David Staten

Secondary, it is possible to build a

Brushless permanent magnet motor

pump combination with no seals.

JCP

Use a magnetic coupling. Magnet is outside the fluid path and is motor driven. Pump impeller is ferrous core, and is inside the fluid path and not directly mechanically linked to the pump drive/magnet.

I would use the manufacturer's recommendation and install it inside the cabin.

 

In a crash, planes tumble.. cartwheel... bulkheads crack. Wings shear, floors buckle. I would rather not add having to worry if the copper tape antenna survived on whatever surface it was bonded to.

 

If you had to roll your own, I'd make a metal whip, 1/2 wave or full wave...

Something that doesn't require a ground plane, and have the whip inside the cabin somewhere.. behind the seats.. something.

Pro:

A steerable nose wheel results in a shorter take-off roll because no energy is lost due to steering with the brakes.

 

Everyone has an opinion on this matter.. and mine is.. that in over 50 hours of flying Grumman Tigers and Cheetahs, after my initial checkout I didn't loose any takeoff performance for this reason (differential braking for steering).

 

I lined up facing a few degrees right of center.. and the initial left turning tendency would center the plane up (on initial acceleration right) about the time the rudder became effective from the slipstream.

 

And with the exception of an RV type, I have to admit that the Grumman also had great short field takeoff performance.. part flaps and climb out right at VX (stall horn blares, but the plane levitates....)

 

Nosewheel steering is a nonissue, when proper training and experience is provided. Its cheaper, less complex, and permits more nimble movement on the ramp.

 

We now return you to your normally scheduled canard issues

I gotta dumb question:

 

What about just making a glide slope (foil) antenna nested on the bottom of the canard. They are quite small. Any splitter is going to decrease the signal to your receiver which means less range.

 

The cost of the foil antenna is restricted to the BNC fitting and foil. You could probably get the foil from someone who has put these type of antennas in already.

Not a dumb question at all.. we've got the glide slope antennae on the floor of the velocity.. one nav antenna in the wing.. the other on the back of the floor of the fuse... all foil.

 

no diplexer needed. no splitting of signal and signal loss.. Just foil.. glass, toroids, coax and tape.

 

And this is on a dual ILS setup (and marker beacon antenna on the keel too, just for grins)

I really feel like a complete noob asking this, but I poked around quite a bit and never saw this specific question anywhere.

 

I'm aware of the CG issues inherent in the Long-EZ design, but is it possible to make a (theoretically) safe modification to allow for a steerable fixed nose gear? Honestly, if I wanted retracts, I'd go full retract. I love the Long-EZ's design, but the hybrid approach to the landing gear really bothers me.

 

Given a long nose design and 50 pounds of ballast (for sake of argument) can a fixed nose gear be realistically done?

 

An alternate idea that I was kicking arouind -- a steerable nose gear system, but with a pinned lower shaft that can be removed -- the nose is kept dropped, but when you fly it, you lift it, install the nose gear (and retaining pin -- Clevis, maybe?) and off you go.

 

I guess if you REALLY know what you REALLY want, I'm sure there's a way to do this. BUT.. you can turn MUCH tighter with a pivoting nosewheel as opposed to a steerable kind. This comes in handy in a crowded group hangar or crowded ramp. Differential braking is the way to go. You dont have to ride the brakes.. Quick jabs to start and stop turns work just fine.

 

Landing with the nose gear up is not a life altering experience. A little fiberglass work and you are back in business, and if you have a TRUE emergency where you need to stop on the ground QUICK, sucking up the nose gear is one way to do it.

 

What bothers you the most? A retracting nose gear or a pivoting nosewheel?

 

Do you feel its unsafe? or you have no experience with this arrangement? Go fly a grumman cheetah or tiger if one is nearby you. Same arrangement (pivoting nosegear) but on fixed gear.

reposted hot off the presses from the Canard Aviator's yahoo group.. from Mr Strong himself..

 

I just replaced a Strong Pitch Trim that stopped working.

On disassembly I found the motor was frozen from rust.It appears that water

had gotten into the motor cavity through a gap between the motor cover and

the welded angle.

This is the first reported case.

To prevent this from happening apply silicon adhesive to that gap Check out

the photo of the fix by going to my PWM website and scroll to the bottom of

the page.

Alex

http://strongpitchtrim.com

 

Dear fellow Canardians!

 

... I have decided on a Velocity SE-RG or XL-RG.

 

Excellent choice... Sorry I am late replying to this thread

 

What I want to do is use two Centurion 1.7, 135 hp jet fuel engines in pusher format.

 

As someone else mentioned, even though this engine makes only 135 hp (on the dynomometer, I presume), you need to understand that this powerplant is being used to replace gasoline powerplants that make over 200 hp. The key is Torque from the Diesels being able to generate equivalent THRUST despite lower HP. What this means: One engine should suffice. Diesel reliability being what it is.. should provide adequate reliability.

 

Becuase cost is a factor, can I buy plans instead of a kit for the XL-RG?

 

As others have said, Velocity is a kit-built plane. In short, NO. The factory manufactures certain parts - fuselage shell, spar's, strakes, doors. If cost is such an overwhelming factor that you cannot afford to buy the kit, then how do you propose to buy ONE Aero-Diesel engine, let alone two? Have you actually checked the prices on them? If you must have a plans built, then I would say go with a Cozy, and if you must, scale it up a few points. The Velocity XL was made to handle the larger engines that people wanted to keep putting on the Standard versions.. its not all that much bigger.. and all that extra HP does is burn more fuel.

