Mistral Rotary

[aadamson]

Bitsko,
Most piston engines won't even run there, or are very rough. Mazda couldn't run that lean in a car due to Nitrous oxide emmissions.

My opinion only,
Bill Jepson

Bill, I hope you meant to say "carbon monoxide" emmissions? If it were realy NOS, you'd be plumbing it back into the intake and making even more power.... NOS is a really good oxidizer that burns really fast and they use in racing engines..... Or of course, at your dentist office


Couldn't resist, but I suspect that should have been Carbon Monoxide.... But then again, we all want to know what you were *breathing* and we'll take some!

 

[Yukon]

Van's Integrity

Bitsko,
Don't worry terribly about rotary fuel burn. Several reasons why, 1) Mazda must set up the car engines for a very wide dynamic range. Almost all mods done to recent 13B and Renesis engines are to make the engine torque available at low RPM. We don't need low RPM except for idle. Lean of peak operations have proven to be excellent on the rotary. We're not talking 50? here either. Tracy Crook has been regularly running almost 200?F lean of peak! Most piston engines won't even run there, or are very rough. Mazda couldn't run that lean in a car due to Nitrous oxide emmissions. Mistral has shown O-360 or better levels comparing their N/A 190 HP version.
Lastly, the fuel burns shown in the Sport Avation article are pure BS. The article was posted first in the RVator newsletter, after which several items were posted about the test methods. The test was set-up at the Lyc's best cruise RPM. There wasn't time enough to find the rotaries best fuel burn RPM. Since Van is a Lyc engine sales outlet, have a Van's employee write the article smacks of conflict of interest to me.
My opinion only,
Bill Jepson

Bill,

That's a little hard to take! I've never seen anything come out of Van's that wasn't factual. With 95% of the RV market, Lycoming doesn't need any unfair advantages. They fueled those airplanes before and after the test missions, and the fuel used by each airplane was printed. Not much of a chance to influence those numbers either way. If the rotary guy's didn't think the flight profiles were fair, they would have spoken up in advance.

All engines designs have shortcomings, and from everything I have seen, including the Van's tests, the rotary suffers from higher fuel consumption.
To deny it would be like Egg saying that his engines weigh the same as Lycs,
while his builders keep ballasting their tails.

John

 

[rv6ejguy]

The lowest AVERAGE emissions of HC and CO occur at stoichiometry (peak EGT). The highest oxides of nitrogen occur there unfortunately also. These are all dealt with by the cat in automotive use (reducing and oxidizing) to emit mainly CO2 and water vapor. As we lean further, NOx fall off due to lower EGTs. The modern 3 way cat technology is so good now that all three major pollutants are almost nil on 2006 cars. Since we are not concerned about emissions in aircraft, this is all a moot point. We try to cruise for maximum MPG and we don't have cats on aircraft.

My opinion about the Powersport flyoff at Van's was that this was carried out with the truth in mind and fairly scientifically. With tanks filled before and after each flight, total fuel burn for each mission was established. I think Van's is genuinely interested in alternative engines at least from a technical curiosity perspective.

What should be remembered is that this is just one (two) Wankel setup(s) and we have no idea how the ECUs were programmed on these engines. To say that all Wankels will burn more fuel in this application is premature as others have posted comparable burns to Lycos when properly leaned. I have an open mind on these claims and would like to see someone like Tracy Crook or Mistral or a newer H6 Egg do a fly off at Van's. I certainly don't believe a lot of what I read on the web about engine performance. Mistral seems like a solid company with intents to certify their engine. It is important for any company in this field to submit their engine installation for independent testing when it is fully developed to verify their claims.

The recent flyoff between an Eggenfellner powered 9 against Van's Lyco 9 showed that it was not quite equal in performance but close in overall fuel burn. I agree to some point that different engine/ prop combos may not show the same efficiencies at identical altitudes, speeds and power settings however max cruise at 8,000 feet, max climb rate and total mission fuel burn give a good picture of total performance of each combo.

Without a full CAFE type test on each combo to compare the entire spectrum of performance, the Van's method and open invitation to auto conversion flyoffs seems the next best way to compare. I applaud Van's for showing an open mind and taking time out to supply aircraft and pilots to do these tests. They really don't have any vested interest other than curiosity as they are solidly in the Lyco camp. They simply say- show up with what you've got and we'll listen.

 

[gmcjetpilot]

Man on the grassy noll

Bitsko, Don't worry terribly about rotary fuel burn. Van's employee write the article smacks of conflict of interest to me. My opinion only, Bill Jepson

Bill there's no conspiracy. There are real physical reasons that a Wankel engine will always have two hard to overcome issues, spacific fuel consumption and noise. It's the shape of the combustion chamber and speed of the exhaust. The side by side fly off Ken came up with was fair.

I do get your point about how a rotary engine can fly really leaned and yada yada yada. This may be true, but you will now go way slower. It's the "no free lunch thing" and "you can't have your cake and eat it to" deal.

Clearly the rotary engine is a wonderful thing and Dr. Wankel was brilliant. You can't take that away, and no wounder there is a fascination with its "smooth" power. However this does not mean the reciprocating 4-stroke engine does not have it's own advantages, one of them being better spacific fuel consumption. Also a well balanced Lyc can be pretty smooth. Of course the air-cooled Lyc also has the advantage of less weight and cooling drag.

The auto market has spoken. Mazda is the only major manufacturer of Wankel engines. Does that make the RX-8 sports car bad? No, of course not. My Mom an Dad owned a RX-2 and RX-3 in the 70's. They where fun to drive.

Is the Mazda RX-8 ECU's optimal? Than why is the gas milage less (18/24 mpg city/hwy) verses comparable HP sport cars (23/31 mpg city/hwy)? There is only so much leaning you can do. The Nissan 350Z has the same gas milage as the RX-8, but the piston engined 350Z has about 85 more HP.

Van does not make that much money selling Lycomings. The Flt test was good, and spoke well for the rotary. Performance was on Par, weight was not way out of line and looks I think are cool. The down side is they are expensive and this Wankel kit engine is not currently available.


How can a Lycoming design, dating back into the 40's and 50's, out perform a "modern" engine? How can that be? I have heard all the enthusiastic hype and rhetoric for Wankel engines and all the Lyc bashing. It's hard to justify test results when you think the Lyc is dated.

You have a choice, you can make excuses or say, hey, the Lyc is a very good engine for aircraft. That does not take anything away from the coolness of a Wankel, but the Wankel is not a quantum leap in performance or efficency some dream of. It's differnt, that's it.

To over come noise, mufflers can be added but at the expense of cost, drag and weight. As far as fuel consumption, a turbocharger can achieve good fuel numbers if flown at high altitudes, but again this adds weight, cost and complexity. It's all trade off. I personally don't want to just fly at O2 mask altitudes to take advantage of a turbo.

I suppose the test could have been done with a turbo Wankel leaned out against an Atmo Lyc at 12,500 feet. That would level the playing field. The Wankel would likely be as fast with similar fuel burn or faster with more burn.

It's the turbocharger that improves the efficency. Of course all bets off if the Lyc is also turbo-ed and inter-cooled. Than you would see similar results as you see at sea level. You can play this game all day. I don't enjoy flying at 12k and get a headache without O2. However if all you want is to cruise at +12.5k with a gas mask, than a turbo Wankel may be the way to go.

For me the final straw is the fuel oil mixing with the Wankel. That's a pain I don't want, but I am told it's no big deal. I just don't want to deal with it. If you leave the oil injector on it adds weight.

Hummm may be those old Lycoming engineers in the 20th century knew something? The question is how can a rotary be made, lighter, quieter, more fuel efficient w/ less cooling drag. I hear about ECU programing but you need fuel to make power. I have heard about doing this and that it will make it better. True but lets "get it ON" and find out.

 

[Bitsko]

I can see a POTENTIAL conflict of interests with a Lycoming dealer, but everything Vans says about the issue makes sense. Like I've said, I have no beef with Lycomings or their fans. I just like to experiment, if I can find a way to do so without killing myself.

The Powersport setup is very interesting. Mistral's approach to redundency is to have "2 of everything" running both rotors. Powersport's approach, with separate systems for each rotor, basically gives you 2 separate engines in a single case, sharing only the crank. (Which, in a rotary, is almost completely immune to failure. They're unbelievably tough.)

A mechanically-challenged friend of mine used to drive an old RX-3 in high school. One day he asked me why it kept "seizing up" periodically, and then running again after it cooled down. The answer was simple: The oil pan was bone dry. He had been running it for the better part of a year with NO OIL whatsoever. Not even a decent amount of sludge. It would heat up and seize, but sure enough it would fire right up when it cooled down. Unbelievable. The same idiot bought a new '83 RX-7 when he graduated. He was showing off the top speed one day, when he remembered that he'd "heard somewhere" that they were faster in 4th gear instead of 5th. He downshifted, popped the clutch, and literally dragged the rear wheels at well over 100 mph as the tach spun past the peg. Didn't bother the engine a bit. (Ruined my undies, though.)

I think the chances of a sudden MECHANICAL failure in a well-built rotary are practically nil. They're rare in Lycomings, but they happen. You simply can't blow up a rotary.

Fuel economy is a concern, but it has to be considered in light of total operating costs. A Powersport, complete with all accessories and engine controls, is far cheaper than a bare Lycoming or clone. Rebuild costs are certainly going to be a lot cheaper, too. All those thousands of dollars will buy a lot of fuel.

If I go that route, I'd have separate EVERYTHING: Batteries, power busses, harnesses, etc. But I'd do that regardless of engine choices.

 

[cjensen]

You simply can't blow up a rotary.

This is simply not true. It has happened, and it ain't pretty when they let go. I LOVE rotary engines. I have one that I've torn down, and it's a marvel of technology. I'm not using one, but I love the engine.

A Powersport, complete with all accessories and engine controls, is far cheaper than a bare Lycoming or clone.

This is not true either. Trust me, I've tried my hardest to justify the Powersport package back when I WAS planning on using a rotary. I've talked to Ray numerous times, and the engine with all accessories, controls, FWF stuff is not cheaper. I'm swallowing a whole bunch of other defensive posts on alternative engines by saying this as well, but any FWF package other than a homegrown install, is more expensive than the clone counterpart. I've run the numbers for over six months time and again, comparing apples to apples, and the alternatives are ALWAYS more expensive to get installed and running with a prop out front.

