Marc Zeitlin

If you read my statement carefully, I said that the designer of the airfoil BELIEVES that the critical Mach # for that airfoil will be around 0.5, or 346 mph at 25K ft. It could be higher, it could be lower. It's doubtful that it would be as low as 300 mph, and I never said that there's a problem at 300 mph TAS. No, what I said was that for the sake of having some safety margin, Richard Riley __recommended__ that 300 TAS be Vne or Vmo, whichever you'd like to call it. Berkut claims a top TAS of about 300 mph - no Berkut will INDICATE 300 mph - more likely about 260 - 275 mph, but that's a guess. I do not know exactly what airfoil the Berkut uses, either for the canard or the main wing - I do know that they do NOT use the same airfoil for the main wing as the L.E. and COZY. The issue here is with the specific Roncz airfoil used for the canard of the COZY aircraft. Please list all the other certified/homebuilts that use this airfoil for flight over 345 mph before making such cavalier statements about safety issues...... Jim, others, See: http://142.26.194.131/aerodynamics1/High-Speed/Page2c.html for more information on this phenomena. I thank Richard Riley for pointing me to this reference. With respect to other questions, sweep in the canard, or a different airfoil MIGHT ameliorate the situation to some extent, but the factors that make this a good airfoil for a canard aircraft make it bad for "Mach stall", and the factors that give other airfoils a better "Mach stall" number make them poor performers as a canard airfoil in our type aircraft. Everything's a tradeoff. New airfoil or sweep - it's not even close to being a COZY anymore, and you better be an aerodynamicist..... With respect to Jim Price's L.E. - the fact that he went to 35.5K ft. with a 135 HP engine makes it even more amazing :-). Realize, of course, that he was not at gross weight, and that service ceilings are determined (at least in certificated aircraft) at maximum gross. I don't know if the AeroCad/COZY service ceilings were determined at gross weight, but that's how they SHOULD be quoted. To Evan's question, a normally aspirated COZY MKIV with a fixed pitch prop won't get close to 200 mph, much less 346 mph TAS at 25K ft. Some are proposing substantial power increases by turbocharging and/or substantially larger engines, and using CS props, and then the answer seems to be that 300 mph at that altitude should be achievable. Hence the warning.

The question was asked "how high can a COZY go?". Jim Price has taken a normally aspirated 160 HP Long Eze to over 35,500 ft., and holds the altitude record for that weight class of single engine piston aircraft. Vance Atkinson has taken his 160 HP COZY III to 23K ft and performed a stall series there. His TAS was 152 KT at full throttle. Aerocad claims a Service Ceiling (100 fpm climb rate) of 25K ft. with a 200 HP engine. I have some vague recollection of Nat stating 26K ft. service ceiling for the COZY MKIV, although I can't find a reference. With respect to top speeds, the Roncz canard is suspected (by John Roncz, the designer) of having a critical Mach # of about 0.5. At that point, the canard will Mach stall, and the plane will become an uncontrollable lawn dart (per discussions with Richard Riley - one of the former principals in Berkut Aviation, the fastest homebuilt canard). 0.5 Mach is 380 mph TAS at sea level (we don't ever have to worry about getting there). However, at the altitudes that some people are talking about, say 25K ft, 0.5 Mach is 346 mph. Notwithstanding flutter considerations (which a simple web search, left to the reader as an exercise, will show is dependent both on TAS and IAS), this critical Mach # is one limit that you do not want to get near. Since 200 mph IAS is ~300 TAS at 25K ft., that's not far away from 346 mph - a short dive to change altitude, or a distraction and small stick bump could easily lead to a large speed change in a short period of time in these slippery aircraft. Mach stall is unrecoverable, unlike a short stint above Vne, or even a short stint with flutter. In either of the other two cases, throttle reduction and/or stick pressure will reduce speed and most likely eliminate the problem. Once Mach stall occurs, the nose drops, the speed builds, the Mach stall gets worse, and as RR has said, you tie the low altitude record while pointed straight down. RR believes that no aircraft using the Roncz canard should use a number higher than 300 mph TAS for Vne. Since no COZY's now exist that can reach this #, the 220 mph IAS Vne has proven acceptable - if people put substantially more speed capability into their aircraft, such as Greg Richter, or some of the posters here, Mach stall will become a large factor in their considerations. Just thought this might help some people in evaluating their options.