 

Now as I said, I am a novice if there ever was one, but I do have a dream. I would like to ask the experienced people on this forum to bring to bear their considerable experince and tell me if it is at all feasible (I don't want to spend the next 10 years experimenting with this either). Any posting about this would be very much appreciated.

If you dont want to spend 10 years on it, then don't deviate from plans doing all sorts of fancy customization ESPECIALLY without a solid background in aircraft design/engineering. I'm not saying DONT do it.. but if you do, prepare to be challenged, and prepare to fix ONE problem and have two or three others pop up as a result of that fix. Deviations from other peoples proven design add time and problems.

 

Flying multi-engine aircraft adds a level of complexity above that of single engine aircraft, ESPECIALLY in emergency procedures (such as one engine out). This complexity demands proficiency, or it will come back to bite you in the worst way. Twin engine aircraft have greater fuel costs and maintenance costs as compared to single engine aircraft. Some people have characterized the cost as THREE times the cost of a single engine aircraft with equivalent seats, due to maintenance and systems complexity. That may not translate as well to homebuilts, but its a good data point to consider.

 

If you have a reliable enough powerplant, what is it about your mission that dictates the need for a twin engine aircraft?

.....you end up pushing the range of the Mark IV over 3000nm.

 

I figure with two pilots (both IFR, oxygen, and piddle pack qualified) we could endure the flight, and actually do private trans-atlantic kinda stuff.

 

Any thoughts?, gotchas? ect?

 

Thanks,

Kyle

You can do transatlantic flight with the longest overwater leg only being 4-500 miles max. I cant for the life of me envision wanting to be in a small plane cockpit for 12-15 hours... but what you describe is do-able.

 

Talk to your doctor about DVT prophylaxis before taking any super long trips like that.

 

Dave

Dave

(CONDESCENSION SNIPPED)

. VERY SIMPPPPPPLLLLLLEEE...

(CONDESCENSION SNIPPED). Yes 3 moving parts thats how I describe it to someone who knows nothing about a rotary engine, that gets the wheels turning.

 

Im all for informed discussion and informed decisionmaking, and while I've come across some very informative persons with regards to the rotary, I also seen more than a few who seize on the notion that 3 moving parts AUTOMATICALLY confers improved reliability and efficiency.

 

I'm not accusing you of this directly, and I'm in no position to seek an apology from anyone. This is more of an open issue. Right now, the jury is out on the reliability aspect, and much of that is the result of the peripherals added, not the core engine itself, but an engine failure and power loss leading to an off field landing or WORSE is a bad event, regardless of wether the core engine or an accessory was at fault. I am speculating that Chris and I will have our rotary fired up and ready for taxi testing within the next 60 days. We are doing a few unique things, on a block that we rebuilt and modified ourselves.

 

I will not kid you that money was a BIG motivator on our powerplant choice and we did our homework. I have read every scrap I can about the rotary, others installs, others experiences good AND bad, and about auto conversions in general. In this vein, I consider myself an advocate for rotary power, but I am cautiously optimistic about how well it will work.

 

Then, they start looking into it themselves then the industry thrives. I'm not going to apologize for anything. You guys want to pick my posts apart have at it. I have an airplane to build and not alot of time to play semantics.

I called BS on the notion that a torque wrench and a $15 set of sockets is all you needed for a rebuild. Thats not semantics. Thats potentially misleading. My OPINION is simply that while advocating in favor of the rotary, you were a little enthusiastic and stretched it a bit. I don't think you intended to lie or intentionally mislead anyone.

 

The same sort of embellishment is happening with fuel burns, power generated, installed weight and so forth in other settings. There's really not that much DATA out there in an aviation setting, so what little bits we have are precious. If someone who doesn't KNOW any better starts basing decisions on little embellished snippets such as these and doesn't get the straight scoop, they are going to feel lied to regarding the rotary... hardly something that will increase our ranks. Its about knowing the risks and weak points and working with them, not putting your head in the sand.

 

Mark isn't a rotary basher either. He's simply a cautious engineering type. I dont always agree with him, and some folks have trouble with the way he says things, but I must admit I find his postings to be rational, accurate when dealing with facts, and defensible when dealing with opinions.

 

I apologize if this has turned into something personal.. that was not my intent. My intent was to set the record straight, firmly, regarding what I felt was misleading information.

 

Dave

In the end, I rebuild my motor with a 15$ set of sockets and a torque wrench. Try doing that with a piston engine.

I'm sorry... I like the rotary.. I rebuilt one, have a second one for a spare, and have torn a total of 4 apart, and I can assure you the above statement is pure BS.

 

The big 2 1/4 inch nut on the back ALONE requires 300 foot pounds of torque. The wrench that can do that is a THOUSAND dollars unless you can borrow one as I did. The NUT requires a socket that cost me $50 bucks new and wasnt available for much cheaper used. Torque multipliers that allow ordinary torque wrenches to reach that torque range rarely sell for under $100 on ebay and cost many times that value new. I needed a heavy duty impact wrench to get that big nut off in the first place, not my ordinary cheap harbor frieght one. That big wrench cost nearly $70 at a pawn shop. I tried a big LONG cheater pipe.. all I did was move the engine around.. the bolt held.

 

I have a full set of metric impact sockets. I have a set of micrometers for measuring wear. I have gap gauges, thread gauges, feelers, a dial indicator.. and I had NONE of this when I started this project.

 

I can assure you it costs a HELL of a lot more than a cheap $15 metric socket set from harbor freight if you want to do the job right and without breaking tools or yourself.