Yes, I've eaten my words, and seen the light after dealing with several of the alternative engine guru's. I now feel that you can't beat the Lyc's or clones YET. It may happen, but we aren't there yet.

(If you read this...Sorry Ben!)

 

[RVbySDI]

This is simply not true. It has happened, and it ain't pretty when they let go. I LOVE rotary engines. I have one that I've torn down, and it's a marvel of technology. I'm not using one, but I love the engine.


This is not true either. Trust me, I've tried my hardest to justify the Powersport package back when I WAS planning on using a rotary. I've talked to Ray numerous times, and the engine with all accessories, controls, FWF stuff is not cheaper. I'm swallowing a whole bunch of other defensive posts on alternative engines by saying this as well, but any FWF package other than a homegrown install, is more expensive than the clone counterpart. I've run the numbers for over six months time and again, comparing apples to apples, and the alternatives are ALWAYS more expensive to get installed and running with a prop out front.

Yes, I've eaten my words, and seen the light after dealing with several of the alternative engine guru's. I now feel that you can't beat the Lyc's or clones YET. It may happen, but we aren't there yet.

(If you read this...Sorry Ben!)

Chad, I am right there with you on this topic. I am also trying to justify the costs of installing an alternative engine in my RV. With the prices these alternative "guru's" are charging, the truth is that the Lyclones price is still cheaper (although I still contend is very much over priced). It looks like it will be this way as long as everyone is convinced that an airplane engine just has to cost what it does to pay for the research, the certification, the yada yada yada. More and more it looks like I have to resign myself to the fact that if I want to get an engine in my plane the best cost alternative is the Lyclone. I don't feel it is the best choice in terms of technology, efficiency, performance but it is turning out to be the best in price (as sad as that is to think about when saying that we are talking about an engine that costs $20,000 - $30,000 + to buy).

 

[Bitsko]

I hope things are different when I reach that point.

Anyway, here is a year-old bit of info from www.rotarynews.com

http://www.avweb.com/news/columns/189247-1.html

A Return to the Rotary
by Marc Cook

Recently, I received a note from Francois Badoux from Mistral Engines, the company working hard to get a Mazda-based, two-rotor Wankel into aircraft. I expressed my skepticism that a rotary could be made as fuel-efficient as a piston engine. I recall well how hard Mazda worked to improve efficiency in its cars, and had the great pleasure of running a '93 RX-7 down to about 10 mpg on some, er, spirited driving.

I was delighted to discover that Badoux was not writing to call me an idiot -- always a nice change of pace -- but to inform me that his engineers have made great progress. "Mistral Engines' engineers struggled to reach this result but we can now announce it: We have as good or better fuel consumption than comparable-power Lycoming and Continental models. We are getting 0.46 pounds per hour per hp (lb/hr/hp) at 75-80% cruise settings (on 87-octane mogas) on our normally aspirated G-190 model. We are still working to optimize the exhaust manifold. I keep a bottle of champagne in the fridge for the day my guys get 200 hp!"

He included a chart that showed the G-190 delivering the 0.46 at 150 hp, and slightly less than that (say 0.47) at 75%.

The trick? "We achieved this through lengthy optimization of parameters such as the intake manifold, tuning the intake runners, careful positioning and choice of the injectors, etc. But first and foremost, we have developed (to the latest FAA certification standards) an extremely versatile and capable Digital Engine Management (DEM) system that allows us to optimize every engine parameter on a per-revolution basis. It is the key to getting good efficiency out of the rotary which, as you well know, has an inherent disadvantage on this dimension due to the unfavorable volume/wall surface ratio of its combustion chambers." Wait, that's not the whole trick. This sophisticated engine-management system runs the little rotary lean of peak EGT right up to 85% power. There are significant gains to be had. Normal takeoff fuel flow is 18.7 gph, but, running LOP at 75% power the flow is 10.9 gph -- right in there with a standard IO-360 Lycoming running rich of peak.

Yes, I know that you can take that same Lycoming, balance the fuel flows, and run it LOP, too, for the same kind of savings. And, yes, you could get the piston engine to run with greater efficiency than the rotary. But the point is that Mistral is close, amazingly close, to closing the efficiency gap, at which point it can start standing up and talking about the benefits of the little engine. Hint: No exhaust valves to burn, extremely smooth running, beer-keg size.

What tickles me about the Mistral development is that the engineers have edged up to excellent efficiency not just by good design and high-end electronics, but by making lean-of-peak operations routine, indeed probably mandatory.

How refreshing is that?

February of '05. If Mistral is to be believed, they've already sold some 190 hp engines, as well as 230 hp turbos. As others have pointed out, the turbo will probably be the most competitive IF you have need for a high-altitude engine. I live out West, and flying over 12,000 foot peaks is going to be necessary if I want to make a beeline somewhere. The turbo's capabilities turn me on. A turbocharged Lycoming is a quantum leap upward in cost, and I think the Mistral will probably compete favorably in that area.

 

[Bitsko]

In trying to compare apples to apples, I'm assuming comparably-equipped engines on both sides of the equation. That means a Lycoming has to be FADEC-equipped to make the comparison a fair one. Just going by current web site numbers (by no means 100% accurate, but probably in the neighborhood) I compared a decked-out Aerosport "Lycoming", a turbo Mistral and an Egg-aru:

Aerosport IO-360 B1B: $24,400
Reiff pre-heat: 525
80-amp alt: 325
High-torque starter option: 100
high-comp pistons: 300
port & flow match: 500
boost pump & filter: 520
Whirlwind "RV" prop: 7500
Jihostroj governor: 1275
FADEC: 7175
Cockpit kit (for FADEC): 1403

Total: $44,023

New Eggaru Turbo H6: $28,800
4-blade C/S prop: $9900
Prop gov: 595
110A alt option: 500
EIS monitor: 1500
Heater kit: 600
Muffler: 700
filter: 200

Total: $44,090

Mistral 230 hp turbo: $36,000 (includes FADEC and all accessories and controls.)
MT 3-blade prop: 8060
governor: 1275

Total: $45,335

The Eggaru and the Mistral make more power, and are both turbocharged. The price of all three packages are pretty comparable. Add a turbo to the Aerosport, though, and the price would go through the roof.

I realize these are all high-end setups, and that a LOT of money could be saved on a used Lycoming with traditional carb and mags. There is no question that's the way to go if you're pinching pennies. Realistically, I'll probably end up pinching pennies. But since I'm just dreaming my little dreamy-dreams at this point, I can afford to spend imaginary money. Seems to me that if you compare all 3 engines with comparable technology, the price is going to be almost identical. The turbos would be the high-altititude performanc winners. Long term costs? Who knows?

 

[gmcjetpilot]

The numbers

Here are some numbers I got off the Powersport and Mattituck web site.

Powersport
RE-215 215 Horsepower Rotary Engine, reduction drive (less exhaust)
$ 24,000.00
PSRU-300 2.29-1 Propeller Speed Reduction Drive only
$6,500.00

Assume the cowl and engine mount are a wash with a Van trade-in.
The outright cost of the cowl is $900.00 , engine mount about $1,400

Oil Cooler oil to water cooler or oil to air cooler- $590.00
Radiator Custom Aluminum Radiator - $580.00
Exhaust Stainless Steel Exhaust With Silencer - $2,500.00
Engine mounts set of 3 CNC Machined Aluminum Engine Mounts - $600.00
Vibration Isolators set of 3 Barry Controls Oval Vibration Isolators - $950.00

Total Airframe Installation kit (w/o engine mount and cowl)
$5,220.00

Engine Total is $35,720.

Add a MT elect prop about $8,740 you are up
Total $44,460

Lyc clone
A 180 HP IO-360 c/s $22,200
Vans installation kit $4,800,
Hartzell $5,880
Total $32,880

The difference $11,580

If you base it on Lyc IO-360 200HP the Powersport is about the same. However I think the power of the Powersport is closer to the performance of a 180HP Lyc. Of course you can save money with a Carb and Fixed pitch prop and still have similar performance. Clearly a homegrown Rotary, aka RWS - Real World Solution, with a garage rebuild of a junkyard rotary engine will save lots of money. However you can bargain hunt a used Lyc and overhaul it yourself as well. I think Tracy Crook of RWS has a great line of products, but I also think the powersport B13B will produce better performance than a typical homegrown 13B engine from RWS parts. Of course the Mistral is more money than the powersport. The dollar value Bitsko posted for the Mistral above, I don't believe includes installation parts.

 

[Bitsko]

That's why I equipped my imaginary Lycoming the way I did: FADEC, etc. The other two have it, so I have to put it on the Lycoming for the comparison to be fair.

There is no question that a Lycoming could be installed for a fraction of the cost of the other two, but you have to give up a lot. By the same token, I could take a greasy old Subaru engine out of a junkyard donor for $100, stick a used PSRU on it for a thousand bucks, and be in the air for a lot less than a halfway decent used Lycoming. But that would be an absurd comparison.

Those of us who are interested in "alternative" engines tend to also be interested in fuel injection and modern electronic engine controls. You can't compare these engines against a Lyc unless you level the playing field. If I didn't want FADEC and all the other amenities I'd obviously get a Lycoming. No question. But all "decked out" as I've described, it's more a matter of personal preference. Rational arguments can be made either way.

This is the "Alternative Engines" section, after all. I don't think there is anybody paying regular attention to this section that isn't aware of all the pro-Lycoming arguments...and probably agrees with them, too. I'm sure Orville and Wilbur had no objections to horses, generally speaking. But they insisted on flying anyway.

If there are ever going to be better alternatives to Lycomings then SOMEBODY has to experiment. A better mousetrap is of no value if nobody ever buys one.

p.s. I made the prop choices I did because of my general "I don't want to think about it" philosophy. A Hartzell-Lycoming combination has speed restrictions due to vibration. I've equipped my imaginary engines with composite props that have no restrictions. I think the fewer such items a pilot has to worry about, the more attention he can give to OTHER things. A Hartzell obviously saves money....but ruins the "apples-to-apples" comparison.

