
Bill Schertz
KIS Cruiser #4045
N343BS
----- Original Message -----
From:=20 Mark = Steitle=20
Sent: Sunday, April 12, 2009 = 1:51=20 PM
Subject: [FlyRotary] Re: forced = landings

Charlie,

That's a very good point.  I'm = trying to=20 stay away from assigning a "cause" for whatever happened because I = don't have=20 all the facts.  I have a field that says "Explanation of = Failure". =20 Hopefully, we can make statements as you suggest.  Sometimes, = even the=20 FAA gets it wrong, like the time they attributed the engine failure to = the=20 builder removing the oil injection pump.  Also, I doubt that we = could all=20 agree on a "single cause" for each failure.  Maybe it is due to a = poor=20 weld, or wrong choice of material, or improper strain relief, or lack = of heat=20 shielding, or a little of each.  What I hope to accomplish is to = point=20 out areas where we need to be more careful on how we design a = particular part=20 or system. 

List is at 16 now.  Anyone else want to = add a=20 "dark and stormy night" story to the list? 

Mark =   =20

On Sun, Apr 12, 2009 at 11:46 AM, Charlie = England <ceengland@bellsouth.net>=20 wrote:
I think that it's just as important to understand the real = cause of the=20 failure. In the case of the plastic fuel flow sensor, it's highly = unlikely=20 that use of the plastic sensor caused the failure; it was the use of = plastic=20 in the wrong area without any protection. The homebuilder's = knee-jerk=20 reaction is to say 'no plastic sensors because that one melted', = even though=20 there are tens of thousands of the same sensor in use in boating, a = much=20 more severe environment.

Kind of like the canard builder who = tried to=20 put fuel in a wing built with fuel-soluble foam. Obviously, it = failed, but=20 only because of the wrong application of products, not the products=20 themselves.

Charlie

From: al wick <alwick@juno.com>

To: Rotary=20 motors in aircraft <flyrotary@lancaironline.net>
Sent: Sunday, April 12, 2009 = 10:13:00=20 AM
Subject: = [FlyRotary] Re:=20 forced landings

Absolutely excellent Mark. I'd encourage you to get the year the = incident=20 occured too. That will be your proof of reduced risk from things = like this=20 newsgroup.

Avoid the black and white approach: forced landing or not forced. = Because=20 all things are shades of grey. Instead rate the severity. So it's a = 10 if=20 the guy had to glide, it's a 1 if he did precautionary landing. = If you=20 also explain what happened, then a reader can easily tell you were = objective=20 in your rating.

The final piece is about how many flight hours, first flights = there were.=20 Each year there are more engines flying, so way more likely you will = hear of=20 incident. A wild assed guess is ok, if you just base the guess on = some=20 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=20 each. Even though it's a wild assed guess, it will still be = excellent=20 predictor of change over time. Each year you have the same "error". = So your=20 numbers WILL reflect improvement.

More important than anything. If you can force your self to say: = "That=20 same failure will happen to me". Particularly if you can look at=20 "contributing factors". Then you can dramatically reduce personal = risk. Good=20 example: We had that guy that installed plastic fuel flow sensor in = fuel=20 line. It melted, he died. Tracy just reported hot exhaust caused = fuel to=20 boil out of carb. These have the same root cause. You don't = want to=20 say:" I have efi, can't happen to me". You want to say:" I expect = heat will=20 cause a failure. I'll put a thin ss shield here, with a bit of = fibrefax=20 glued to back. So if muffler fails, it won't affect....."

Every forced landing had 10 little incidents in the past that = preceded=20 it. Your risk isn't some new cause. It's 1 of those 10 incidents = that you=20 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=20 Steitle <msteitle@gmail.com>
To: "Rotary motors in = aircraft"=20 <flyrotary@lancaironline.net>
Subject: = [FlyRotary]=20 Re: Gary Casey was [FlyRotary] Re: Rotary Engines
Date: Sun, 12 = Apr 2009=20 06:45:24 -0500

Mike,

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

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

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

While a = number=20 of these 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 = 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 = engine=20 itself is more fault tolerant than a recip, the peripherals used = in the=20 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=20 experience flying behind the typical LyCon farm implement I think = overall=20 our odds are considerably worse. Comes down to how well an = individual=20 engineer's his installation and there is a tremendous amount of = variation=20 here.
 
The dependence on electronics in = the typical=20 rotary install  is a good example. I may be a = little sensitive=20 to this issue since I've been trying to find an intermittent = glitch (2=20 times in 22 hours of engine testing).
 