 

I'm very pro-rotary. Im installing one. But I am just as annoyed as Mark when folks "wave their hands and proclaim to the masses 'three moving parts'" That is a gross oversimplification and naive. It does the rotary community a disservice when that gets emphasized above all else.

 

Dave

I'm a newbie regarding these magnificient cozy airplanes, even though I've been lurking for a couple months, learning from you guy's generous & informative messaging. First Issue: I'm seriously considering buying a Cozy Classic project mostly finished which is already equipped with a 1985 Mazda Rotary. Nat Puffer was quoted as believing the Rotary would depreciate the value of the plane. Is this your collective experience, or just his private (now public) opinion?

Thanks...........there'll be many more questions, I already know Dolan

Value is in the eyes of the beholder. Nat is right.. and wrong too.

 

Resale value is practically meaningless if you never plan to sell the plane. The word on the street is that auto-conversions of any flavor tend to have less resale value than certified engines because of the "unknown" factor. This "unknown" factor is a bigger player in true custom engine installs (such as the rotary, since there are few firewall forward options out there, if any, anymore) as compared to packaged auto conversions.

 

To me, if it works as it should, the rotary will perform just as well or BETTER than the certified engine it replaces, for much less initial and continuing maintenance cost. Considering a new engine IO-360 with composite adjustable prop would run over $30,000 new, and I am able to get same if not better performance with less than $7,000 outlay, I wouldnt be offended if the resale value was $15-20,000 less than someone who had an identical plane with a certified package.

 

Im sure if someone had a factory Mistral package installed at its $30,000 outlay it would likely keep its value in a resale scenario.

 

But.. again..those of us building our own dont plan on parting with it anytime soon, and those who have, I have noticed, sometimes offer the airframe for sale separate from the rotary engine, selling the airframe to whomever wants it, and the rotary to others in the rotary community. Best of both worlds.

 

Dave

I'm ordering my plans for the cozy mk iv next payday :-) I plan on using a mazda rotary to power my bird, for many different reasons. I know cooling can be a problem in some installations, and I live in Texas. Has anyone come up with a good cooling system for this specific engine and plane? I think i remember seeing a guy who installed radiators in the wings or strake area. Has anyone tried this? To combat the noise I plan on using a turbo with minimal boost 4-6 psi. What I was thinking is a norimalization trubo like the eggenfeller subaru. Anyone know if this is difficult to do? I know it will me many moons before i need to worry about an engine install but I want to plan it out in the begining.

 

Thanks,

Tim

You need to make an effort to get to the Mid-Winter Rotary fest being hosted by Bill Eslick in GRANBURY TEXAS, right down the road from you. Feb 10-12.

 

http://www.weslick.com/rotorfest.htm

 

You will get to see many many rotaries in person, up close, and talk with the builders.

 

Dave

Houston

ive and uncomfortable to wear too.

 

Sounds like there is no comfortable solution other than pressurizing the complete interior of the plane with compressed air.

Just how high are you wanting to take your unpressurized, piston powered aircraft?

 

You can wear a mask with high concentration oxygen "comfortably" into the lower flight levels and be able to breathe normally.

 

If you are observant you can even get an MBU regulator, mask and blinker off ebay or from a surplus store.

 

Dave

I don't recall the exact number, but I seem to recall that you do not want to pressurize the human lung by more than 1.5 to 2 psi, as it will easily rupture.

Since you guys have addressed the physics and pathophysiology of this pretty well, I am not going to waste bandwidth restating what has been explained at least twice.

 

My contribution will be to clarify the magnitudes (or lack of) involved in the lungs when they breath.

 

Sea Level atmospheric pressure is 14.7 PSI/760 torrs/29.92 inches of mercury.

 

If you were to take a glass column of mercury and hold it such that an open end of the column were in a bowl of mercury, and the sealed end was at the vertical end, the atmospheric pressure would push the mercury in the column to a height of nearly 30 inches.

 

Now.. Imagine we are using water.. the column of water would be 33.9 FEET of water.. 14.7 psi of sea level standard day air pressure would be THAT tall... even at say.. 10,000 feet, where you have 1/3'rd less atmospheric pressure, that column of water is 22 feet.

 

Now.. translate this to the ventilator patients I deal with on a daily basis in the intensive care unit. We measure airway pressures in CENTIMETERS of water.

 

The "otherwise healthy" average patient's inhalation pressure and exhalation pressure, UNASSISTED (there are vent modes that do this) are on the order of 20-30 CENTIMETERS of water.. When they have severe disease, it may take pressures of 60 or more CENTIMETERS of water to force air in... when they cough it may reach 100 CENTIMETERS of water pressure. This translates to less than 3.5 feet on a water manometer in a worst case scenario and is less than 1 foot in normal breathing. This translates to 0.44 psi at sea level.

 

The body deals poorly with large differentials in actual pressure. More than about 1 psi and you cant hold your breath against the air trying to leave your body.

 

To address the original poster, you cant simply pressurize the mask to successfully breathe AIR at high altitudes.. and in the case of VERY high altitudes, you cant use pure ox in a pressurized mask. You have to pressurize the entire pilot - either a suit.. or a cabin.

 

As Marc and Waiter have already addressed, its all about the pressure imposed by the oxygen content in the inspired air.

 

Dave

David,

 

Thanks for the reply. You may be the one to ask about my two stage cooling system I had written on an earlier post.

 

I was wondering why we couldn't use a two stage radiator system.

 

You can, but from what I've been told it wont work as well.