 

[cjensen]

I'm sure Orville and Wilbur had no objections to horses, generally speaking. But they insisted on flying anyway.

Now THAT'S a funny comparison!

 

[Bitsko]

Thanks.

If we were practical people we wouldn't be interested in flying at all. Believe me, I've tried to justify this New Mania every way I can think of. "The kids will learn about physics and mechanics." "We can fly to (wherever) whenever we want to." Etc, etc. But I'm full of B.S. and I know it.

My family calls me "Mister Toad" when I get these notions into my head. That's fair enough. I'm done trying to justify it. In fact, I've already got my nose art picked out:

I've gone through the "Custom Les Paul" mania, the "old British sports cars" mania and the "Let's adopt Russian orphans" mania. (The last is currently eating me out of house and home. I've never seen people consume so much sour cream.) And, like Toadie, when I go nuts I go ALL THE WAY nuts.

 

[Bitsko]

I like your website, Chad. Your home reminds me of my own suburban idyll. If you can build a plane in YOUR garage, then I can pull it off too.

The empennage kit spread out on the bedroom floor reminds me of the time I rebuilt an NP-435 transmission for my Bronco on the kitchen floor. (About 2 manias ago.)

Your engine wish-list resembles mine, except that I've pretty much chucked the Innodyn idea. I think it's snake oil. (Though I watch their online flight testing videos with the sound turned up whenever I need a good time. They almost qualify as porn.)

 

[cjensen]

Thanks Bitsko!

Funny you mentioned the Innodyn video...I hadn't watched it for a good month or so, and just this morning, watched it again.

 

[N713R]

Using a Mazda

I can tell you first hand, if you are looking for price, go with a Lyclone. I am building my own Mazda FWF. I have used RWS for the engine controller and the redrive, Bruce Turrentine engine, and Conversion Concepts mount, but have made or designed most of the rest myself. I am trying to do it right, and use good quality parts in the package. I will have quite a bit in it when I get done. I will not however have as much money in it as I would if I had bought a Lyclone, but I am not far away, not to mention that I have an extra year in the development of the package, and I am just now getting ready to start it for the first time. As a side note, there are guys that have done it for far less money than my install, and not taking anything away from them, but they are using alot of hardware store and junk yard components. I want an install that has the best available components to me at the time of build, and I want an install I can take the cowling off on the flight line, and be proud to show what I have done. I will attach the most current picture I have without having to go to the hanger to get my camera.

http://img206.imageshack.us/img206/2551/p00009743zw.jpg
http://img206.imageshack.us/img206/8153/p00009720lz.jpg

Bottom line, do not install the rotary for $$ savings, and do not install the rotary if you are worried about pennies of operation cost. I know I will burn more fuel, and I don't care. I am doing this because I believe the rotary has promise for the future, and I like the problem solving involved in the install. Plus, it is something different, and I like that. The rotary (at its current state) is for the true experimenter that plans to tinker for years to come. If you want a hop in and fly airplane, stick with the Lycs.

Above info worth exactly what you paid for it!

 

[rv6ejguy]

Power to you Ben! You sum up my thoughts on alternative engines pretty well. If we all wanted a Lyco, we wouldn't be here discussing alternatives, we'd be getting out our checkbooks.

 

[cobra]

Ben,
Nice intake- make it yourself?

Im going rotary for lots of reasons- the biggest is because it is as reliable and safe as a non-turbine engine can be. Other important reasons are smoothness, simplicity, water cooling, ease of maintenance and overhaul, low cost, high power to weight, linear torque/hp curve (extremely flexible operating envelope) with much bigger power upside than similiar Lycs, loves mogas, loves turbocharging, low internal stresses/does not wear. Does not break crankshafts and has no exhaust valves. Seldom stops catastrophically like piston engines can and do when parts break. Weight and fuel economy are very close at any comparable HP level below 180HP (can take leaner mixtures w/ cast iron rotor, less detonation potential), significantly better power:weight above that level.

The only potential downside is the ease of installation/time difference (not a big deal imho- it is easy to copy/improve working setups on cooling and exhaust systems, mounts, etc). T Crook provides most of the conversion parts needed. CS prop selection might be more limited, but the lightweight (cheap) composite IVO magnum adjustable prop looks to be a likely prospect for a Rotary (not for Lycs) on a 9A. The faster planes will probably need to stay with the more expensive MT. believe the rotary is probably a better match for fixed props, simply because higher rpm operation is easy and safe.

BTW George, your Lyc probably uses more oil than a Mazda does, even with the Rotary's oil injection cooling.

 

[N713R]

Intake

Mike,

Yes, I made the intake. However, I did not weld it. I designed and built it, and had professional welder weld it up for me. Same welder also made my radiator, and oil cooler. After we sat down together and figured out area and placement. Welding is one aspect of this that I am not taking on myself. I can weld, but not well enough to weld on my airplane, and not well enough to look as nice as I want it. So I have opted to pay for that.

 

[gmcjetpilot]

We agree to disagree

Im going rotary for lots of reasons- reliable, safe, smoothness, simplicity, water cooling, ease of maintenance, and overhaul, low cost, high power to weight, linear torque/hp curve, loves mogas, loves turbocharging, low internal stresses, no crankshafts, no exhaust valves, seldom stops catastrophically, Weight, fuel economy close, significantly better power weight

BTW George, your Lyc probably uses more oil than a Mazda does, even with the Rotary's oil injection cooling.

We can agree to disagree. Items you think are a positive I think are negatives. Dr. Wankel was a genius, no doubt. Wankel engines are a wonder. However attributes you claim don't pan out in the real world. The reasons N713R has are right on.

I think the Lyc has the advantage over the Mazda 13B:

-Power / weight (installed) (RV's with Lycs weight less and go faster)
-Fuel economy (Mazda RX8 - 18mpg, every other 220HP sports car 23 mpg)
-Maintenance (no fiddling with support systems, cooling, ECU, O2 sensor)
-Reliability (no water cooling, no electrical dependence, lower stressed engine)
-Drag, less drag, abundance of cooling AIR for AIR cooled engine.
-Cost (Cheaper to purchase and operate)
-Cranks, Linear torque curves, valves, turbos, mogas and so on (could care less)
-Exhaust Sound, Not the high pitch scream of 100 chain saws.
-Smooth myth - A well tuned Lyc with a balanced prop is very smooth.
(Put a wood prop on a Lyc it is "turbine" smooth. My point is
it's subjective and not a big deal to me. Lycs are smooth enough.)​

Wankel's burn more gas, period and always will. Sorry the truth has to be told, no excuses. That is OK but you have to accept it.

As far as power what counts is what is at the prop. If the Wankel was so powerful I wounder why RWS Tracy runs his RV-4 in the 160HP class? The Powersport is a highly modified 13B making more HP than a stock 13B. It matched a 180HP Lyc (at huge fuel penalty).

Weight; Get the scales out. RV's with alternative engines weight more. The powersport is one of the lightest rotary installations and still was on par with a heavy angle valve 200HP Lyc. Again no big deal but a reality.


I DON'T BUY YOUR "significantly better power weight" and "fuel economy close" COMMENTS AT ALL.

Internal stresses; There are huge stresses in a Wankel. The rhetoric always comes back to some comment of Lyc crank shafts and so on. Think about a 1.3 liter Wankel winding up high RPM's trying make as much power as the slow turning Lyc with a 5.9 liter displacement! You know how de-tuned that is. A car engine of this size can make 700 HP or more, easy. Now that is low stress. The Lyc is not breathing hard. Structurally the Lyc has rods and cranks like I-beams off the Golden gate bridge. Failure per hour flown is low. The crank AD's are pure sub-manufacturing mess up. The Lyc can be ran at 100% power all day and be rebuilt many times after going to a 2000 hr TBO. Component fatigue life in the 10's of thousands of hours.

I have been around Wankel's since the mid 70's and they EAT parts all the time. I worry more about the ECU, water pump, hoses and radiator more than a crankshaft. A hot Wankel will cook itself to death, but a Wankel will more likely stop because the ECU or electric fuel pump took a dump. It may be unlikely but it can happen just like a crank failure.

Oil USE - I asked Tracy and another famous well known Wankel'ers about their oil use. It's over twice an average Lyc. The bottom line is I can fly my Lyc several gas fill-ups, two or three times with out breaking out an oil jug. A Wankel, with oil in the gas tanks, is an every fill up deal. Hey I just don't like it. I like my oil in the crank case, not in my fuel tanks. An injector pump is another thing to fail. I suspect most leave the pump off for weight. We can agree to disagree and wish you all the best with your project.

 

[Yukon]

Inexperience

One reason for my "experimental" mindset is a total lack of experience. I'm taking flying lessons specifically to justify building a kitplane. I'm learning EVERYTHING from the get-go. Therefore, I have no built-in biases either for or against any particular engine. But I also have to be cautious not to jump on any bandwagons based on what a web site has to say. (*cough* INNODYN *cough* *cough*......)

Right now, the frontrunners are a Lycoming clone and the Mistral rotary. I think the rotary's fuel economy will end up being the biggest sticking point. I don't doubt that an electronically-controlled Mistral will compare well with a carb-and-mag Lycoming, but when you add FADEC to the Lycoming I think all bets are off. At the end of the day, all other things being equal, you simply cannot get the same fuel economy from a Wankel engine as you can from a piston engine. If Mazda can't do it with all their R&D money and decades of experience, I don't see Mistral pulling it off. The laws of physics are absolute, no matter how much you spend. I am, however, willing to give up a little fuel economy for a "turbine-like" engine that is happy to burn cheap Mogas. That's why Mistral is on the short list.

Whatever I buy, I like the idea of a single-lever FADEC system or equivalent. This is where inexperience comes into play. Fooling with all those pinball game plungers on the panel doesn't turn me on. I'm a child of the video game era. I'm a lot more comfortable around electronicized engines than I am with carbs and magnetos. I understand WHY traditional Lycs and Continentals are the way they are, and I have no argument with people who like them. No need to convince me. But that's just not the way I roll, I guess. I like the "looking out the window" aspect of flying, not the fiddling and fussing aspect. As long as there is complete redundency, I'd much rather have computers running the show. They're far better at it than I could ever be. I want to set it, forget it and eat some Fritos.