Mike Wills
RV-4=20 N144MW  
-----=20 Original Message -----
From:=20 Ed=20 Anderson
To:=20 Rotary motors 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 = problems=20 =96 even cooling is OK {:>).  I believe most of this = improvement=20 can be attributed to folks sharing their knowledge, problems and = solutions with others - such as on this list.  =

 

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 = 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 = 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 saying=20 goes.  Only extended time and numbers will provide the true = MTBF=20 for the rotary, but I believe it looks very = promising.

 

Failure of=20 rotary engines are extremely rare, but unfortunately, as with = many=20 alternative engine installations, auxiliary subsystems such as = fuel and=20 ignition frequently being one-off designs have been the cause of = most=20 failures =96 with probably fuel the prime culprit.  The = good news is=20 that for some platforms (such as the RVs) we have pretty much=20 established what will make an installation successful.  The = Canard=20 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 led=20 to apex seal failure and consequence lost of most of the power = from one=20 rotor, I was still able to maintain 6500 MSL at WOT and fuel = mixture=20 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 = landing.  =20 There was a small increase in vibration due to the power strokes = no=20 longer being balanced, but nothing bad and you could still read = the=20 needles on the gauges.  Other folks have had FOD damage to = a rotor=20 and also make it to a safe landing.  Two folks lost cooling = (one=20 loss of coolant fluid , one lost of water pump) and while they = did cook=20 the engines, both made it back to a safe landing.  So all = things=20 considered, I think the rotary continues to show that if the=20 installation is designed properly, it makes a very viable and = reliable=20 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 as=20 fuel and ignition frequently being one-off designs - have been = the cause=20 of most failures.  The good news is that for some platforms = (such=20 as the RVs) we have pretty much established what will make an=20 installation successful.  The Canard crowd is fast = approaching that=20 status with their somewhat more challenging cooling requirements = being=20 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 a=20 1991 turbo block engine from Japan for $900 and rebuilt it = myself for=20 another $2200.  My radiators (GM evaporator cores) cost = $5.00 from=20 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=20 rotary installation in an RV =96 some folks could do it for = less, some for=20 more.

 

But, = regardless=20 of the technical merit (or not) in someone=92s mind, the crucial = thing (in=20 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 to=20 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 = Casey
Sent: Saturday, April 11, = 2009 8:36=20 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=20 many parts does it take to make a rotary rotate?  Well, = "parts=20 aren't parts" in this case.  Mark was right in that there = are maybe=20 4 "major" components, but you have to define major.  A = piston=20 engine certainly has far more major parts.  Is a valve a = "major"=20 part?  I think so.  Is a rotor corner button a major = part?=20  Not sure, but probably not.  Is each planet gear in = the PSRU=20 a major part?  I say yes, and the PSRU is an integral part = of the=20 rotary engine.  As someone correctly pointed out, it's not = how many=20 parts, but the reliability of the total system that counts. =  Just=20 looking at the history of the rotary (which, from the = implication of=20 another post) it's not that good, but I don't think it has = anything to=20 do with 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 parts=20 is an oversimplification.  But let's face it, to put in an = engine=20 that has had many thousands of identical predecessors is less=20 "experimental" than one that hasn't..

 

Are=20 we ES drivers more conservative?  Probably so, since the ES = is=20 probably one of the experimentals most similar to production = aircraft,=20 and not just because the Columbia (can't force myself to say = Cezzna :-)=20 was a derivative.  Therefore, it tends to attract = conservative=20 builders and owners.  Not surprising then that almost all = ES's have=20 traditional powerplants, with the most excellent exception of = Mark.=20  While there may be more, I know of only two off-airport = landings=20 caused by engine failures in the ES in almost 20 years of = experience.=20  One was caused by fuel starvation right after takeoff = (fatal) and=20 one was caused by a PSRU failure in an auto engine conversion. =  So=20 our 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 = charge=20 can be stratified.  It will probably decrease available = power,=20 though.  I think the best rotary will be 5% less efficient = than the=20 "best" piston engine(same refinements added to each).  But = I stated=20 that as a simple disadvantage - as Mark pointed out, it isn't = that=20 simple.  The rotary already comes configured to run on auto = gas.=20  The piston engine can also be so configured, but the = compression=20 ratio reduction would reduce its BSFC and maybe durability = advantage.=20  The total operating cost is certainly significantly less = if auto=20 gas can always be used to refuel.  I assumed in my = assessment that=20 it will only be available 50% of the time.  The real = disadvantage,=20 which I failed to state, is that the extra fuel required for a = given=20 mission might be 5 or 10% higher and that negated the weight = advantage,=20 if only for long-range flights.

 

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

 

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

 

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

 

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

 

Have a good = day,

Gary

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

 




__________ Information from ESET = NOD32=20 Antivirus, version of virus signature database 3267 (20080714)=20 __________

The message was checked by ESET NOD32=20 Antivirus.

http://www.eset.com/ =


=
------=_NextPart_000_00D2_01C9BB7E.E3F90130--