All known COZY builder websites are available at: http://www.cozybuilders.org or: http://www.maddyhome.com/canardpages/main There are many overlaps.

The Vne and Va number I quoted were from the COZY MKIV manual. I will not presume to state where Nat got those #'s from, but the Va (which is what we're interested in here), seems to match up with the 3.8 G limit for Normal Category aircraft, as verified by the performance numbers of my plane in particular, and the published performance data from Nat's plane. The only issue I have is this 180 mph number, and it's relation to the 6 G figure. I have no clue where this 6 G limit came from - I don't ever remember seeing it in the owner's manual, or anywhere else, for that matter. If you've got some reference for that, I'd be very interested in seeing it. Personally, as a LIMIT LOAD #, I'd use the Normal Category limit of 3.8 G, which is what Nat seems to be recommending by his claim of 140 mph as the Va.

Normal is 3.8 G, Utility is 4.4 G. Yes. And I to be more accurate in my statements. The lack of face to face interaction makes it easy to misunderstand and get bent. My raison d'etre is gone.......

I've deleted all the stuff we agree on - let's continue: I am familiar with Vn diagrams, and they are available for GA aircraft. After a night of pondering, I agree that you are absolutely correct here - up to Va, you need airspeed to achieve a certain G loading - I missed that in my previous analysis. I'm not sure where that 6G comes from. I did some calculations from the stall speed and wing area on my plane, and here's what I come up with: Wing area (including canard): 110 ft^2 Max average Cl: ~1.4 Weight for calcs: 1800 lb. These come from a stall speed of about 72 mph at that weight. Given that (at Sea Level), the Vn curve below Va for the COZY looks like: 0 degree bank - stall speed ~72 mph - 1 G 60 degree bank - stall speed ~96 mph - 2 G 70.5 degree bank - stall speed ~126 mph - 3 G 74.7 degree bank - stall speed ~142 mph - 3.8 G 80.4 degree bank - stall speed ~180 mph - 6 G Since the Va of the COZY is about 140 mph (IIRC), I've got to assume that Nat picked the 3.8 G from the normal category of certification to get his Va. If Va was 180 mph, then 6 G would be the limit. Anyway, given this info, increasing speed up to 140 mph will, as you said, give you the tightest turning radius - from ~125 m radius at 2 G to about 110 m at 140 mph and 3.8G. Bingo - pretty good guess :-) - or did you calculate that? Now, at any speed OVER 140 mph, your radius will start getting larger again, since you're not allowed to pull more G's. So, for the conditions postulated (SL, any amount of power needed), Va will give the tightest radius turn. Of course, the COZY can't maintain 140 mph banked at 74.7 degrees in level flight even at SL, so it'll never get this good :-). The book I mentioned previously, John T. Lowry's "Performance of Light Aircraft", has some excellent explanations and graphs of maneuvering performance of GA aircraft taking power and altitude into consideration, and has some good examples of how to get yourself into trouble in a climbing narrow canyon..... Better that than violent disagreement :-).