If you are new to aviation, buy a simple, proven powerplant. You really don't need to dabble in experimention while learning to fly (IMHO). Like crosswind landings and slowflight, mixture management and carb heat usage is part of learning to fly. 50 years from now they might be gone, but manual engine operation will be with us for some time to come.

Speaking of the video game era, how many motherboards, harddrives and video cards have you smoked in the last 10 years? I've had several of each.
Dual mags and constant flow fuel injection still look pretty good to me.

John

 

[cobra]

George,

Tracy Crook is a world class cheapscate- he strives for efficiecy and use of cheap, easy-to-find parts. He ran in the 160 class with his early non-injected intake- he used 3 old side-draft motorcycle carbs at the time. Things have improved since the early trials.

The stock 13B's were rated around 140HP by Mazda; the newer Renesis is rated closer to 200; the 3-rotor engines around 250 without turbocharging. Porting (timing) improvements and manifold design make up the differences reported by everyone. 180HP is easy with fuel injection and porting, 250-300 with turbocharging.

With all of the percieved shortcommings you refer to, Rotaries have no problem putting out gobs of power- the reason Wankels are not allowed in any of the sanctioned races these days. The design of the intake manifold is important for economy when these engines are run at a constant 6000+ rpm. Your sports car analogy does not really apply, the car engines are tuned to enhance low end torque, not provide high-rpm continuous operation.

The Powersport Rotaries you (Vans) refer to used old school fuel system- the more modern systems use fuel injection with adjustable fuel levels that allow the mixture to lean out far below the motors with aluminum pistons. I wouldn't necessarily call the tests bad, because they did put several planes thru the ropes, but the tests were somewhat biased against the current crop of rotary performance and hardly represent state-of-the-art. Time will tell on that front, I think you might be impressed.

Because rotaries love fuel injection and forced induction (turbo charging), they have no problems at all in the 300 HP arena, as long as the cooling system is designed accordingly.

It is true that a few racing rotarys have blown up and swallowed parts, but be fair, those engines typically are pushing 30 psi+ boost and running over 10,000 rpm. I wonder how your Lyc would do under the same conditions??? Truth is, the rotaries are far more durable in normal and even in race conditions, where similiar piston engines normally get overhauled after each race. Look at the endurance races Rotaries dominated before being outlawed by pissed losers. FWIW, I must have missed something, I thought Lyc suggests continual operations at (lower than) 75% of rated HP...

As far as the oil thing, current thought is either mix oil with the fuel and eliminate weight from pumps, injectors, or, use clean burning 2-cycle oil in a separate system, to cool the rotors, and use a high-quality synthetic in the crankcase. I personally like the latter option. No one uses the OEM system designed for the public.

Id put the most likely failure path on Lycs (and probably any air cooled engine) around the valves/heads, particularly on the exhaust valves. You suck in an exhaust valve, your engine stops. Next likely problem has involved crankshaft failures. Rotaries have no valves at all, and the crankshafts are bulletproof. A failed rotary (failed seal) will generally continue running until it is intentionally stopped- they lose compression and run at reduced power, but they still get you back home. Id put the most likely failure mode with rotaries in the fuel injection system and possibly with electrical malfunction. Most of the current designs have redundent systems just like the certified motors do.

Bottom line: most performance issues between Rotaries and certified motors are moot- a toss up, some a little more powerful, some a little less weight; all depends on the specific installation. Lycs generally cost more up front and far more to rebuild/overhaul, but they have been around long enough that installation is easy. Any alternative system will involve a bit more work; the rotaries ARE far easier to work with in a home garage environment, far more forgiving.

 

[gmcjetpilot]

I love Wankels

Look I like rotaries. I think they are reliable if the installation is done properly.

I like Tracy because he is a cheapskate. Tracy ditched the side draft set up long ago. The race I am referring to is Sun-N-Fun last year. Regardless I still detect a disconnect between claimed HP and performance of all alternative engines. It's not what Mazda claims, it's what gets to the prop.

As far as my sports car analogy, I accept your comment that it does not apply. I say it gives a clue to realtive economies but not a direct comparison. I think Mazda did all they could to get the sticker MPG as low as possible. They missed it by a 5 mpg compared to a piston equivalent for both CITY and HWY milage. You can discount that; I think it is relevant.

I have heard of excuses and reason why the rotary is not a little hungry-hungry hippo on the fuel. Look just prove it. Get a rotary out to Vans or any where where a RV of the "Lyc kind" to fly off. Do a full day, weekend side by side test: X-C, time to climb, top speed and so on.

The turbo debate - Great, turbo it. A Lyc can be turboed easily. It adds efficency to any engine, but it also adds cost, weight, complexity and maintenance. I say the RV is not an ideal plane for the high flying turbo mission.

Yes Lyc recommends 65% power, 400F CHT or less and oil temp 165-220F. Tracy suggest using Wankel's of mild HP, not hot rod versions for aircraft use. Call Lycoming and ask about the countless hours of test cell runs they have done over the last 1/2 of century. The Lycs have gone over 2,500 hours or more. The Lycs that don't make TBO are from dis-use, followed by mis-use and poor maintenance. I would admit the rotary may be less sensitive to dis-use or mis-use may be, but who knows? I think pointing to the Lyc as somehow not reliable or prone to catastrophic failure is a losing argument not backed up by statistics. If that is a justification for using a Wankel it is a weak one.

Lyc valves - They can stick, burn but they usually don't just fail. I have a friend who's Lyc idled rough when cold, due to a partial sticking valve. This was due to deposit build-up in the guide. He fixed it in a few hours with the engine and cylinder still installed for pennies. (It's called the rope trick, where the valve is dropped into the cylinder to clean the guide. Beauty!) Reason for deposits? Poor maintenance or running too hot. Clearly the Wankel has an edge with no valves, granted. Again its a moot point if you maintain and fly an engine properly.

Lycs cost more to buy and overhaul? I say you get what you pay for. You're buying an aircraft engine which you expect 2000 + hours of trouble free service with routine maintenance (and no tinker time). It's an engine that can be worked on at 1000's of airports by 1000's of mechanics country and world wide. With a huge inventory of standard parts and tools, so there is a Lyc service advantage.

Granted a homegrown Wankel can be bought from a salvage yard and overhauled. To compare a homegrown Wankel you need to compare it to a used Lyc, with a homegrown overhaul. The price difference is small, especially when your time is accounted for. The alternative cost advantage is non-existent, since the Lyc will go together quicker. However for the experimenter this is not a factor. I respect the fun of coming up with something unique, but lower cost is not really a great reason for an alternative engine. Clearly the market is for new engine kits, both Lyc/clone or alternative. The NEW FWF alternative engine kits as we all know are not a bargain (hey they have to eat). The person who buys these is less likely to do a do-it-yourself overhaul down the road.

The ship has sailed on the idea that any alternative engine is going to save you time and/or money for comparable performance. Alternatives are for those who love the challenge and want something differnt, which is cool and awesome. I only campaign that builders be realistic expectations on what the results might be and what they say about Lyc's, like reliability claims not backed with facts.

Tracy Crook is a world class cheapskate

The stock 13B's were rated around 140HP by Mazda; the newer Renesis is rated closer to 200; the 3-rotor engines around 250 without turbocharging.

With all of the percieved shortcommings you refer to, Rotaries have no problem putting out gobs of power.

The Powersport Rotaries you (Vans) refer to used old school fuel system- the more modern systems use fuel injection with adjustable fuel levels.....
(Wankel's are inherently not fuel efficient and due to the combustion shape, regardless of ECU or leaning.)

It is true that a few racing rotaries have blown up and swallowed parts, but be fair, those engines typically are pushing 30 psi+ boost and running over 10,000 rpm.
(Reliability of the Wankel core parts has really ever been in questioned. I would worry more about the reduction drive and ECU, both reliable but subject to failure.)

Id put the most likely failure path on Lycs (and probably any air cooled engine) around the valves/heads, particularly on the exhaust valves.
(May be true, but total valve failure is rare, but point taken, a Wankel has no valves to fail. Most Lycs fail to run because the pilot ran out of fuel. The Wankel is not immune from this avoidable operational mistake.)


Lycs generally cost more up front and far more to rebuild/overhaul, but they have been around long enough that installation is easy. Any alternative system will involve a bit more work; the rotaries ARE far easier to work with in a home garage environment, far more forgiving.
(Your opinion and respect it. I think a Lyc is easier to work on by an amateur builder.)

 

[Jconard]

1st,

The idea of auto conversions has been tried since forever...numerous early airplanes used the Model A Ford engine. It is not that aircraft engines are easier to install because they have been around longer....it is simply that AIRPLANE ENGINES install better in AIRPLANES...see the connection..

2nd,

Rotary internals do fail, and when they do it is spectacular. They do not convert fuel to motion as efficiently because of the design, they waste alot of heat energy out the exhaust, which is also why they respond so well to turbocharging.

3rd,

Rotaries can be used in club racing in a number of classes, including ITS, ITE, and of course Formula Mazda. They were always under a multiplier to ensure parity between displacement, just as were the large 2-cycle 8's that were used in the D Sports Racing class. By the way, in improved touring the mazda was never really competitive with other cars, and that is why there is now a spec rx-7 class. It has been repeatedly tried in C sports racing, and only was competitive in the hands of a particular racing family who mated it to the ultimate conversion chasis (The Ralt RT-5), and were years ahead on body aerodynamics...more downforce, less drag.

In the IMSA series, they never got the ratio correct, and in point of fact what kills the rotary in every top level series is FUEL LIMITS. That's right, in most road racing there is a limit to the fuel a team may use, or in the size of the fuel tank. So, fuel vs power disparities either run you out of gas, or force you to pit more. This is why the rotary is not used any longer at the upper eschelons of racing.

These shortcomings could be overcome initially because Mazda was ahead of the other teams with turbocharging, but when everyone learned how to use it, and when boost levels were limited or turbocharging eliminated, the piston engines killed them.