 

What you are describing is having the rads in series. You will get less heat out of the system (from what I have had described to me) doing this, as compared to having both in parralel with each other, both ducted to have airflow going over them. You can put the fan somewhere ELSE with a very weak spring and hinge on a large flapper. Turn the fan on when on the ground or at low forward speed, and if the ram air isnt strong enough to blow the flapper down, the fan will force air over the rads.

 

I am using two Goldwing M/C rads. Each was designed for a 1100 cc M/C engine. Each comes with a 12v fan, and I will likely find a way to use them. I plan to mount them in parralel. This splits the water flow between the two rads, slowing it down, allowing it more time to transfer heat to the air. Each rad will also have the hottest possible water going into it, so that you can therefore transfer the greatest amount of heat.

 

The radiator system should be a closed pressurized system with at least a 16 lbs radiator cap. It will also need an overflow tank mounted on the firewall. A closed system is needed because for every pound of pressure in the radiator system you reduce the boiling point by 10 degrees. This is why modern radiators are so much smaller now and not the size found in my '51 Chevy truck.

 

I hope you meant that every PSI INCREASES the BP of water by 10 degrees. Sounds nifty but keep in mind that Rotaries dont tolerate overheating well, and lose power/compression when this occurs. Granted, more cooling occurs through the OIL (up to 30% of it) as compared to water, but making the cooling system capable of handling more heat in this manner may backfire. Maybe it will work for you.

 

When taxiing on a runway the electric fan radiator thermal switch would switch on the fan keeping the temp reduced. It may not totally keep the temp at 180F but below boiling. When in the air the second airflow radiator would kick in keeping the temp at 180F and allowing the thermal switch to kick off the electric fan radiator. Keeping the electric fan out of the airflow would eliminate the air dam issue.

 

Again, there are ways to mount rads in the airflow without putting the fan in the way, yet still being able to use the fan. The big scoop on the bottom of the LEZ lends itself to having a large enough area for this. The LEZ's with the top cowl mounted scoops may be even better for this, as you can put EACH in the airflow. If you are building from new, you may even put an oil cooler in the nose, velocity style, to permit cabin heat from waste heat from the oil. You have lots of options at your disposal. Truth is, you will have to find what works best for you, and like some of the military folks around here can vouch for, no plan survives first contact with the "enemy".

 

I currently plan on using George Graham's three radiator setup if I have enough room under the LEZ cowl. This is detailed in Contact newsletter issue #62. He had a rotary race car driver give him a great tip on cooling. He said to ensure the hot water hose is connected to a radiator and not capped off because it will cause the rotary to overheat at high rpms. If this doesn't work I'll be forced to use the two stage system described above.

 

On the gas saving issue: Safety is the biggest factor for my rotary decision. If the rotary is a little higher in fuel consumption than the Lycoming, as you said earlier other benefits will offset the difference. Do you know the recommended TBO for a rotary?

 

I thought about overhauling the engine myself but changed my mind. I have experience in conventional auto mechanics but not with the rotary. I felt something as important as this should be left to the experts and is why I plan on getting Bruce to do it with the aviation mods.

 

Ed

Recommended TBO hasnt been established, per se. Highest time that I am aware of is about 1400 hours, and that is Tracy Crook's. He is flying a Renesis now, so the old engine was REPLACED but not because it NEEDED to be. I did some math a ways back, and 2000 hrs engine time would have been 110,000 miles at highway speeds in a car (but not at the same RPMS, etc).

 

I can appreciate the hesitation regarding your own overhaul, and if you choose to let Bruce do it, thats fine. He will do it RIGHT. A local "expert" may not, as John Slade can attest to (he frequents elsewhere, but his website is www.canardaviation.com). But, if you arent going to port the engine, know how to follow instructions to the T, and how to read a micrometer, and how to use simple tools, you should be able to do a rotary overhaul yourself. It will be a big confidence booster and also will validate the skills to do your own repairs in the future if needed. Nothing like knowing it was done right cause you did it yourself. Bruce sells a tape that breaks it down. The main "aviaton mod" doesnt involve overhaul, and involves replacing a thermal pellet valve in the hollow e-shaft with a slug.

 

Good luck,

Dave

Swinn -

I've had an on and off mood about the Rotary because they're hard to keep cool. I may have found an answer to the cooling problem with a two stage radiator system. I'm awaiting a reply from Paul Lamar who is currently evaluating it.

 

I've been away from here for a while, but saw the rotary comment and wanted to chip in my 2 cents. I apologize if this is a stale thread.

 

Cooling on the rotary isnt a problem if you use enough radiator area and have enough cooling air flow. Thats what the "problem" is. Pushers have it extra bad because the prop blast isnt blowing over the air intake, and cooling air flow only occurs with facing into the wind, or with forward motion.

 

I contemplated dual rads as well, in "series" which I am assuming is what you mean by two-stage radiator. Cooling is a function of CHANGE in temp.. "Delta T" in science lingo. You get the most heat rejection by having hot coolant going across a rad with cool air.. sounds intuitive... but if you put two rads in series, the first one will cool ever so much, then the second one will not have nearly as much effect, because the hot coolant is already "pre-cooled".. not as great a change in temp, so not as much heat is lost/rejected.

 

Conversely, having both rads plumbed in PARRALEL allows the water flow to be split between two rads, slowing the coolant velocity through each rad (each rad handles half the flow (compared to a series installation, with equal sized rads). Each rad has the coolant for a longer period of time due to the slow flow and each rad has HOT coolant with the greatest delta T compared to the cooling air.

