Richard Riley

Yes, I'm recommending it as a turboprop. 1) Far lower fuel burn 2) plenty of accelleration on take off 3) plenty of drag when you're coming down 4) cool turbine sound 5) good - not trashed - cores available. If your requirement is "Fly a cool looking jet" buy an L-29. It will be cheaper and safer in the long run.

Pure turbojets are great on the high end of the speed range, and are awful at the low end. F=M*A and when they aren't moving fast, they aren't Aing much M. Even the hottest modern fighters, the ones with a better than 1:1 Thrust/Weight ratio, take off with reheat (afterburners) on. You can get an engine that will run for that much, but I wouldn't stake my life on that engine continuing to run. It will be a run out that the military has junked, "overhauled" with sandblasting and paint. For a real zero time engine, add a zero to that price. If you want a turbine that comes remotely close to matching the airframe and you're willing to do it right, get an Allison 250. It will outperform the T-58 in every flight regime.

My biggest concern is the danger of overspeed - flutter, structural failure or mach stall. If you keep it below a realistic Vne, fine. That's what Greg Richtor is doing. But without the prop on the back making drag, when you're coming down the residual thrust and the clean airframe brings up your speed very, very quickly. We don't know what these planes will do if they hit critical mach. The canard might stall (lawn dart, death) or the main wing might stall (massive snaproll, probably over-G, but not pretty no matter how you look at it.) My second concern is the prodigious fuel burn. You don't get much range OR time aloft with the tankage we have available, and even when you throttle back your fuel burn doesn't drop by much. Look up the Foland Gnat crash in Bossier City, LA in 1991 - he only had 90 minutes total fuel capacity. One missed ILS approach, and he didn't have the fuel to make a second. Double fatal. Another is low accelleration. Thrust from a turbojet is not 1:1 comparable to a prop, it's a more complex relationship than that. But you won't be leaping into the air. Count on long runways. Not even remotely. If you honestly, really think that - rethink building an airplane. You don't have the basic understanding needed to build and fly safely.

You might check the Cozy list search feature http://www.maddyhome.com/cozysrch/search and search the word "mach". Just so you know, I'm NOT a fan of jet engines on these airplanes.

Berkut DOES have them - they are just very small. They dam up spanwise flow at low speeds and reduce roll coupling. Without them, low speed handling suffers significantly. TE fences - like Klaus' - help a lot.

No, there aren't. They weren't valuable enough to spend time and money (and risk pilot's lives) to try to develop a fix. The problem is inherent in the control system. You could try changing it to a conventional tail, but that would be building a whole new plane.

The layup for the Berkut gear was COMPLETELY different, and shouldn't be included as part of this calculation. A totally different shape and material. The lighter weight legs for a lighter airplane makes sense. That would also imply that standard Velo legs might be reasonable for a Cozy 4

I agree with the first part, Steve said he worked with the Swings developing the Velo gear and his LE gear was based on it. But he had his own molds and made his own legs. That leads me to thing that they must have been slightly different. Maybe they're a little smaller overall, maybe some of the dimensions are a little longer or shorter. But if they were the same - or close enough to be adaptable - my guess is Steve would have used Velo legs and adapted. We'll find out for sure soon enough.

Steve made his own. I can't imagine he would do that if he didn't need to.

The aft weight is also a good excuse to install one of the electric nose lifts, like Jack Wilhelmsen's.

My experience has been with 180 HP parallel fuel injected 360's. They do exist, carburated ones can be converted with an either a Bendex or Airflow Performance servo. However, to my knowledge, all 200 hp angle valve 360's are injected. I don't know of any Longs flying with the 200 hp enigine, but there are plenty of Cozy 4's that are. They ARE heavier, and even the 180 hp version is difficult to ballance on an EZ.