4, As to valves, have you ever seen them? The exhaust is a MASSIVE 7/16 sodium filled stem, no one can remember a failure. The intake is nearly as large. Parts can be this massive because the design is slow turning.

Remember, inertial load increases at the SQUARE of Speed, but is only linear as to weight.

Remember, that there is no rotary engine yet that has lived at 6,000 rpm for 2,000 hours.

The vast majority of engine failures with lycoming are soft failures, and happen with much notice....

1. cam and lifter...most often from misuse, engine gradually loses power no catastrophic failure.

2. Mag Failure...mags give plenty of advanced notice if you do mag checks and know your plane. They never both fail at the same time.

3. Crank failures: Extremely rare. Extremely rare. Almost every case I am aware of in 4 cylinder GA engines was an unreported prop strike which became a failure later. There are SB's, and there have been some failures, but it is an infinitesimal amount. Maybe Car cranks and PSRUS will hold up better, maybe not. During the time I wrote this, more lycoming four cylinder, direct drive hours were flown in North America, then all the rotary or subaru time in the world.



Finally,

A carbureted lycoming has NO WIRES or Control Cables, which, if they fail, will stop the engine. Can you say the same?

When you learn to fly, and get some hours, you may wonder how much risk to take with power, in a high wing and span loaded aircraft. But please remember that there are some engineering principles which apply:

1. In any given problem, a system with fewer parts is always more reliable than one with more. (I said system...remember)

2. Acceleration forces increase exponentially more fast with speed than they do with weight.

There are more moving parts in 4 injectors, than in one carburetor.

A direct drive engine has no gears in the power path.

A mag has only three moving parts...points, generator rotor, and distributor rotar. These go hundreds of hours with only minimal maintenance.

An o-360 with carbs and mags, and hartzell cost $19K plus $6k prop. Will go an easy 165kts on 8 gph for 2,000 hours. Every airport in America will have someone who knows it, and you will benefit from the vast collective knowledge of General Aviation.

Can you create a system with the above performance, for the above cost? Doubt it.

Oh yes, I will save it all back at rebuild. Of course all the cheap auto rebuild stuff is a dream, but even if it were true, I don't save the $10K under I reach TBO, and only if I reach it trouble free.

Has anyone done that? With a Subaru or Rotary, and similar fuel/speed...

Didn't think so.

Oh, another 1,000 lycoming, four cylinder, direct drive hours have just been flown again....while I was writing....

 

[rv6ejguy]

In the IMSA series, they never got the ratio correct, and in point of fact what kills the rotary in every top level series is FUEL LIMITS.

These shortcomings could be overcome initially because Mazda was ahead of the other teams with turbocharging, but when everyone learned how to use it, and when boost levels were limited or turbocharging eliminated, the piston engines killed them.

The vast majority of engine failures with lycoming are soft failures, and happen with much notice....

3. Crank failures: Extremely rare. Extremely rare. Almost every case I am aware of in 4 cylinder GA engines was an unreported prop strike which became a failure later. There are SB's, and there have been some failures, but it is an infinitesimal amount.

Mazda never raced turbocharged Wankels in IMSA. They raced atmo 13B 2 rotors in GTU very successfully, 3 rotor 20Bs in GTO, not quite so successfully but won the drivers championship if I remember correctly, then the 4 rotor 26Bs in the beautiful RX-792P and Lemans winning 787. They won over 100 major victories in IMSA including many 12 and 24 hour races. They have proven to be one of the most reliable engines ever raced. To say that a professionally assembled 200hp Mazda rotary core running at a paltry 4500-6000 rpm is unreliable is simply absurd with no basis in fact.

Renault, Porsche, Ford and Nissan ran turbos early on followed by Toyota, Jag and Audi somewhat later.

While we have no way to trace Lyco crank failures and exact causes, these happen more often than some people think. Just one for instance: Lycoming TIO-540 and LTIO-540 engines made between March 1 and Dec. 31, 1999 suffered 14 crank failures apparently caused by a metallurgical defect. This prompted an AD and a lawsuit (there were fatalities).

We really don't know how many 4 cylinder Lyco cranks break due to the recent "problems". I agree than many cert engine failures are "soft" but I know of a handful, first hand within the last 3 years which were not. My first hand knowledge is a drop in the bucket compared to all the Lycos flying so there are probably quite a few failures that many of us don't see or hear about.

Who really cares. People will fit want they want to and we all have different reasons for those choices. For most RV builders, a Lyclone is probably the best choice to get into the air reliably and quickly with the least hassle. Cobra, Bill and I just won't have one of these out front and many others are fitting non Lyco power these days. The trend is stronger than ever after all the crank recalls lately.

 

[Jconard]

While we have no way to trace Lyco crank failures and exact causes, these happen more often than some people think. Just one for instance: Lycoming TIO-540 and LTIO-540 engines made between March 1 and Dec. 31, 1999 suffered 14 crank failures apparently caused by a metallurgical defect. This prompted an AD and a lawsuit (there were fatalities).

We really don't know how many 4 cylinder Lyco cranks break due to the recent "problems". I agree than many cert engine failures are "soft" but I know of a handful, first hand within the last 3 years which were not. My first hand knowledge is a drop in the bucket compared to all the Lycos flying so there are probably quite a few failures that many of us don't see or hear about.

14 out of......

In fact we do know, the accident reports, and the experience of numerous engine builders, including my local machinist (thousand and thousands over 40 years) trace crank failures to unresolved prop strikes. They can tell because there is a point where the crank shows evidence of a strong hit...then propagation...then failure.

EJGUY: I appreciate your approach, and I know many in the aircoolde VW scene (my other hobby) who like your fuel injection. You seem perfectly willing to say that you prefer the chance to experiment...fine. But many people buy into the hype. I can agree with the statement that one may install a conversion, be willing to weigh more, and fly slower with more fuel, and more complexity. The further comments below are not directed at EJGUY:


But, the constant rhetoric about reliability, power, etc...is not born out by the facts.

It is the kind of thing where everyone knows that a new purple PSRU is cool, innovative and durable...heck any ONE of those belts could cary the whole load. They get sold to customers at an airshow. Then a piece of something (allegedly) takes out one belt and the unit fails completely. Or it simply failed completely and there was no debris. (hard to believe that any mechanic would hack off a chunk of aluminum and then go flying with it in the cowl..harder still to believe that it would bounce up and forward and into a belt).

An accident that could have easily killed someone, and then the (now labeled prototype) unit is withdrawn from the market. Followed by the sound of the Kool-Aid drinking fans giving Kudos to the experiment.

But should we forget that all the experts on this site just Knew that the design was sound, just Knew that any one belt was sufficent, just Knew that the design showed leadership?

Kind of like a number of people who do not currently fly, have never built an engine of any kind, just Know that all those systems and designs will provide better, more reliable power, for less fuel....

For the sake of the future of homebuilding, I honestly wish that there was more control on FWF implementation.

Back to EJGUY, I watch your site with great interest, you seem to have the background to develop your implementation and test it....but many do not, they will casually assure themselves that it is as simple and reliable as you make it seem. This scares me because when crashes happen it gets attention. The further any design is from "best practice" or industry custom, the closer it is to actionable.

I know this may get some flames.

 

[cobra]

Jconard,

Since you asked, I know of several mazda engines that have run very near 2000 hrs in an aircraft- the most time I know of was in a training gyroplane, where the service cycle is probably greater than in fixed wing service- that engine went over 2400 hrs before overhaul which turned out to be unneeded. I believe Tracy Crook took his 13B to around 1800 hrs before he traded it in on a newer Renesis motor, mostly to test his new redrive/big prop, not that it needed replacing- that engine had NO measurable wear in any of the bearings or apex seal, and that engine was taken out of a junk yard (used RX-7) if memory serves.

The only reason you have not yet seen more reports is simply that the Mazda conversion parts have only become available commercially in the last few years, and it takes a bit of time for the GA pilots I know to log 2000+ hours

FWIW, The complete overhaul kit in a Mazda costs around $600, if it is ever needed. The most common failure (I believe) involves rubber seals that can can become damaged with excessive heat (cooling system failure). To claim wear-conditional parity with a Lycomming is absurd; many Lucs do not make it anywhere near TBO for whatever reason, though granted, some do if babied, maintained, and used regularly. I do know that a Lyc overhaul costs a bit more than a Wankel.

Im glad you are happy with your Lyc- it is an excellent choice for most of our clan. I really only object when I hear false reporting and biased facts thrown out, which gives a twisted impression on an engine that appears to be as good, if not better, based on engineering principles.

I think you can bank on the fact however, that a properly tuned Mazda engine will run a lot longer at rated full power, 6000 rpm, than a Lyc will at 3000. I suspect we will be able to say the same thing about Subarus as well, though I think the Wankel has an inherent advantage over any reciprocating engine operating at continuous "high" rpm. (remember, the rotors turn at 1/3 crankshaft speed in a continuous motion < do not change direction 4 times per power stroke>, and the rotors do not need to be made light/flimsy like alumimum pistons and connecting rods).

 

[rv8ch]

Proceed with caution

I know this may get some flames.

I think your points are very valid, and should be carefully considered by anyone contemplating an alternative engine.

Experimental avation is not for everyone, and neither are alternative engines. I can't speak for the rest of the "cool-aid" drinkers, but I have to say the number of catastrophic failures of lycoming engines is what directed my attention to alternatives.

Just about every pilot has personal knowledge of a lycoming that has suffered a catastrophic failure, or has suffered one themselves. When I compare that to the automotive engine world, it's a different story. The only auto engine I've seen have a catastrophic failure was back in the 70's at Smokin' Alamo Dragway when one of the top fuel funny car drivers blew an engine and I ended up with a *very* hot piston as a souvenir. I don't really think that counts.

I have never been able to find a single source that discusses aviation engine failures and their causes. My reading of a lot of NTSB reports seems to indicate that aviation engine failures that end up there are catastrophic failures. Alternative engine failures that end up there are supporting system failures. As a builder, I don't have any control over the metalurgy of the engine's crankshaft or other critical components. I do have much more control over the supporting systems.