 

Good luck with what Paul L can come up with for you. No disrespect towards him, but there is ANOTHER rotary oriented forum, called the FlyRotary list, its a true list serv, and Marv, the moderator, rarely intercedes. He doesnt delete or edit posts like Paul does, when you say things he doesnt agree with. The FlyRotary list is where most of the folks are who are FLYING rotaries. Pauls list has lots of theory, Flyrotary has lots of practical experience. In my mind, one practical test beats an analysis ANY DAY. Dont get me wrong.. He's a smart guy and much of his material is useful.

 

I unsubscribed from Paul when I went to the Reno air races and havent bothered to sign back up. If you want, flyrotary can be subscribed to at http://mail.lancaironline.net:81/Lists/?Language= and that link will let you link to the web archives. Check it out, you might be surprised what is there.

 

The most important factors about the Rotary is there are only three moving parts and the high power to weight ratio. A 13B rotary normally will produce about 160 hp but will put out as much as 200 hp with a little tweaking. The weight (including the re drive) is a little more than what a 320 would weigh. The new Renesis rotary (improved 13B) found in the RX8 sports car will put out 240 hp with normal aspiration and has a 40% increase in fuel economy over the old 13B. I would like to see around 140 to 160 hp in the Long EZ.

 

The three moving parts is a big plus in my mind, but keep in mind that most of the problems that have occured with the rotaries have been the DIRECT result of inadequate or substandard accessories attached to it. Even though you have a car engine, I recommend aircraft or racing style craftmanship: hoses and fittings, safetywire, aircraft or race quality filters.

 

I also must say the 240 hp mazda claims its Renesis is putting out is probably inflated. Much of the "magic" is a direct result of a tuned auto intake and tuned exhaust, neither of which will be practical for aircraft use. You will have to fabricate your own intake and exhaust, and in all likelyhood a user built one will not be tuned to optimize power. Turbocharging can make up for this, even a light turbocharging, but the renesis makes part of its additional power by using 10:1 compression rotors (significantly higher than the earlier gens) and the high compression arrangement is less suitable to turbocharging due to a narrowed detonation margin.

 

The 40% increase in fuel economy has to be straight out of a mazda promotional book, and considering car performance is at much lower power than where the plane will be running, I dont consider that a credible value. Essentially the car will idle and make low power more efficiently. The Brake Specific Fuel Consumption of the NA older gen rotaries is in the .50 range (.5 lb/hp/hr) compared to .45 in a NA lycoming and about .55 in a turbo 13b. Yea.. thats right, the lycoming is actually slightly more fuel efficient than a rotary, but you can offset that cost by using car gas, getting tax rebates, and having cheaper overhaul and replacement costs. The rotary is slightly less efficient than a Ly/Con.. but your rotary operating costs are significantly less.

 

In case I have been vague about my leanings, I am PRO-rotary, 100% but I consider it a disservice if I dont present the bad with the good. How can someone make a truly informed decision if all they see are the good things, and are oblivious to known difficulties.

 

I am contemplating engine startup within 30 days or so, 2nd gen 13B, rebuilt by me, using Bruce Turrentine's rebuild kit, Tracy Crook's RD-1B PSRU, his EC-2 Engine Controller and EM-2 Engine Monitor. I have a custom intake of my own design, and will use the stock throttle body with modification. Normally aspirated to begin, and will add a turbo as able. Using a 3 blade IVO magnum electric inflight adjustable prop.

 

Dave Staten

And don't forget, twice the risk of failures.

 

Waiter

I disagree, in that the above statement "can" be correct but it is misleading in that vein.

 

If you want to play with statistics, lets play with statistics. The risk is not additive, as you suggest. The risk of any one engine failing is independent of the risk of another engine failing (barring some freak mishap that causes the simultaneous failure of both engines - such as fuel exhaustion, volcanic ash ingestion or parts of one engine impacting the second).

 

Yes, there are now two sets of "points" that can fail as compared to a single engine aircraft, but barring obvious sources of double failure (which would sideline a single engine plane too), you are actually less likely to have a total power loss.

 

The risk of a double failure due to non-coincident circumstances is the product of the two risks multiplied against each other..and since both are already fractions/decimals already, the product equates to a smaller risk of "total engine failure" than a single engine product of the same type. A 1% risk of failure in each engines results in a 0.01% chance of simultaneous failure (excluding common causes, again)

 

Much of the "trouble" with certified light twins is that they are usually not well-powered enough to operate suitably on a single engine after failure. The reason is that the Feds (FAA) didn't/doesn't require it for the light twins to be certified. That unfortunately results in a certified light twin having just enough power to take you to the scene of a crash

 

Compare this to transport category twin engine aircraft.. They have a "good" single engine rate of climb compared to light twins. The Learjet I used to do medical stuff in the back of, could climb at 1000 fpm with one engine out... and over 5,000 fpm with both turning, and the nose yanked up.. I'd gladly have a twin engined plane if it was affordable for me... but it would have to be a safe design as well.. and some of the things that would make it safe make it unaffordable for me.

Is it possible to mount two engines on a cannard design in a manner where the yaw produced by a "low, slow and heavy" engine loss won't present significant risks? I suspect that it is possible.

Way you have directional stability is to 1) not have asymmetric thrust such as a Rutan Defiant... or 2) have enough airflow over vertical stabilizers and rudders to provide enough control effectiveness.