This much is true. I don't know what you're remembering here, but it isn't your physics or flight dynamics. The radius of a level turn is: R=V^2/a Where "V" is the velocity and "a" is the acceleration. Doubling your speed will quadruple your radius, and doubling your "G" loading (acceleration) will halve your radius. You had that backwards. Sorry, but it is NOT so. Assuming you have enough power to maintain level flight, your minumum radius turn (level), as shown by the equation above, will occur at the MINIMUM speed with the maximum acceleration. I guarantee you that in a canard aircraft (or any aircraft, for that matter, that you're willing to fly at stall speed), flying at the maximum bank angle, stalled, with the stick all the way back, will get you the minimum turn radius. See Page 260 - 264 of "Performance of Light Aircraft" by John T. Lowry for graphs of the turn radii of a Cessna 172. It is obvious from looking at these graphs that flying right at stall at bank angles of 60 degrees or above AT THE MINIMUM POSSIBLE SPEED) will get you the minimum radii. He discusses the power needs as well. This makes no sense. AOA determines G loading. Instantaneously, you can pull whatever G loading the elevator authority will allow, and it will last for however long the power available will let it (or else you'll start down). If you can pull 6 G's at 160 Kt, you can do it at 130 Kt, and the slower speed will have a smaller radius. Instantaneous G loading is not dependent upon speed - I can do a 60 degree, 2 G turn at any speed above 85 mph (canard stall) in my plane. I can't MAINTAIN it for very long at anything over 100 mph or so, but I don't need to to do a 180. At any rate, if it takes 2 seconds for me to roll to 60 degrees, and I maintain that at 100 mph, I've got about a 125 m radius turn. Having practiced these many times, I can tell you that it looks like I'm spinning on the inner winglet.

Yes. When I was at Bose, I worked on the Bose X noise canceling headsets for pilots, as well as the first generation of noise canceling headsets for the mass market (they're now selling 2nd generation mass market headsets). Noise reduction headsets (called ANR, for "Active Noise Reduction") have been around since Bose invented them about 18 years ago, but only recently (5-10 years) has the price on many of them come down far enough for them to become very popular. I have a pair of Bose ANR headsets, a pair of Lightspeed ANR headsets, and a couple of Peltor passive headsets. The Bose and Lightspeed are great - I won't wear passive headsets anymore - the Peltors are only used for the rare times there are people in the rear seats. The Bose X were the best headsets when they came out in 1999 - I don't know if that's still the case, but they're certainly still the most expensive :-). They are VERY good in the COZY - any ANR headset is better in any plane than any passive headset. Pretty good guess, for not an engineer :-). There's a tiny microphone INSIDE the earcup, as close to your ear as they can get it. It picks up all the sound that ISN'T coming through the wires, and the circuit board inside the earcup generates the same noise, but 180 degrees out of phase, so it substantially reduces the incoming noise. It doesn't actually cancel it, because the microphone would have to be inside your ear to do that (which would be uncomfortable), and because the technology only works at the lower frequencies - generally there's no effect on anything above 300-400 Hz. The Lightspeed Engineering website has an excellent tutorial on ANR headsets. See: http://www.anrheadsets.com/

See: http://web.tampabay.rr.com/chipmar/pods.htm http://web.tampabay.rr.com/chipmar/eze-thumbs.htm http://www.prekas.nl/longez.htm http://www.noaa.inel.gov/capabilities/LongEZ/ These were found with a 2 minute search on Google for EZ baggage pods. figure on a 5 - 7 kt speed loss.

Agreed. Not at all. It's just that he's more likely to get the information he's looking for if he asks a somewhat more specific question, that's all. That, and the fact that there are few people on this forum that CAN answer his questions, other than those that have already. No limit - just trying to maximize the information presented.

What, so you don't want any insulting behavior between members here, but it's OK to insult other "lists"? I assume you're still referring to the canard-aviators list, which had the characteristics you posit a couple of years ago, but since you're not on it, how would you know what it's like now? In fact, for the past 9 months or so, just about everything and anything has been discussed, since a new moderator came on board. You're way out of date. You've heard from Jim Sower, your hangar mate, me (in Ken Miller's back seat) - what else are you looking to hear about? Simple, positive G aerobatics are clearly doable, but the canard aircraft roll slowly, pick up speed too fast, and are generally not optimized for these activities. Is there something we've missed in this discussion? Ask a question about something in particular.......

I say that (directly from the FAR's): Part 23: Airworthiness standards: Normal, utility, acrobatic, and commuter category airplanes Since Amateur Built Eperimental aircraft are not certified in any of these categories, Part 23 clearly does NOT apply to our aircraft. Of course, safety would dictate that most of the requirements in this section are probably good ideas, and might be intelligent to use, but they DON'T apply to Amateur Built Experimental aircraft, and the FAA inspector/DAR CANNOT fail you merely for not complying with part 23. I don't know what that implies for who owes who $$$, but those are the facts.

