X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from QMTA07.westchester.pa.mail.comcast.net ([76.96.62.64] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3579915 for flyrotary@lancaironline.net; Mon, 13 Apr 2009 18:43:30 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.64; envelope-from=wschertz@comcast.net Received: from OMTA11.westchester.pa.mail.comcast.net ([76.96.62.36]) by QMTA07.westchester.pa.mail.comcast.net with comcast id f30U1b0040mv7h057AiU1t; Mon, 13 Apr 2009 22:42:28 +0000 Received: from WschertzPC ([24.217.81.104]) by OMTA11.westchester.pa.mail.comcast.net with comcast id fAik1b00h2F2l7c3XAinrd; Mon, 13 Apr 2009 22:42:53 +0000 Message-ID: From: "Bill Schertz" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: forced landings Date: Mon, 13 Apr 2009 17:42:43 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0126_01C9BC5F.3FF18E40" 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_0126_01C9BC5F.3FF18E40 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Good concept Mark, the devil is in the details. My incident, which = happened on the ground, would be a Pucker factor of 1 -- however, if it = had happened in the air (anywhere), it would have resulted in an = immediate forced landing, and probably a total rebuild of the engine, = with a PF of 4. It was 'sudden', and 'impressive' with the coolant dump. = =20 SO, a key factor of your table is some narrative of the 'incidents' = impact on flight capabilities of the event. Bill Schertz KIS Cruiser #4045 N343BS ----- Original Message -----=20 From: Mark Steitle=20 To: Rotary motors in aircraft=20 Sent: Monday, April 13, 2009 4:11 PM Subject: [FlyRotary] Re: forced landings Dave,=20 You're definitely in tune with the intent of the database. And I'm = just trying to keep it managable. I will go ahead and include items = discovered during preflight or maintenance which in all probability = would have resulted in an in-flight failure. Those will get a pucker = factor (PF) rating of 1. An example would be Ed's oil pump failure due = to a missing woodruff key. =20 Incidents that happened in flight that resulted in loss of power, but = continued flight was possible, will receive a PF rating of 2. Such as a = turbo hose blowing off. =20 Incidents that happened in the air that resulted in a precautionary = landing will be rated a PF 3. Incidents which happened in the air which necessitated a forced = landing (on or off field) will get a PR of 4. =20 And finally, incidents which resulted in a crash and/or fatality will = be rated PF 5. So, when reporting failures, please provide enough information for me = to determine the proper PF rating. =20 Thanks, Mark =20 On Mon, Apr 13, 2009 at 3:47 PM, David Leonard = wrote: Mark,=20 Thanks for putting together this database. I agree with you and Al = G. that we should keep it to issues with the engine and it's systems. = But I also agree with John and Al W. that we should somewhere include = things that probably would have caused an in-flight failure, especially = when found on pre-flight, run-up or take off roll. That is good stuff. = Not the idiot-pilot-owner stuff like forgetting to attach the return = fuel line, but the alternator bracket and PSRU issues etc - that could = really help someone. Similarly, just because it is in flight does not make it newsworthy. = Like the intake hose blow offs that John and I have both experienced. = Sure, something happened and you are damn sure going to return to the = airport and check it out even though you are pretty sure you know what = happened and it will not affect the safety of flight. OOps, didn't = tighten that hose tight enough. In other words, I think Johns incident #1 is far more significant = than incident #4. Maybe to clarify:=20 #1 caused actual damage to the engine AND he NEEDED to land soon = because of oil loss. Power produced was less than normally aspirated = power. This is an interesting mechanical possibility (that a turbine = blade somehow got BACK into the engine to bust the apex seal) and = something important to consider when designing a turbo install.=20 #4 caused only a reduction to normally aspirated power and a skipped = heart beat or two. No damage, no real need to land other than as a = precaution. No design flaw or mechanical issue - just an = underestimation on how tight to make the hose clamp. (and believe me, = they have to be very tight if there is no bead under the hose.) --=20 David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net On Mon, Apr 13, 2009 at 6:16 AM, Mark Steitle = wrote: Dave,=20 I have decided to take Al's suggestion and limit the criteria for = the spreadsheet to basically include any in-flight system failure which = interrupts the planned flight and results in a premature landing. Based = on this, I will add #3 & #4 as well as the one resulting from a ruptured = coolant hose.=20 Mark S. On Mon, Apr 13, 2009 at 7:55 AM, David Leonard = wrote: Mark, And did you get these? Added by me and John Slade under = the wrong thread title: On Sun, Apr 12, 2009 at 5:15 PM, John Slade = wrote: Here's a few for the list, Mark, 1. Stock turbo bearings collapsed & took out apex seal. Flew = home at reduced power. =20 2. Fuel filer (sinstered bronze) looked clean but was = restricting fuel flow. Flew home on other tank. =20 3. Bad / intermittent contact on ignition timing sensor made = engine run rough. Landed normally and repaired. =20 4. Turbo hose blew off on take-off. Returned to land at reduced = power. John=20 ------=20 =20 Been there, done that. (the blown-off intake hose) =20 Also: I have burned out 2 turbos. The first caused = precautionary/urgent landing at an airport pending shutting off fuel = flow to the turbo. The second, I flipped a turbo oil shut off switch = and flew 1000NM to get home. Had a fuel pump die in flight, switched to the other and kept = flying.(soft failure) I had a bad injector enable switch causing rough running during = some phase one flying (after major change)... landed normally=20 Forgot to re-connect fuel return line in engine bay after doing = some work. dumped a couple gallons of fuel onto the running engine = until I smelled gas and shut down the engine.. (never left the parking = space - but it could have been really bad. Cracked alternator mount bracket found on pre-flight during = phase one testing. Would have lost cooling and alternator if it = happened now. PSRU sun gear pin broke from a backfire during run-up. Was able = to taxi back but would not have been able to fly. =20 This is good - broke a coolant line in flight and smelled = coolant... landed at nearby airport and taxied up to restaurant with = steam spewing out of the cowl. Me and my buddy calmly walked into the = restaurant and had breakfast. Afterward, we borrowed some tools and = fixed the coolant line. Went back into the restaurant to ask for 2 = pitchers of water to put in our plane. Continued ski trip to Mammoth. = The end. --=20 David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net On Sun, Apr 12, 2009 at 2:03 PM, Mark Steitle = wrote: Thanks Bill,=20 With the addition of Bill's exciting adventure, and one of my = own, we're up to 18 incidents in the database. These last two, along = with Ed's brake fire, and an oil coolant rupture, totals four incidents = involving fires during ground operations. Hopefully, everyone carries = at least one fire extinguisher in their airplane. Mark S.=20 On Sun, Apr 12, 2009 at 2:56 PM, Bill Schertz = wrote: 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 =20 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/=20 --=20 David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net ------=_NextPart_000_0126_01C9BC5F.3FF18E40 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Good concept Mark, the devil is in the = details. My=20 incident, which happened on the ground, would be a Pucker factor of 1 -- = however, if it had happened in the air (anywhere), it would have = resulted in an=20 immediate forced landing, and probably a total rebuild of the engine, = with a PF=20 of 4. It was 'sudden', and 'impressive' with the coolant dump. =20
 