 

The minimum indicated airspeed at which this control effectiveness with asymmetric thrust is called Vmc, and when you obtain your multiengine rating in certified planes, you demonstrate flight approaching Vmc as part of your training. This control effectiveness is reliant on a minimum velocity over the vertical stabs.. One way to augment that is to have twin tails in the propellor slipstream like the Beech 18.. the other is simply to go fast(er). Using a pusher, without a tail surface mounted behind the engine, the answer is brute airspeed.

 

When flying a light twin, your best rate and angle of climb speeds are usually WELL below the Vmc (indicated by a red radial or "red line" on the ASI). For the safest operation, you rotate, clear any obstacles and then lower the nose and accelerate past Vmc/Red Line, then to Vyse (Single Engine Best Rate of Climb/Blue Line). Doing this in a canard twin with the potential for asymmetric thrust simply takes time and distance. Dont plan on short fields with lots of obstacles.

 

A twin, by the way, will likely double to triple your operating costs. Twice as many engines burning fuel... prudence would dictate a propellor system that is featherable to make an engine out a workable event.. and those arent cheap...to buy nor maintain. You are adding a level of complexity that may not be called for. If you want dependability, go with a turbine or turboprop installation.. by the time you get two engines, ECU's, propellors, and everything put together, you can get better reliability from an adapted turboprop app. for not much more cost.

 

Dave

Today I tried to put my "money where my mouth is" and it appears that the "Fuelman fuel card" approach is not going to work for me.. not enough projected volume and they actively discouraged my application. I followed up with Chevron/Texaco.. the most likely brand to be used locally.. and their fleet card setup does not allow for what I was envisioning. It appears that what I was describing (with the tax removed on the front end) was something these card services only offered to governmental entities (such as the fire dept I was working for).

 

I did some additional digging and it appears that from a FEDERAL standpoint, for PERSONAL use there is no deducting the 18.4 cent/gal federal excise tax on gasoline. There are specific conditions that DO apply to both autogas and Avgas that apply to certain business and nonprofit situations (flight schools??). The Federal Guidelines can be found at http://www.irs.gov/pub/irs-pdf/p378.pdf

 

The STATE portion of the fuel tax.. 20 cents/gal in Texas, however, appears to be WHOLLY refundable if autogas is used in an aircraft. I will be subject to recordkeeping requirements with regards to an audit trail, but essentially I save my reciepts and fill out a reimbursement form and submit to the state comptroller. This actually works to my benefit since I can get the best fuel deal available (within quality limits) and then get the refund on top of that. Your state may vary.

 

I envision having a credit card used SOLELY for fuel and or airplane use, perhaps a "one card" fleet card system that can give a detailed reciept. I might be charged a few cents/gal for this priveledge but even 20 cents / gal discount is significant.

 

I will mention this to one of the local flight schools who has been running mogas in part of their fleet, and been paying cash at the pump into their transfer tank.. he may be able to claim both state and federal taxes.. and he uses at LEAST 100 gal/day mogas.. thats over $10K in combined tax load he may be able to get back.. I know he could use the help, and maybe his tax man will agree that its kosher.

In most auto engines lead can do two things: Coat sensor components and alter their performance; render the catalytic converter inoperative.

 

The old lead acted like a lubricant and octane enhancer in bygone years. Over all, if the stuff does not kill the seals or instrumentation I believe the engine will do just fine.

Aircraft use of automotive engines at this time are exempt from the use of catalytic converters, since they are "off road" and not licensed for use on the public roadways. So, no worries about using 100LL from that standpoint.

 

The other biggie is the coating of the oxygen sensor in certain EFI engines There are some high dollar O2 sensors that are resistant to this effect, and there are some EFI's that do not utilize an oxygen sensor to determine mixture (Tracy Crook's EC2 being the primary example in my mind, but there may be others). Some EFI's use the sensor for "setup" and once set no longer require an O2 sensor. So, that issue is not a biggie either, if you plan for it from the beginning.

 

Lead fouling of plugs can be a problem, but i believe there are scavenging agents available that can help with that problem. Also, simply having a well adjusted mixture can prevent the buildup of lead deposits (just in the same manner that you lean during taxi to prevent fouling with lyc/conts).

 

Fueling logistics present a valid issue: Mogas is not routinely available at airports. At the few airports that it IS available, its not that much cheaper than Avgas (ON FIELD) except in a few isolated locations. Airnav is not a good source of who really has Mogas, since SOME fields show it as available on search, but closer review shows that its not available on the field at the FBO.

 

However, looking at the mission profile for the Velocity I would anticipate that much of our flight will be within the round trip capabilities of the aircraft. That eliminates fueling out. I will gladly pay a ramp or tie down fee for the gracious use of someones facilities, if I am not inclined to buy their fuel. On the cases where we have to fuel "out", Avgas is not incompatible with the engine's innards (we aren't using an oxy sensor) and can mix without issue.

 

Something I am contemplating but have not had a chance to discuss with Chris Barber just yet (remember, I'm doing the engine for his plane) is the possibility of obtaining a Rushce/Fuelman type card account, and a few rubberized bladders (similar to transfer tanks/ferry tanks). This card account is a fleet fueling account system I used to use when I worked in EMS and Fire Depts. Its not limited to one brand, and its pretty universally available. I am already considering the installation of a transfer tank in the bed of my pickup truck for fueling the aircraft and would need to plan on a fuel card system of some kind anyways. In my case, most of the LONG trips I would be taking would be overnighters or longer, usually to see somebody I know, and it would not be a big deal to use a few small (10 gal) collapsible transfer tanks to get fuel from outside the fence and bring it to the aircraft. Once empty, roll em up and stuff em.