I guess I was unclear on my question. I fly in the USA, not in Denmark. The regulations that Mike and I (and anyone else in the USA) fly in are not the same ones that are used in Denmark (even if Denmark has borrowed some from the FAR's). I was looking for: a) an indication as to whether Hank believes that a fuel shutoff valve is/is not required, and b) if he believes it IS required, whether he (or anyone else that believes it's required to pass the FAA inspection) can point me to a regulation (USA only) that states what equipment is required. We're only talking fuel system parts here - not instruments, etc. Thanks. P.S. - I now see that Hank has started another thread, so I'll move this discussion over there.

I'm not sure I understand - are you claiming that there __IS__ a requirement for a fuel cutoff, or that there isn't? Can you point me to a FAR, AC, or other FAA document that is clear on this subject one way or the other? Thanks.

Couple of reasons. The airfoil of the canard has a LOT of camber, and will not be able to generate the lift necessary, which is coupled to Mike's statement about not having enough elevator (although if you built in enough elevator travel, you'd probably stall the canard at almost any speed - it would be interesting [via CFD analysis] to see what range of speeds could be maintained inverted). I wonder if anyone has done that analysis...... Second, the fuel/oil systems are not designed/built for inverted flight. This might be remedied, but if the aerodynamics don't support it, there's no reason to build an inverted capable engine.

While you are correct that the canard family of aircraft is not considered "aerobatic", this isn't a good example to use of why. Rick Fessenden was pulling over 9 G's at low altitude and blacked out, causing a roll and the crash. It was NOT a function of the airplane doing something - it was G-LOC. Could have happened in any plane pulling 9 G's. Actually, that would be a good example of how well built these planes are, that they can withstand 9 G's on a regular basis - more than the pilot, apparently. At any rate, as John pointed out, any positive G maneuver is possible in the L.E./V.E./COZY aircraft. I've sat in the back of Ken Miller's L.E. while he did a 1 G roll, and if my eyes were closed, I couldn't have told that we were upside down. Loops, as John says, are NOT trivial due to the ease with which Vne can be exceeded. So, the answer is yes, simple aerobatics are possible, and as long as the G loading is kept relatively low, and always positive, a TRAINED pilot should be safe. No negative G's, no inverted flight, no whip/hammerhead/etc. stalls. I'm not trained, and I don't do aerobatics in my plane.

There's at least one. Marv Schuh's COZY III had 700 hours on it in 1995, and at some point he retrofitted the Infinity gear. There's a picture of his plane on the Infinity web site. Jim Marshall's MKIV has the Infinity gear as well, but I don't know if that plane has flown yet - I couldn't find an announcement in the newsletters.

While the winglets are about 7 1/2 feet tall, as LP says, the wings come off. You do want to make sure that you have the height available inside the garage, though, so that you can mount at least one wing/winglet at a time and work on it. The fuselage on gear is about 5 ft tall or so (not 4 ft.) so that won't be a problem either. As you surmise, the width __is__ an issue. If you have doublewide doors, you're fine. If you have single doors, getting in and out after you put the strakes on is a pain. If the diagonal distance is more than about 11.5 ft., it's doable with a substantial amount of finagling and twisting - if not, you'll have to tear the garage apart, or build somewhere else. You need to bring it out and back in twice to flip it over, and then out one more time, so the "tearing apart" must be repeatable. There are at least two builders and one flying COZY MKIV in New Mexico. AFAIK, none of them hang out on this list. If you're interested in contacting them, drop me an email and I'll put you in touch.

While there may be some advantages to the canopy (and I LOVE the visibility), just about the only thing I _don't_ like about my plane is how much of a pain in the neck it is to get in and out, especially for the passengers (front and rear). Gull wing doors and folding seats would be MUCH easier - I've tried on a Velocity, and it's nice. Everything's a tradeoff - get good visibility, maybe less weight, but the fit isn't great, it's a bit noisier, and getting in and out is a pain. With respect to the reclining seat question, the seatback and headrest support structure are part of the fuselage structure, and (at least according to Nat) are very important in the torsional stiffness of the fuselage. I would tend to agree, and that's NOT a change that I would make to my plane.