SO, a key factor of your table is some = narrative of=20 the 'incidents' impact on flight capabilities of the event.
Bill Schertz
KIS Cruiser #4045
N343BS
----- Original Message -----
From:=20 Mark = Steitle=20
Sent: Monday, April 13, 2009 = 4:11=20 PM
Subject: [FlyRotary] Re: forced = landings

Dave,
 
You're definitely in tune with the intent of the database.  = And I'm=20 just trying to keep it managable.  I will go ahead and = include items=20 discovered during preflight or maintenance which in all = probability would=20 have resulted in an in-flight failure.  Those will = get a=20 pucker factor (PF) rating of 1.  An example would be Ed's = oil pump=20 failure due to a missing woodruff key. 
 
Incidents that happened in flight that resulted in loss=20 of power, but continued flight was = possible, will receive=20 a PF rating of 2.  Such as a turbo hose blowing = off. =20
 
Incidents that happened in the air that resulted in a = precautionary=20 landing will be rated a PF 3.
 
Incidents which happened in the air which necessitated a = forced=20 landing (on or off field) will get a PR of 4. 
 
And finally, incidents which resulted in a crash and/or fatality = will be=20 rated PF 5.
 
So, when reporting failures, please provide enough information = for me to=20 determine the proper PF rating. 
 
Thanks,
Mark
 
On Mon, Apr 13, 2009 at 3:47 PM, David = Leonard <wdleonard@gmail.com> = wrote:
Mark,
 
Thanks for putting together this database.  I agree with = you and=20 Al G. that we should keep it to issues with the engine and it's = systems.  But I also agree with John and Al W. that we should = somewhere=20 include things that probably would have caused an in-flight failure, = especially when found on pre-flight, run-up or take off roll.  = That is=20 good stuff.  Not the idiot-pilot-owner stuff like forgetting to = attach=20 the return fuel line, but the alternator bracket and PSRU issues etc = - that=20 could really help someone.
 
