Mike,
May I suggest adding a coolant level indicator. This will give an early warning in situations like you described. I purchased my float switch from McMaster for less than $30. Be sure to get the high-temp one.
Mark S.
On Mon, Apr 13, 2009 at 7:14 PM, Mike Perry <MKPerry99@cfl.rr.com> wrote:
Here is another to add to the list. "Water pump failure". At 18 hours I noticed my water pump leaking
through the weep hole. This was a slow leak that I would have to add coolant after a two hour test flight.
Since this was the original pump on my 1986 13B I figured it was well past due considering it was 20 years
old. When I bought the new one at the Mazda dealer the parts department said they could only get
rebuilds.
This last Saturday at 72 hours on the engine I took off for my second test flight with a new IVO Magnum
adjustable prop. Excellent acceleration and better rate of climb than my home made composite prop.
However, with the old prop and 2.17:1 PSRU I was never able to get much over 5000 rpm. With the old
prop I would take off and climb to 1000 AGL then reduce power to let temp cool down to below 200 degrees.
It would hit about 220 in the climb. Oil temps have always been below 190.
At medium pitch on the IVO I was close to 6000 rpm and by the time I reached pattern altitude on both
the first and second flights it hit 230. On this second flight I did my usual reduced power and let it cool
down as I flew out to my test area over the sod farms. After 15 minutes of flight time I set power to 5000 rpm
and played with the prop control then worked my way up to 5500 rpm. At this point I am 20 minutes into
the flight when I notice my temps are back at 230. I reduce power to 4000 rpm and check oil temp is
still at 180-190. I turned back to the airport but the temp is still climbing. Reduced power to 3500 and about
90 knots. GPS says 10 minute ETE and now the oil temp is at 200.
I got a straight in to Rwy 33 and when I cut the power on final I had 260 on the water pump outlet sensor,
which was probably just reading hot air and 230 on the pump inlet sensor. Oil temp hit a hi of 230. The engine
never missed a beat the whole time. When I got off the runway and shut it down I had a trail of coolant
behind me. I pulled the cowl off and had coolant all over the bottom cowl where my over flow tube dumps out
but no sign of hose or fitting failures. Sunday after letting it cool overnight I swung the prop through and it still
has good compression from the sound of it. I started to fill up my expansion tank and after about 2 quarts of
coolant I could hear it draining back into my drip pan. The coolant was just running out the weep hole on the
water pump.
I would like to know if anyone else has had problems with water pumps and any comments.
Mike Perry
N981MP
Long Ez
----- Original Message -----
Sent: Monday, April 13, 2009 9:16 AM
Subject: [FlyRotary] Re: forced landings
Dave,
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.
Mark S.
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 <jslade@canardaviation.com> wrote:
Here's a few for the list, Mark,
1. Stock turbo bearings collapsed & took out apex seal. Flew home at reduced power.
2. Fuel filer (sinstered bronze) looked clean but was restricting fuel flow. Flew home on other tank.
3. Bad / intermittent contact on ignition timing sensor made engine run rough. Landed normally and repaired.
4. Turbo hose blew off on take-off. Returned to land at reduced power.
John
------
Been there, done that. (the blown-off intake hose)
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
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.
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.
Thanks Bill,
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.
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 -----
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.
List is at 16 now. Anyone else want to add a "dark and stormy night" story to the list?
Mark
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 <alwick@juno.com>
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.
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.
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.
Subject: [FlyRotary] Re: Gary Casey was [FlyRotary] Re: Rotary Engines
Date: Sun, 12 Apr 2009 06:45:24 -0500
Mike,
Has anyone ever tried to document the rotary incidents resulting in a forced landing?
Here's what I recall from memory, so it likely is missing a few;
3 forced landings due to ruptured oil coolers
1 forced landing due to apex seal coming out of its slot (rotor out of spec)
1 forced landing due to improper assembly of engine (seal wedged 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
1 forced landing on highway due to ingestion of FOD.
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.
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!
Mark S.
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
----- Original Message -----
Sent: Saturday, April 11, 2009 7:31 AM
Subject: [FlyRotary] Gary Casey was [FlyRotary] Re: Rotary Engines
Good analysis and logic, Gary.
You’d make a good addition to the “rotary community”. 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 – 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.
I know that fewer parts count is often touted as one of the rotary benefit – 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 – 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” 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 “gradually and gracefully”, 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 – 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 – 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 – flowing 14.5 GPH – 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 – some folks could do it for less, some for more.
But, regardless of the technical merit (or not) in someone’s mind, the crucial thing (in my opinion) is you need to address two personal factors:
1. What is your risk tolerance? It doesn’t really matter how sexy some “exotic” engine installation may seem – 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’t 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
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!
(do you allow us outsiders in your events? I'll park well away :-)
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