See: http://www.ez.org/cp25-p3.htm This is what the COZY has. Remember, the COZY weighs 600 lb. more than the L.E., which is why 6.00x6 tires and the other stuff would be better for the COZY on grass fields. Also, note that gravel and rough fields were still not approved - just average grass.

There are a number of issues. As you say, damage to the prop is one, but that can occur on crappy hard surface runways with garbage thrown up by the nosegear as well as on grass/sod/dirt. Some people will take off and taxi with the landing brake down on crappy surfaces to prevent this, and then retract it upon ground breaking. Another is the small size of the wheels - 5.00x5 are a bit small for lumpy surfaces. Doable, but not optimal. Some people have installed 6.00x6 main wheels, but this will entail larger and higher wheel pants, as well as more drag and a slight speed loss, as well as a minor adjustment in main strut length to account for the larger wheels. Eminently doable. Another issue is the marginal strength of the stock nose retraction mechanism. It just can't take much of a beating. With one of the electrical nose lifts, I don't think this would be a problem, as long as the casting area is beefed up with the normal set of modifications. I would also recommend setting the normal ground attitude of the plane a degree or two nose up, rather than at 0, to facilitate lifting the nose at slower speeds. There are some V.E. (Nigel Field, for one, IIRC) and other canard pilots that do/have operated from grass fields - even some small ones, but it's not very common. With larger mains, an electric nose, higher ground incidence, and judicious landing brake usage, a smooth grass runway should be no problem. I've operated off of a couple of pretty ratty paved runways (Jaffrey, NH for one) and the COZY tends to bounce a lot, but even with tight wheel pants on 5.00x5 wheels and the stock nose mechanism, it doesn't seem to be a major problem. I haven't hit any large potholes, though.

No, CSA only has indices online (put there by volunteers not associated with the newsletter, but with Terry Schubert's permission), not the actual newsletter. And by the way, Nat has never "put old copies on the web". All the newsletters that are on the cozybuilders web site were scanned, digitized, proofread, and put there by me, or by the volunteers listed under each newsletter. Nat gave me permission to do so, and restricted WHEN we could post them. ACS is now telling me that they'd like the newsletters posted as soon as they come out.