Similarly, just because it is in flight does not make it=20 newsworthy.  Like the intake hose blow offs that John and I = have both=20 experienced.  Sure, something happened and you are damn sure = going to=20 return to the airport and check it out even though you are pretty = sure you=20 know what happened and it will not affect the safety of = flight.  OOps,=20 didn't tighten that hose tight enough.
 
In other words, I think Johns incident #1 is far more = significant than=20 incident #4.
 
Maybe to clarify:
 
#1 caused actual damage to the engine AND he NEEDED to land = soon=20 because of oil loss.  Power produced was less than normally = aspirated=20 power.  This is an interesting mechanical possibility (that a = turbine=20 blade somehow got BACK into the engine to bust the apex seal) and = something=20 important to consider when designing a turbo install. 
 
#4 caused only a reduction to normally aspirated power and = a=20 skipped heart beat or two.  No damage, no real need to land = other than=20 as a precaution.  No design flaw or mechanical issue - just an=20 underestimation on how tight to make the hose clamp. (and believe = me, they=20 have to be very tight if there is no bead under the = hose.)
--=20
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
On Mon, Apr 13, 2009 at 6:16 AM, Mark = Steitle <msteitle@gmail.com> wrote:
Dave,
 
I have decided to take Al's suggestion = and limit the=20 criteria for the spreadsheet to basically include any in-flight = system=20 failure which interrupts the planned flight and results in a = premature=20 landing.  Based on this, I will add #3 & #4 as well as = the=20 one resulting from a ruptured coolant hose. 
 
Mark S.

On Mon, Apr 13, 2009 at 7:55 AM, David = Leonard=20 <wdleonard@gmail.com> wrote:
Mark, And did you get these?  Added by me and John = Slade under=20 the wrong thread title:


On Sun, Apr 12, 2009 at 5:15 PM, John Slade <jslade@canardaviation.com> wrote:

Here's a few for the list, Mark,
1. Stock turbo bearings = collapsed=20 & took out apex seal. Flew home at reduced = power.
 
2.=20 Fuel filer (sinstered bronze) looked clean but was restricting = fuel=20 flow. Flew home on other tank.
 
3. Bad / = intermittent=20 contact on ignition timing sensor made engine run rough. Landed = normally=20 and repaired.
 
4. Turbo hose blew off on take-off. = Returned=20 to land at reduced power.
John =
------ 
 
Been=20 there, done that. (the blown-off intake = hose)
 
Also:

I have burned out 2 turbos.  The first caused=20 precautionary/urgent landing at an airport pending shutting off = fuel=20 flow to the turbo.  The second, I flipped a turbo oil shut = off=20 switch and flew 1000NM to get home.
 
Had a fuel pump die in flight, switched to the other and = kept=20 flying.(soft failure)
I had a bad injector enable switch causing rough running = during=20 some phase one flying (after major change)...  landed=20 normally 

Forgot to re-connect fuel return line in engine bay = after doing=20 some work.  dumped a couple gallons of fuel onto the = running engine=20 until I smelled gas and shut down the engine.. (never left the = parking=20 space - but it could have been really bad.

Cracked alternator mount bracket found on pre-flight = during=20 phase one testing.  Would have lost cooling and alternator = if it=20 happened now.

PSRU sun gear pin broke from a backfire during = run-up. =20 Was able to taxi back but would not have been able to=20 fly.
 
This is good - broke a coolant line in flight = and=20 smelled coolant...  landed at nearby airport and taxied up = to=20 restaurant with steam spewing out of the cowl.  Me and my = buddy=20 calmly walked into the restaurant and had breakfast.  = Afterward, we=20 borrowed some tools and fixed the coolant line.  Went back = into the=20 restaurant to ask for 2 pitchers of water to put in our = plane. =20 Continued ski trip to Mammoth.  The end.

--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net

On Sun, Apr 12, 2009 at 2:03 PM, Mark = Steitle=20 <msteitle@gmail.com> wrote:
Thanks=20 Bill,

With the addition of Bill's exciting adventure, = and one=20 of my own, we're up to 18 incidents in the database.  = These last=20 two, along with Ed's brake fire, and an oil coolant rupture, = totals=20 four incidents involving fires during ground operations.  = Hopefully, everyone carries at least one fire extinguisher in = their=20 airplane.