 

I admit it sounds like a bunch of work. But.. Super U/L costs $2.00 a gal in Houston. It wont take a lot of fuel purchases for this system to pay for itself with regards to Avgas. On a tight schedule? In a hurry? Racing the Weather? Then screw it, and get the blue stuff.

 

The reason I keep mentioning a fuel account of some type comes back to one key issue: an airplane is an "off road" vehicle. It is not licensed to operate on the roads. Therefore it's fuel does NOT need to pay state and federal fuel tax. When I set my former vol fire dept up on a fuel card account, the sales rep told me that any off-road engines could be fueled tax-exempt: generators, separate pumps (not part of the fire engine..etc). In Texas that amount comes to 38.5 cents per gallon. So, Super unleaded into the plane at a current cost of $1.60/gal.

 

Transfer tanks can be as simple as some plastic marine tanks in the bed of a truck, to a 50 gal metal tank with attached pump, nozzle and cover. Stay under 55 gals unless you want to bust DOT rules (CDL, placards, etc). Tanks over 55 gals must be plumbed into the fuel system of the transporting vehicle as "aux tanks".

 

So.. how much convincing do you need to be able to fuel your plane at your HOME field for $1.60 a gal and still be able to use the existing 100LL infrastructure when you must?

 

Sorry for the long winded diatribe.. its what Im good at.

Dave

David,

Thanks for the concise explanation and everyone else on fuel mix. I can now see why people remove the oiler.

 

My other question is what does Jon Slade use? Also, how do you add the oil? A little at a time or just dump it in and fill?

Slade premixes in the fuel tank. And I do not have any idea just yet how he accomplishes the mix. He has a contact link on his webpage at www.canardaviation.com.

 

Dave

I did ask him about rotary reliability. He says they are reliable powerplants today and should have little problem running over 250K miles. Of course he is still using cars as a reference, I do not know how he would feel about them in airplanes.

 

What would be really interesting is to see just how much maintenance is actually performed and if someone can give service intervals on beasts.

250,000 miles at an average of 50 auto miles/hr comes out to 5000 hrs engine use.

100,000 miles at the same average comes out to 2000 hrs engine use

 

Typical aviation engine maintenance specifies oil change at every 50 hrs(2500 miles auto equiv at highway speeds).

 

100 hr inspections come out to 5000 auto miles equiv. This would be a good time to lube up everything, check compressions in the combustion chamber, check the coolant system. Check the belts and hoses. Inspect the plugs. Check bolt torque, look for cracks anywhere.. etc.. standard things that an aviation engine would be looked at.

 

If you dont hit 100 hrs in a year, then at LEAST do the "100 hr" annually. At 100 hrs a year, or even 200 hrs a year, you will have to take 5-10 years to hit "100,000 miles equivalent"

 

First, It is my understanding that many rotary engines tend to have sealing problems that get worse with wear and turbocharging.

-- Len

Rotaries have tight tolerances. When new they should meet those tolerances. When rebuilt, you need to mike out everything and make sure its in spec. The factory engines were limited to first 8, then 10 psi of boost. 8 psi is comparable to 45" manifold pressure (speaking in aviation lingo). These limitations were to improve reliability and limit the damage a kid with a lead foot could do to the engine. As with anything, the more power you develop the more wear occurs. The sealing probs are a combination of several things - carbon fouling from poorly burned injection oil causing wear, detonation from using low octane gas for high power performance, disabling turbo boost limiters, etc.

 

 

What is the typical automotive life of one of these engines?

-- Len

The Jspec engines are replaced at approx 40,000 miles (100,000 km), an arbitrary number set by Japan for emissions reasons. American engines with 100,000 miles have been reported to be junk. BUT.. remember.. these are running stock oil systems and the carbon fouling is a major cause of wear.

 

I myself had a twenty-year-old diesel Benz ... The anecdotal evidence I've seen does not indicate that rotaries can come close to touching these for reliability.

 

Because of the power to weight ratio, I would like to use a rotary, but I am not convinced of the ease of maintenance or reliability.

-- Len

Diesels ARE a wonderful thing..durable, powerful and LOTS of torque... but when I went to Oshkosh 2 years ago, Theirlert or SAE or whomever it was there said "our engine wont work on your plane" and Deltahawk was saying "next spring" for the fifth or more summer in a row.. they joke that one year that prediction will come true. Diesels can burn Jet A, which is in NO danger of going away in the near future, and is not as refined as avgas, and not nearly as pricey. he diesels are also being priced in the >$25,000 range at a minimum. Comparing a gasoline rotary engine to a diesel is not a fair comparison. That being said, if the diesels were readily available for our application (we want to be airborne within 6 months) then we would have considered it. I must say when I met Chris, I was DEAD SET against auto conversions in aircraft. Chris prompted me to look at the rotary, I did my homework and can understand how the rotary, while not perfect, is a much better/more reliable source in my opinion than a horizontally opposed, air cooled, reciprocating aircraft engine.

 

There are a few folks out there with hundreds, even over 1000 hours on their rotary engines and are flying... Ed Anderson and his RV-6. Tracy Crook and his RV-4, building an RV-8 with a renesis). Dave Leonard and his Turbo RV-6. John Slade just started flying his Turbo Cozy Mark IV. I will say that most of the probs with flying rotary engine airplanes appear DIRECTLY related to using the stock automotive turbo in an aircraft application (OR.. to improper rebuild..even by alleged engine professionals). I would recommend a low pressure/high output/High A/R turbine/compressors. I am still working out the details on what aftermarket turbo to install on our (chris and I's engine) and I want to see how Dave Leonard and John Slade do with their latest turbo incarnations.