This is my thinking today, and I reserve the right to change my mind at a future point in time!

 

[Jconard]

many Lucs do not make it anywhere near TBO for whatever reason, though granted, some do if babied, maintained, and used regularly. I do know that a Lyc overhaul costs a bit more than a Wankel.

Actually the lycs that regularly exceed TBO are usually the ones most over used...flight schools, as the most common failure is cam wear caused by rust, nearly always results from non use.

I do not know of ANY catastrophic lyc failures. The one crank failure I have witnessed was from a prop strike, it craked all the way through on the front journal to rod fillet, engine ran rough and made reduced power for the 30 minutes it took to reach safety.

Tracy made 1800 hrs..geat, and maybe a gyro plane...so there's two...


I think you can bank on the fact however, that a properly tuned Mazda engine will run a lot longer at rated full power, 6000 rpm, than a Lyc will at 3000. I suspect we will be able to say the same thing about Subarus as well, though I think the Wankel has an inherent advantage over any reciprocating engine operating at continuous "high" rpm. (remember, the rotors turn at 1/3 crankshaft speed in a continuous motion < do not change direction 4 times per power stroke>, and the rotors do not need to be made light/flimsy like alumimum pistons and connecting rods).

Flimsy...have you ever seen the pistons and rods on any engine let alone a lycoming? One of the advantages of low rpm is that parts can be built closer to the heavy end.

You are theorizing what "must" be, but there is no patent on the basic Wankel design, which has been forever...do you think Honda, Lycoming, and Continental are stupid? If you really sat down to design a clean sheet aircraft engine I suspect you too would do what Honda did, design an opposed, low RPM, large bore piston engine.

By the way, the rotor changes direction several times per revolution, placing tremendous stress on the rotor housing and gear drive/eccentric.

You can guess as to what will be, and perhaps theorizing is fun, but you do not KNOW, as there simply is not the depth of operational experience in you or in the engine package.

 

[cobra]

My choice of the Wankel engine is largely based on basic design considerations. Im not saying that piston driven power does not work, even work well in many cases, just that I believe the Wankel is a better design given the characteristics of our aviation environment where safety and reliability are most important.

"One of the advantages of low rpm is that parts can be built closer to the heavy end."

Can be- they need to be... the design is a compromise from the get-go. As long as we are theorizing, I agree with your point so long as the stroke is short (generally with a large diameter bore); trouble is, the Lycs use both heavy parts AND a long stroke to get the power/ displacement needed. Long strokes put significantly more internal stresses on all internal parts (the crankshaft, rods, bearings, and piston pins) as the piston is forcerd to accelerate, decelerate, stop, accelerate, decelerate on each stroke. Add the little demon of preignition, from heat accumulation related to air cooling, the forces act much like a sledge hammer on every internal part.

FWIW, That long stroke is also the source of the famous Lycomming vibrations/power pusles, made worse by the air-cooled loose internal tolerences which also aggravate high wear characteristics. Same is true with the Lycs close design cousins, Harley motorcycle engines and some older tractors.

The big automakers did not chose to go rotary simply because it is not a great engine design for an automobile- limited low end torque limits use to high rpm operation and frequent shifting. I mentioned before that the power/torque curve in a nrotary is linear with rpm, unlike the bell shaped curve common to a reciprocating engine. I believe the rotary is a much better aircraft design than it is for cars, simply because aircraft operate at a consistent (high) rpm w/high torque requirements and it is inherently a high output/low weight design. It is not as great as a turbine (were they sized for our needs and available ), but better than bouncing pistons.

"the rotor changes direction several times per revolution"

No, it does not! There is a small measure of eccentricity in the motion, but the rotor does NOT change direction. High rpm stresses concentrates on the ring gear (in compression, not in shear direction btw), which needs to be upgraded in race engines that operate > 10,000 rpm (a common upgrade, accross the counter availability). The gear's durability is a non-issue at normal engine speeds <7000. The rotor housing normally only sees slight direct pressure from the springs under the apex seals.

 

[rv6ejguy]

While we have no way to trace Lyco crank failures and exact causes, these happen more often than some people think. Just one for instance: Lycoming TIO-540 and LTIO-540 engines made between March 1 and Dec. 31, 1999 suffered 14 crank failures apparently caused by a metallurgical defect. This prompted an AD and a lawsuit (there were fatalities).

14 out of......

But, the constant rhetoric about reliability, power, etc...is not born out by the facts.

It is the kind of thing where everyone knows that a new purple PSRU is cool, innovative and durable...heck any ONE of those belts could cary the whole load.

An accident that could have easily killed someone, and then the (now labeled prototype) unit is withdrawn from the market. Followed by the sound of the Kool-Aid drinking fans giving Kudos to the experiment.

For the sake of the future of homebuilding, I honestly wish that there was more control on FWF implementation.

Back to EJGUY, I watch your site with great interest, you seem to have the background to develop your implementation and test it....but many do not, they will casually assure themselves that it is as simple and reliable as you make it seem. This scares me because when crashes happen it gets attention. The further any design is from "best practice" or industry custom, the closer it is to actionable.

I know this may get some flames.

14 of ...

I believe the number was around 300 engines so a pretty high percentage. This was only part of the story: A class action lawsuit was filed against Lycoming concerning an alleged 10% inflight failure rate on its TIO-540-AE2A engines powering Piper Mirages. This engine has a TBO of 2000 hours however, a survey of 92 owners found that only 4.3 percent made it to 1500 hours. The average was 727 hours. 41% needed a top everhaul before 1000 hours and many needed topping at 200-300 hours. Why Lycoming sets the TBO at an unrealistic 2000 hours is puzzling when probably not one engine ever reached that without topping. If it was set at a more realistic 750 hours, owners would expect a more realistic operating cost.

The core reliability of most auto conversions is well established and would seem to be at least as good as Lycos. I'd be the first to admit that the supporting systems reliability is not and these have caused 95% of the forced landings and crashes. This is the area where we experimenters are trying to improve and come up with solid design recommendations for others to follow.

Power is what you'd expect from engines turning X rpm and looking at factory power curves. Many have inflated these claims and generally when flight tested, these false claims are exposed. My view is that light turbocharging is the way to go to keep rpms below 5000 for takeoff and 4-4500 in cruise while improving power to weight ratio and altitude performance. Experiments on the 13B with turbos is ongoing with people like John Slade now having good success with a Garrett turbo I matched for him.

I caution everyone I talk to that alternate engines are not for most people and there is more than meets the eye. When I give technical talks to our chapter here, I tell people the same thing. There is great interest in the topic.

Jan's belt drive didn't work out just like Lyco's engines above or things like the Space Shuttle. Stuff happens. Jan's goals were to offer a drive with different ratios for different airframes and power requirements and at a lighter weight.
Jan and Tom Moore both accept the risks of test flying development parts, someone has to do it. Jan made the decision that this was not the way to proceed after the forced landing despite the funds and time expended on it. Without new ideas and validation through testing, no improvements will be made in any field. I had my reservations about the drive and how much testing would have to be done to prove it. I still admire Jan for the innovative idea. Like some of my ideas, they just don't work out and we have to move in another direction.

Understand that "we" are trying to establish the "industry standard" or norm for systems on these conversions to make them as reliable and safe as possible. Work is focused on several areas: electrical- redundancy and warning, redrives- reliability, torsional vibration damping and weight reduction, fuel system- reliability and redundancy, cooling- packaging, drag and weight reduction, performance. Frankly few of us worry about the actual core engine reliability as this is well established with billions or trillions of hours of operation in the vehicles and in torture testing by the OEs, efforts and engineering wise which dwarf anything cert aircraft engines builders have ever done.

We simply do this stuff because we love it and it is very interesting. In my case, aviation is becoming a larger part of my business and I feel I should be flying what I sell.

 

[Yukon]

Newbies and Alternatives

Good post RV6ejguy!

I agree with most everything you said. If you are being honest with your customers about the added risk of engine experimentation, and they do it anyway, then your job is done.

Egg is now embarking on his 4th generation gearbox. He is shooting for a 2 to 1 ratio, inspite of his own listers telling him it will be subject to resonance. Of course those same guys told him belt drive is best left on tractors. I applaud his pioneering spirit.

Good luck with your new RV-10.

John

 

[Jconard]

First,

Given proper rod angles, etc, there is nothing wrong with long stoke, the O-320 only has a stroke of 3.7 ish and the H6 3.50, the 360 is a little over 4. Short stroke, large bore is called oversquare, and is a design favored for its High rpm ability. I guess I don't understand your point...first you said the internal parts were flimsy, and now they are too heavy. These parts are pretty well engineered and the manufacturing is really first rate. (The casting mfg for deltahawk for example casts and machines superior's cases)

Could things be lighter, hand finished billet rods, and forged pistons? Sure, but why? At 2700 rpm the stock parts are plenty stout. In the interest of full disclosure, I did trade my stock pistons for forged units, not for compression, but because they came more closely balanced, and the cost was about $500 for all for on exchange.

Second if you think that a spining triangle, within a double elliptical chamber does not change directions....well where are you on the whole "sun rising in the east thing". Any radial inertia vectors you would own up to? If the only side loads are seal springs, why do crank failures case the rotors to blow out the side of the case?

I have built a ton of air cooled engines, and raced for more than a decade, I have seen the best components that money can buy. I was initially attracted to the Egg package when I was thinking about an empenage. It did not take me and my dad (4000+ combat hours M.E. CPE) long to see that vitually every answer, on every website, from every vendor was something like "No failures have ever been seen". Gave me the willies. I could not find any way to do this without a ton of money, and for less performance.

But no one in the movement would ever just say "Hey, you're right, we just think this is neat, and are trying to evolve the approach, but right now it is heavy, and slow, and involves substantial additional risk."

Finally, there is a distinction I have never understood in these discussions:

Frankly few of us worry about the actual core engine reliability

Why not? There are numerous additional failures which are possible which can kill you, which will fail the delivery of power.

The very technology which is "superior" creates these single points of failure. Again, carb, mags, O-3XX there are no cables, and no wires, and no charging system that will ground you.

So this superior technology creates complexity, which creates a need for even more complexity to make it reliable, which makes it all, well.....complex, and heavy.