So where was I....But let's ignore that, and assume they're constant. Take a look at the "Range" graph at: http://www.cafefoundation.org/aprs/Cozy%20IV%20APR.pdf at 12K ft. You'll see that the range increases as fuel flow (and speed) decrease, almost linearly and monotonically. Also, look at the glide performance graph at: http://www.cozybuilders.org/performance/glide.html This indicates that at a weight of 1800 lb (let's use this as an average, in between gross weight at takeoff and minimum fuel weight at landing) you want to fly at 93 kt., or 105 mph. The graphs never indicate fuel flows at this speed, because NO-ONE ever wants to cruise this slow in a COZY - it's my downwind speed. I maintain this speed at 1500 RPM - I'm going to guess that this is 25% power or so, and maybe 3-4 gallons/hr., but that's only a guess. Nat claims that the fuel flow will bottom out around 5 gal/hr - see: http://www.cozybuilders.org/performance/cruise.html At that power rate, the engine is NOT very efficient, so let's assume that we've got to fly a bit faster to actually maximize the range - I'll guess 150 mph, since we already know that 50% power at 6 GPH at 12K ft. at 178 mph does NOT maximize range, given the CAFE foundation's graph, and that the fuel flow does NOT decrease much beyond that. Where does this leave us (we still haven't gotten to the wind part)? Well, we know that if we fly at about 150 mph, we'll probably maximize the range of the COZY, and extrapolating from the CAFE graph, I'm going to guess we'll top out at around 1500 miles with the standard tanks and VFR reserves. Now, that's 10 freaking hours in the plane, by which time __I'll__ be raving mad, and covered in urine, but maybe you folks can last longer in a tiny space than I can :-). Let's assume that we've got the max range speed now (well, close, anyway - it's gonna be somewhere between 105 and 150, but closer to the latter) - any faster or any slower will not get us as far. What about wind? Since we've got the part of the curve FASTER than max range speed, let's look at headwinds first - maybe a 30 mph headwind. Here are some datapoints: No wind (all approximate #'s, from the graphs and extrapolations): 150 mph 5.0 gal/hr 10 hours 1500 miles 186 mph 6.5 gal/hr 7.5 hours 1350 miles 195 mph 8.5 gal/hr 5.6 hours 1100 miles 186 mph 10. gal/hr 4.7 hours 875 miles With 30 mph headwind: 120 mph 5.0 gal/hr 10 hours 1200 miles 156 mph 6.5 gal/hr 7.5 hours 1170 miles 165 mph 8.5 gal/hr 5.6 hours 924 miles 156 mph 10. gal/hr 4.7 hours 733 miles We can see that there's a 150 mile difference in range between 150 mph and 186 mph with no wind, but for all intents and purposes they're identical with a 30 mph headwind. So, you don't gain anything by speeding up, but you don't lose nearly as much as you would have with no wind. Make it a 60 mph headwind, and: 90 mph 5.0 gal/hr 10 hours 900 miles 126 mph 6.5 gal/hr 7.5 hours 945 miles 135 mph 8.5 gal/hr 5.6 hours 756 miles 126 mph 10. gal/hr 4.7 hours 592 miles Now, we can see a definite shift to faster being better (but not by a whole hell of a lot). A tailwind will be a similar analysis, but going in the slower direction, rather than faster. Since we already know that we don't want to fly any slower, and we've got no clue what the datapoints look like below 150 mph, I'm not going to bother. So, what's this all tell us, for everyday flying? Basically, fly any speed you want - there's very little difference at low wind speeds in the MAXIMUM range you'll achieve due to speed changes based on the winds, or in the amount of fuel you'll use in that speed range. Fly at the speed that makes you comfortable and gets you where you want to be in the time period you want to spend. For REAL maximum range flights, such as record attempts or Hawaii - Mainland flights with minimum fuel loads, this type of calculation will need to be run with REAL numbers for low speed fuel flows and concurrent ranges. Graphing the results will give the most accurate answers, since getting a closed form solution for all the parameters together is non-trivial. Using a diesel engine that can be run at very low fuel flows efficiently would allow you to fly much closer to the best L/D speed, and get even more range. Let's extrapolate - if it took 2 gal/hr in a diesel to keep the COZY in the air at the 105 mph speed for best L/D, we'd be able to stay in the air for 21 hours - that would get us a range of 2205 miles. Even if it used 3 gal/hr at that speed, we'd have 16.8 hours and 1767 miles. Hope this helps, both with the concepts and the reality. And for Jim's response, it seems that the curves are/will be substantially different for jets than for piston engine propellor planes, giving different optima.

I have no idea where you got this definition from - it certainly doesn't have anything to do with the BRE. Maximum excess power will get you your maximum ROC (Vy), not range. Maximum range will come at a speed that is close to the maximum on the L/D curve (drag polar for the aircraft as a whole). It will also be dependent upon the SFC curve of the engine (to operate at or near max L/D, you'll need to throttle back, but throttling increases the SFC, so there's an optimum point that will be FASTER than the max. L/D speed) and also on the propeller efficiency, which also changes with speed. For Marc L.'s original question, this is all theoretical - he just needs to put in a diesel engine, which will increase the range tremendously by reducing the SFC. He then needs to fly up high at about 55% power, which with no throttle won't change the SFC much. Any differences in increased range that might be obtained by maximizing the BRE parameters will be unmeasureable in the real world with this plane, where the fuel weight is ~15% of the gross, as you point out. Again, for exact numbers, you'd have to know the SFC, prop efficiency, and drag polar curves for your plane (and none of us do). But let's ignore that, and assume they're constant. ---- Interlude for Physical Therapy appointment - I'll pick this up again when I get home tonight.

Correct on all counts. Another late night brain fart in unit conversions while typing quickly. However, the difference in Cl's is still minuscule - a few percent at most.