 

If you dont want to build your own, I would recommend Bruce Turretine as a source for a rebuilt, "complete" powerplant (rather than using a local engine guy). he is considered the "go to" guy in rotary aviation circles, and sells many of the parts needed to do a rebuild, as well as a fairly decent "how to" video.

 

Dave

Thank you very much for the explanation! This is definitely helping me to wrap my brain around Wankel engines.

 

Now more questions. So how much does this improve the life of the engine? How much oil needs to be added to the gas, and is it available at most airports? Does this mean that there is no oil in the crankcase, or whatever you call where the crank passes through?

-- Len

The standard "mix" as I am hearing others use is 120:1 ratio.. this is approx 1 oz of oil to a gallon of gas.

 

Remember that the stock rotary injects and burns CRANKCASE oil that it siphons off the pressurized oil system and places in the oil injection system. A diagram of the oil system is depicted in the Hayes Mazda RX 7 manual. The oil that is used in the crankcase is NOT intended to be burned and is NOT clean burning. The resulting soot/carbon deposits from this BURNED injected crankcase oil is one of the leading (as related to me) causes of wear in the Mazda 13B engine. This soot builds up in the apex seal grooves and causes the seals to not be able to spring back and forth properly, causing increased wear, loss of compression and the such. Mazda chose to go with this system instead of adding a 2 stroke oil tank plumbed separately for apparent marketing reasons (what do you MEAN my $40,000 sports car has a "two stroke" engine in it, and that I burned it up by not keeping that oil tank full"???)

 

Two alternatives are presently kicked around... The easiest is to simply remove the oil injection pump, the injector nozzles and their air tubing and simply add 2-stroke oil to the fuel in the prescribed ratio. There is a margin of error here depending on how much fuel you add and how much oil you add, but I should think erring on the "too much" side in oil quantity is not as critical. For a velocity with a 60 gal fuel load, thats 2 quarts or so of oil for a fill up of gas. Carry a gallon with you at all times and you can fly a full tank away and a full tank back and not have to sweat finding it at the FBO. If you need it bad, you can take a crew car to a 24hr Walmart and get SOMETHING to get home on.

 

The more complex but "purist" approach is that taken by the racers. They use the stock oil pump but have a diverter that siphons oil from a separate gravity feed tank filled with clean burning 2 stroke engine oil. The pump controller in stock form is linked to the throttle linkage, so full throttle = full oil injection. I am hearing that people flying with this type of oil injection are disabling linkage (which would be complex, if practical at all - custom intake systems) and wiring the pump in the 3/4 to full open position. This doesnt really cause a problem, since the majority of aviation flying is at a steady, high power setting, so the oil flow is being permanently set to match the average power setting. For the Velocity that Chris Barber is building (and I am rebuilding the engine for) I figured that a 5 quart tank on the firewall would suffice (a full tank of fuel to fly away, a full tank to fly back, and half a gas tank's worth of reserve injection oil)

 

In using either of these alternatives, the passage from the engine's oil system to the oil injection system is plugged, and the engines oil system operates normally otherwise. Keep in mind that the "oil injection pump" is a separate beast from the "engine oil pump". Roughly, oil flows from the pan, to the "engine oil pump" to the oil cooler, to the block and oil filter, THEN is distributed to the rotors, shaft, turbo and bearings, before falling back into the pan. If properly built and not abused, using the separate oil injection system should result in MINIMAL to NO engine oil burning and as a result you shouldnt need to top off the engine oil in the pan regularly, rather only need to change it at regular intervals.

 

Chris Barber, who posted a few posts ago, had some links to follow. Some of these will lead to a WEALTH of information, both practical and theoretical on the wankel/rotary engine in aviation use. Biggest benefits of the rotary appear to be minimal vibration (compared to aviation engines), overlapping torque pulses (again, less vibration), only 3 major moving parts (no cams, valves, lifters, rods) and few catastrophic failure modes. I am aware of a few engine failures with the rotaries (which I attribute to growing pains, such as testing turbochargers) and so far all of them were able to develop partial power until landing.

 

I am rebuilding the engine for the Velocity project after doing lots of research, have access to the Hayes AND mazda shop manual, have the tools to measure out all the tolerances, and am replacing ALL the seals/springs/wearables. By using 2 stroke oil, I am hoping that come time for the next "rebuild" that there will be minimal carbon fouling found when we tear it back down. Not even sure what to plan on.. we will follow compressions and not rebuild until needed.

 

Total cost for the engine so far: $700 for THREE used J-spec mazda 13B turbo engines (without turbos.. jspec means approx 40K miles and REMOVED from service). A factory new renesis RX8 engine would be about $5500. Few hundred $$ for tools that I did not already have (air tools, dremel, engine stand and hoist come in handy). "Master rebuild kit" with seals from Bruce Turretine or Tracy Crook $900 range (yet to be bought). Count on another $2000 for EFI/engine monitor and another $3000 for a lightweight PSRU (gearbox... engine runs 6000 rpm, prop runs 24-2800 rpm). Contrast this to a 200 hp lycoming costing NEW > $25,000.

 

Also, running auto gas at whatever its current cost is (usually a $1/gal less) than avgas. You can add a lead scavenger soln to the fuel tank if you have to fuel with avgas away from home. You can use www.airnav.com to find autogas vendors on airports.

 

Hope I gave you some good information.

Dave Staten