By the way, the lycoming TSIO failure lawsuit was a bit more complex, it was a multi-party litigation where the subcontracting foundry was unable to meet its indemnity committment, and the marketing party (Piper) was off the hook, no lawsuit of that complexity is that simple. I have read the case. I have not seen it on any of the free law resource sites, but most public libraries have Westlaw access, where it would be available.

All I am saying is that I object to the rhetorical claims of predicted reliability.

Again, I know this will get flames. Maybe in another decade the package will be refined.

 

[rv6ejguy]

All I am saying is that I object to the rhetorical claims of predicted reliability.

Again, I know this will get flames. Maybe in another decade the package will be refined.

Well I don't worry about the core reliability of my Soob because the EJ22 engine has accumulated well over 100,000 flight hours to date by RAF rotorcraft alone to date with ZERO catastrophic failures to my knowledge. However this does not mean that the next time I strap my 6A on that the engine will not fail any more than the next time I strap a Lyco powered aircraft to my butt that it won't fail. Statistical probability will be the last thing to cross your mind if the prop stops.

I prefer to be prepared with current training and procedures for that possibility. I try to mitigate risks by making (hopefully) good decisions before pushing the throttle forward. I don't have blind faith in any single engined aircraft and in many ways take less risks than some of my Lyco friends might who seem to think that flying is like driving a car- just hop in and go.


Of course the whole idea gets a bad name every time something doesn't work out and causes a forced landing or crash. Instead of thinking this is all bad, I like to be able to learn something from these incidents which can be applied to my designs to improve them. I've certainly learned a lot in the last few years from my mistakes and others.

It must be remembered that there is no large company with millions and a battery of savvy engineers doing this development work on alternative engines. It is small companies with limited resources and private individuals using LAR (looks about right) engineering for the most part. Evolutionary, incremental improvements slowly filter in to advance the the safety and performance of auto engines in aircraft. With things done in this way, there should be little wonder that bad things happen on occasion. All the money and talent in the world does not guarantee the success of an engineering project. I'm thinking Shuttle, V-22 here as a of couple examples. Far more complex machines than my -6A to be sure but billions of $ and thousands of the best engineers available and still mistakes are made after years of development.

On the other side of the coin, I object to the reverence that so many people have here for the Lycoming engine with the seeming head buried in the sand notion that they never fail. Yep they do. The crankshaft ADs are real and are turning a lot of people off these engines even if they don't break in use. Some people are having to spilt the case to put a second or third crank in. That's not right after 30+ years of "development" and making many at least look at alternatives. I must say it makes me think about it when I fly in a Grumman or 172 now. Hmmm. Wonder if this one has a good crank in it. Fortunately all have been fine to date for me!

I always like alternatives whether it is in cookies, colors, cars, planes or engines. One flavor can be boring even if it's chocolate. The few here just love to flame the whole concept of alternative engines while I prefer to present some information on new developments and milestones. If you like your Lyco, please, by all means fly it and enjoy it. We'll happily continue flying our heavy, fuel guzzling but smooth running, sweet sounding auto engines.

 

[Yukon]

Thanks!

We'll happily continue flying our heavy, fuel guzzling but smooth running, sweet sounding auto engines.

Thanks RV6EJguy! Now we are getting somewhere!

John

 

[Jconard]

The crankshaft ADs are real

Nice to have warning based on engineering and analysis across the entire GA industry. Like I said before, unexpected failures are extraordinarily rare.

I prefer to be prepared with current training and procedures for that possibility

When I was a young roadracer, some hotshoes claimed they had less need to make good risk decisions, because they had the car control to get out of their mistakes. I learned (from some excellent French Canadians) that it is best to minimize your reliance on skill to get out of situations you may have avoided.

The other approach put many young drivers in the wall at ovalls, and in the hospital in quicker cars.

Oh yeah, the teams that let us drive or rent their 300K cars appreciated a lack of damage.

By the way, you are just plain da*n lucky, I read your report about a year ago. I understand the final landing was a -7G pankake. This is plenty to kill or paralyse a human by compression fracture. You walked away, and it is I am sure an attribute to your skill that it was only -7G and not more, but wouldn't you agree that the situation was best avoided?

Again all I am saying is risk management, probability of unexpected failure. In all of GA the engine stopping acounts for less than 3% of crashes. The vast majority of those are actually fuel starvation. That's across Millions of hours every year for 30 years.

Lycoming Failure points....
Alternator..NOPE,
throttle, mixture or prop cable fails...NOPE, spring goes to full prop, full throttle, or full mixture.
P-Leads Break...Nope either does nothing or only kills one mag....
Mag Fails....NOPE another mag,
Engine fuel pump...Nope electric will work,
Electric pump fails or no power...NOPE mechanical pump keeps running.

Connections: One hose, two wires and three cables.. $25,000
Performance: Easy 165KTS at 8 gph: $25,000 (same)
Saving 100 LBS No extra Money


Avoiding corn field landings.....PRICELESS

Kinda nice really.

We'll happily continue flying our heavy, fuel guzzling but smooth running, sweet sounding auto engines.

So long as we all agree.

 

[rv6ejguy]

By the way, you are just plain da*n lucky, I read your report about a year ago. I understand the final landing was a -7G pankake. This is plenty to kill or paralyse a human by compression fracture. You walked away, and it is I am sure an attribute to your skill that it was only -7G and not more, but wouldn't you agree that the situation was best avoided?

I agree that it would have been great to avoid the forced landing and it could have been had I:

1. Had Lycoming power
2. Looked at the ammeter more than once every 10 minutes
3. Had a backup battery
4. Had an aural low voltage warning system
5. Not gone flying that day.

Well, I've addressed points 3 and 4 now plus have a genuine ND alternator now, not a clone.

Lucky, no. I just didn't stall it like others have as this is usually fatal. I flared too late due to the lack of residual thrust having never actually flown with zero power before. Elevator authority is slower and weaker. The field was too rough for the nose gear to take it even with a nice holdoff. I didn't do everything right but I hope to if it ever happens again.

Sometimes we learn things the hard way! By the way, Van's builds a strong airframe. The panel mounted G meter saw -7 Gs, we saw a lot less with 5 inches of temperfoam under our butts- not fun however.

Nothing like a real emergency once in a while to snap us out of our complacency! Learn from my mistakes.

 

[skelrad]

Lucky, no. I just didn't stall it like others have as this is usually fatal. I flared too late due to the lack of residual thrust having never actually flown with zero power before.

In a situation like this, would an AOA indicator have made a difference for you? Or is there too much going on anyway, and having another instrument to look at would just muddy the waters? Just curious.

 

[Rotary10-RV]

Bill, I hope you meant to say "carbon monoxide" emmissions? If it were realy NOS, you'd be plumbing it back into the intake and making even more power.... NOS is a really good oxidizer that burns really fast and they use in racing engines..... Or of course, at your dentist office


Couldn't resist, but I suspect that should have been Carbon Monoxide.... But then again, we all want to know what you were *breathing* and we'll take some!

Alan,
Boy I go away for a few days and the thread runs so far afield I hardly recognize it! Alan, you are of course correct I didn't mean NOS. (Nitrous Oxide) This was a brain abnomaly caused by a early morning start time on my job. What I DID mean was Oxides of Nitrogen which are not the same thing at all. Lean running in Wankel or piston engines can cause them. They are not addressed by cat converters as hydrocarbons can be so auto controllers avoid lean-of-peak.
The He-said-she-said nature of much of the thread following my comments gets really tiring. Lyc's rule, Lycs suck, Wankels suck, Subies rule/suck, Franklins don't suck anymore...etc. What I have been trying to pass along in the alternate engines thread is USEFUL information and where to find it. I started this thread about the MISTRAL ENGINES effort to certify the rotary. The article in Sport Aviation with the so-called test of Lyc's to Rotaries did Rotaries a diservice. Both the engine management system and the exhaust used on the Powersport FWF package were not even close to optimised. Some people really HOPE rotaries use 25% more fuel and this is pure bunk. Mistral has published the weight, (honestly) of their system flying in a Piper Arrow. They have published the fuel consumption figures of their 190 HP normally aspirated engine running on the dyno. The figures are GOOD. Just as good as a carb Lyc's published figures from Lycomings web page and several POH's. Lycomings can probably do better running lean-of peak, no arguement. Lycoming will however void your warranty if your admit to doing it. Fadec won't do better since they do not run L-O-P in the fadec. An aftermarket injection running in an EXPERIMENTAL, or carborator, would be required. Mistral is as I have said many times, is certifing their engines so they will draw crankcase oil to lube the seals, (simplest for the customer) and the amount required is VERY SMALL. They are running ceramic tip seals which require even less than stock auto amounts. The amounts are running as little as the equivilent of 150:1 or leaner oil to fuel mix. That is about 0.9 ounces per gallon. There are some standard aviation engines that burn less than that, and many that burn more. (even 100:1 is 1.3 OZ/GAL) Fact is the Subaru engines probably use the least oil. (burned oil) of any engine as that is a priority in the car. I hope we can look at the available pool of engines as being beneficial to all of US. US is PILOTS. We are an incredibly small percentage of the population and whatever our OPINION of a particular package is we need to make ALL the engines as safe as we can, improve the aircraft were we can and if experimenting, as I will be, try to be responsible enough to design a safe system. If there are any doubts do something conventional so a not to cast a bad light on those of us doing something different safely.
Bill Jepson

 

[N713R]

Way to go Bill

Here Here! (or would that be Hear Hear?)

Well put Bill. Some on this thread are fighting alt engines with fierocity. Some are fighting Lycs the same way. I really can't understand this. If a fellow likes or prefers Lycs, the put one on your airplane. If a fellow like alts, then, you guessed it, put one on your airplane. We are not in Jr. High School anymore folks! Do what you like, and let others do the same. Doesn't really affect you anyway. This should be a forum for idea exchange, and to assist others with the best practices or experiences for their alt engine installation. Not a forum to decide if they are a good idea or not. If you do not prefer alternate engines, or are not interested in furthering their developement in anyway, then please find another forum topic, or shut up.