Mark S.

On Sun, Apr 12, 2009 at 2:56 PM, Bill = Schertz=20 <wschertz@comcast.net> wrote:
One other thing to watch = out for --=20 This occurred during ground testing, but if it had happened = in the=20 air it would have been a forced landing.
 
From  my post of Feb.=20 8
Well, I haven't heard of = this happening=20 before -- I was ground running my engine to  tune it = with the=20 EM-2 and EC-2.  Ran for almost an hour, at various = rpm's to=20 change the manifold pressure and tweak the settings. Cooling = working=20 well, I had the top cowling off to allow good exit area = since I was=20 tied down. Coolant pressure about 14 psi as reported on the=20 EM-2.
 
Engine was running good, = took it up to=20 ~6000 rpm swinging a 76x76 Catto prop, when suddenly there = was steam=20 and fluid on my windshield. Shut it down by killing power to = the=20 EC-2. Coolant everywhere.
 
Got out and looked to = diagnose the=20 problem -- NOT my plumbing.  A FREEZE PLUG in the iron = housing=20 had blown out. Rapid coolant dump.
 
Secondary effect -- Since I = shut down=20 suddenly from full tilt, either the proximity of the cowl to = the=20 exhaust, or possibly some of the coolant on the exhaust = started a=20 small fire on my cowl. Put it out with extinguisher, but = corner is=20 charred.
 
Now in repair = mode.
 
--------------------------
Update since this = incident:  All=20 freeze plugs (7) on the engine have been replaced by Bruce=20 Turrentine, and he has inspected the engine. I am currently=20 reinstalling it and getting ready for more tuning=20 exercises.
 
Bill Schertz
KIS Cruiser = #4045
N343BS
-----=20 Original Message -----
From:=20 Mark Steitle
Sent:=20 Sunday, April 12, 2009 1:51 PM
Subject:=20 [FlyRotary] Re: forced landings

Charlie,

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

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

Mark   

On Sun, Apr 12, 2009 at 11:46 AM, = Charlie=20 England <ceengland@bellsouth.net> = wrote:
I think that it's just as important to understand = the real=20 cause of the failure. In the case of the plastic fuel = flow=20 sensor, it's highly unlikely that use of the plastic = sensor=20 caused the failure; it was the use of plastic in the = wrong area=20 without any protection. The homebuilder's knee-jerk = reaction is=20 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 more severe environment.

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

Charlie

From: al = wick=20 <alwick@juno.com>=20

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

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

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

The final piece is about how many flight hours, first = flights=20 there were. Each year there are more engines flying, so = way more=20 likely you will hear of incident. A wild assed guess is = ok, if=20 you just base the guess on some facts. For example, you = could=20 check faa database and find 100 planes registered with = rotary=20 engine in 2005. You can guess that equals 70 hours each. = Even=20 though it's a wild assed guess, it will still be = excellent=20 predictor of change over time. Each year you have the = same=20 "error". So your numbers WILL reflect improvement.

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

Every forced landing had 10 little incidents in the = past that=20 preceded it. Your risk isn't some new cause. It's 1 of = those 10=20 incidents that you rationalized away, instead of = saying:" that=20 will happen to me too."

Good stuff.


-al wick
Cozy IV with 3.0 liter Subaru
230+ = hrs tt=20 from Portland, Oregon

---------- Original Message = ----------
From: Mark Steitle <msteitle@gmail.com>
To: = "Rotary motors=20 in aircraft" <flyrotary@lancaironline.net>
Subject:=20 [FlyRotary] Re: Gary Casey was [FlyRotary] Re: Rotary=20 Engines
Date: Sun, 12 Apr 2009 06:45:24 = -0500

Mike,=20

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

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

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

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

Pay attention = to the=20 details!

Mark S.


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

Good=20 analysis and logic, Gary.

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

 

Best=20 Regards

 

Ed

 

 

Ed=20 Anderson

Rv-6A=20 N494BW 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: = Rotary motors=20 in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of = Gary=20 Casey
Sent:=20 Saturday, April 11, 2009 8:36 AM
To: Rotary = motors in=20 aircraft
Subject: = [FlyRotary]=20 Re: Rotary Engines

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

Have a good=20 day,

Gary

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

 




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The message was checked = by ESET=20 NOD32 Antivirus.

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<= /BLOCKQUOTE>


--
David Leonard

Turbo Rotary RV-6 = N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
<= /DIV>



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