 

[mlw450802]

... I understand the final landing was a -7G pankake. This is plenty to kill or paralyse a human by compression fracture....

Perhaps not.

excerpt from a nasa report on g tolerance:
"
On December 10, 1954, Lieutenant Colonel John P. Stapp of the Aeromedical Field Laboratory gave an amazing demonstration of a man's ability to withstand immediate impact forces. Stapp rode a rocket-driven impact sled on the 3,550-foot Holloman research track to a velocity of 937 feet per second and received an impact force of 35 to 40 g for a fraction of a second as the sled slammed to a halt in a water trough.26 In February 1957 a chimpanzee rocketed down the track, now 5,000 feet long, braked to a stop, and survived a load of some 247 g for a millisecond, with a rate of onset of 16,000 g per second. And 15 months later, on the 120-foot "daisy track" at Holloman, Captain Eli L. Beeding, seated upright and facing backward, experienced the highest deceleration peak yet recorded on a human being - 83 g for .04 of a second, with 3,826 g per second as the calculated rate of onset. Afterward Beeding, recovering from shock and various minor injuries, judged that 83 g represented about the limit of human tolerance for deceleration.27"

-mike

 

[rv6ejguy]

Here Here! (or would that be Hear Hear?)

Well put Bill. Some on this thread are fighting alt engines with fierocity. Some are fighting Lycs the same way. I really can't understand this. If a fellow likes or prefers Lycs, the put one on your airplane. If a fellow like alts, then, you guessed it, put one on your airplane. We are not in Jr. High School anymore folks! Do what you like, and let others do the same. Doesn't really affect you anyway. This should be a forum for idea exchange, and to assist others with the best practices or experiences for their alt engine installation. Not a forum to decide if they are a good idea or not. If you do not prefer alternate engines, or are not interested in furthering their developement in anyway, then please find another forum topic, or shut up.

Yeah, what Ben said.

 

[Yukon]

Say What????

Ben,

Most people come to this website to make important decisions about how to equip their Rv. What better place to discuss Lycoming AD's, Superior sumps or
the voracious fuel appetite of the rotary engine? Are you saying that we shouldn't discuss the pros and cons of various aircraft engines, only how to install them???

John

 

[rv6ejguy]

AOA

In a situation like this, would an AOA indicator have made a difference for you? Or is there too much going on anyway, and having another instrument to look at would just muddy the waters? Just curious.

The ASI worked just fine. The problem was my brain was having trouble pushing the stick FORWARD to maintain speed as the ground rushed up at an alarming rate. It isn't apparant until you are down to about 75 feet above the deck. This is about the altitude that several RV pilots have stalled it or hit very heavily and been injured or killed as the natural reaction is to pull back to arrest the decent rate. My advice is to maintain 80-85 knots down to about 15-20 feet before initiating the flare. And yes, you are pretty busy with a few things going through your mind!

By the way, forward impacts of 50+ G are routinely survivable in race car crashes, I survived a 35G one myself with only a sore sternum, however vertical impacts are less predictable and anything over 10-15 will likely cause some spinal injury. Land gently!

Sorry for the thread drift here, but this may stick in someones mind in this situation.

 

[PJSeipel]

Ben,

Most people come to this website to make important decisions about how to equip their Rv. What better place to discuss Lycoming AD's, Superior sumps or
the voracious fuel appetite of the rotary engine? Are you saying that we shouldn't discuss the pros and cons of various aircraft engines, only how to install them???

John

Discussing pros and cons are great, but the whole 'insert engine type here' engines suck you should only put a 'insert different type of engine here' in an airplane arguments do get tiresome after a while.

I'd rather hear about what people have done, in an airplane, and how it worked for them than hear the alt crowd bash lycomings while the lycoming crowd bashes the alts.

PJ

 

[Jconard]

By the way, forward impacts of 50+ G are routinely survivable in race car crashes, I survived a 35G one myself with only a sore sternum, however vertical impacts are less predictable and anything over 10-15 will likely cause some spinal injury. Land gently!

Totally agree here, and I have stuffed a formula continental in the wall, closer to low 30's -G.

But, race cars have much better restraints, with the proper geometry between shoulders, hips, and attach points. In addition, you are wearing a helmet, so when your neck stretches (and it willl alot...there are pictures of PT's neck streching over 12" in one crash) and your head hits the wheel, you can survive. If you want to know what happens when improper installation meets open faced helmet.....Dale Ernhardt Sr.

I actually thought about installing a shoulder harness guided on the seat back bulkhead, and/or a Y-tether, like is used in the Citabria/Decathlon to improve the geometry of the RV harness installation...along with a 3" harness. The geometry in our installation is not really correct. There are correct angles that you look for between should and hip, and attach points. EJGUY will know what I am talking about, but earch harness mfg actually ships these diagrams with the belts, and there are several books which include the same guidance....No I did not think about going so far as to "pour" a seat out of the impact beads/resin.

On December 10, 1954, Lieutenant Colonel John P. Stapp of the Aeromedical Field Laboratory gave an amazing demonstration of a man's ability to withstand immediate impact forces. Stapp rode a rocket-driven impact sled on the 3,550-foot Holloman research track to a velocity of 937 feet per second and received an impact force of 35 to 40 g for a fraction of a second as the sled slammed to a halt in a water trough.26 In February 1957 a chimpanzee rocketed down the track, now 5,000 feet long, braked to a stop, and survived a load of some 247 g for a millisecond, with a rate of onset of 16,000 g per second. And 15 months later, on the 120-foot "daisy track" at Holloman, Captain Eli L. Beeding, seated upright and facing backward, experienced the highest deceleration peak yet recorded on a human being - 83 g for .04 of a second, with 3,826 g per second as the calculated rate of onset. Afterward Beeding, recovering from shock and various minor injuries, judged that 83 g represented about the limit of human tolerance for deceleration.27"

Right, but read that those are forward decelerations, where your chest would press against the belts. I was idscussing a vertical impact, where the deceleration occurs in an axis along the spine. The force follows the spine and compresses it. It really takes little in crash scenario to kill you that way because the load is not spread the way it is when you are moved into the belts. The guys that were killed in Lemans ...Mercedes LMP type car...got air, and then when the aero disturbance was over, the car slamned back to the track, all four wheels down. It compression fractured their spines, and that was a flat landing from an altitude of maybe 25 ft, I believe it was estimated in the 8-10 G range.

But, any -G crash along your spine...like a pankake, can kill you, as proven by my former aerobatic instructor, and several drivers at Lemans a few years ago. The instructor died at about -8 in a pankake landing, and I do not think the lemans cars were much above that. Of course the crushable seat pan/rib structure below our "seat" should absorb energy well. My guess is that it is the sudden load that causes injury at these lower readings, and perhaps pilots who are in poor shape compared to active drivers. Before I get flames on the fitness, I will readily admit that I am in horrible shape as compared to when I was racing, and also point out that in roadracing, physical condition is key!

Oh, and the reason I care about which engines get installed, is that to the outside world, the experimental movement will be judged together, regulated together, and face liability together.

 

[cjensen]

Ben,

Most people come to this website to make important decisions about how to equip their Rv. What better place to discuss Lycoming AD's, Superior sumps or
the voracious fuel appetite of the rotary engine? Are you saying that we shouldn't discuss the pros and cons of various aircraft engines, only how to install them???

John

What Ben said is exactly right. If you think about what forum you are currently posting in, this should be THE forum to exchange ideas on alternative engines.

...there is a forum titled "Traditional vs. Alternative Powerplants"...here where arguments are valid and welcome...

 

[RVbySDI]

The ASI worked just fine. The problem was my brain was having trouble pushing the stick FORWARD to maintain speed as the ground rushed up at an alarming rate. It isn't apparant until you are down to about 75 feet above the deck. This is about the altitude that several RV pilots have stalled it or hit very heavily and been injured or killed as the natural reaction is to pull back to arrest the decent rate. My advice is to maintain 80-85 knots down to about 15-20 feet before initiating the flare. And yes, you are pretty busy with a few things going through your mind!

My respect goes out to you for surviving such a landing. I have also experienced an engine out off-field landing that ended in a hard impact due to a "pancake" touch down (well, technically, my nose gear touched down first and folded under the belly of the plane but otherwise was pretty much a hard slam down onto terra firma).

Anyone who has not had this kind of eye opening experience should definetly not be throwing stones at anyone who has. I am continually amazed at the pompousness of our pilot brethren when evaluating the actions of other pilots. We all "know" we would have done things differently had we been in that situation. The truth is, this is definetly one of those experiences that allows for the "you don't know what you are talking about if you haven't been there" statements. It is so easy to look at someone else's reactions and say: "you shoulda done this. . . you shoulda done that."

My experience was not in an RV, but regardless of what type of aircraft you are flying, everyone has the same aerodynamic issues to wrestle with. I had aproximately 30 seconds to make about a dozen very important decisions before I made contact with the hard stuff below me. Your mind is truly racing way faster than you have the conscious ability to keep up with. Everything is in slow motion and in fast forward all at the same time. Somehow you have to make the correct analysis and take appropriate action immediately with every one of those decisions having direct impact upon the next one. There is no time for second guessing nor for second chances.

I, for one, admire you and anyone else who has gone through this as I know first hand what it is like to sit in that seat.

 

[Yukon]

Rotary SFC

Chad,

I disagree. This thread started with someone making the unsupportable claim that Mistral rotaries have an sfc equal to Lycoming. I see no need to post my disagreement in the Traditional vs Alternative section, because in this case, I am not supporting Lycoming, just pointing out that it is highly unlikely that a rotary has the same sfc as a reciprocating engine. (see Van's flyoff).

John

 

[Yukon]

Discussing pros and cons are great, but the whole 'insert engine type here' engines suck you should only put a 'insert different type of engine here' in an airplane arguments do get tiresome after a while.

I'd rather hear about what people have done, in an airplane, and how it worked for them than hear the alt crowd bash lycomings while the lycoming crowd bashes the alts.

PJ

PJ,

Can I suggest you visit the builder's websites for installation instructions? They generally have all that objectionable discussion about fuel consumption, weight and reliability edited out, so that a builder can rest comfortably with his engine decision.

John