There's the Waspair Tomcat - but I'm only posting this as a warning. The Tomcat is an extremely dangerous aircraft. There are a few around and occasionally show up for sale - DON'T. It can and often does get into a spiral and doesn't have the control authority to get out. The Pterdactyl is a pretty nice little airplane, Dave Froble (who builds them now) is a good guy. http://www.geocities.com/pterodactylclub/

Here's an analysis of the Berkut gear. http://www.atnet.it/lista/Aircraft/milwauk.htm The legs started out all carbon. There were failures (creep) at the bottom, so we went to aluminum bottoms. Then failures (delams) at the bend, so we went to aluminum top ends. I don't know the overall weight, including the hydraulic pump and fluid. It's well under 100 lbs. Especially if you're looking at the increase over the standard gear. We did a test for PFA certification in England, hitting at 800 fpm with a video camera in the gear bay. 8 landings, no damage. We looked at going to all aluminum, it would have been much more expensive and heavier.

It would be a supurb engine for an EZ. The problem is that it isn't available yet - and it may never be. It's been just around the corner for years.

I agree. Tiger Tim still thinks the 320 is faster. Of course, he probably also thinks Jimmy Carter was a great President. Those are terrific speeds, the best I got out of mine was 206 KTAS (also uE calced) but that was in primer and with a tired, stock engine. I think there are 2 big drag points to go after now - cooling, and winglet intersection. I'm not going to address either in this rebuild (of the 540 Berkut) I'm just modifying things that I consider to be safety issues. You're exactly right about the air filter, a LOT of EZs are flying with filters that are too small, per K&N's recommendation. I'm trying to build one right now that has a small round filter inside a large oval filter, to increase the total square inches, because I'm using the largest oval I can fit. I can't quite visualize what you're proposing for the oil cooler in a downdraft cooling setup.

What's your WOT level low altitude speed? (I'm assuming the 222 KIAS was with some downhill smash)

Berkut wings were 2 lb foam, but carbon skins (4.7 oz/yd uni) and three plies on both top and bottom - +30, -30 and spanwise. Also carbon fiber sparcaps and the shear web was increased from 6 plies to 8. And the solid core foam wings were vacuum bagged at about 12-15" of mercury. The 1' fuselage stretch, a long nose (battery in front of the nose bulkhead) electric nose gear, and a short as possible engine mount made the CG come out about right.

As far as I'm concerned, the best engine for a LEZ is a 180 hp injected 360. Mike Melvill and Dick Rutan agree.

You also might look up the "C-wing" configuration by Kroo. It would unload the canard in cruise. It would be a radical change for an EZ that should only be done with the intense involvement of highly trained people and a lot of testing, but it's something I've thought about.

You mean, other than changing all the flying surfaces and sparcaps to carbon, vacuum bagging everything, using higher density core and a completely different engine mount and mounting system? Nothing. There's a 540 retract Cozy flying, and a supercharged 540 E racer. The identified weak points right now are 1) Rudder flutter (add a Gurney flap to get some more in force at high speed and it's fine) 2) Canopy thickness (I wouldn't want to hit a duck at 240 kts) and 3) running out of nose down trim at high speed.

Don't know. The decision to curve the upper strake was part aesthetic, part rule of thumb, part wild guess. Basically Dave figured that since it was out in the wind it should be lifting, so he cambered it. Of course, a flat surface with a round nose and a pointy tail will generate lift too, but the camber looked good, and it might have the effect of moving the CL aft. Since he'd just lost his Long EZ in an aft CG deep stall, moving CL aft seemed like a good thing.

There's also at least one unauthorized copy of a Drybread gear out there somewhere. It came up for sale a few years ago, I asked Steve about it, he swore and said it had come about when someone had laid up some legs for him and laid up a few extra that they sold on the side.

Anyone have an idea on the weight of the V10? I've got an application (non aviation, but weight sensitive) that it might be good for.

A few weeks ago I was in Washington DC, played hooky Friday afternoon and went to the Smithsonian Air and Space museum on the mall. They have a NICE Wright Bros. exhibit now, in it's own room. They have one of the 3 or 5 surviving Wright Bros. bicycles. It looks just like a standard, ordinary bicycle you'd see at the beach. One speed, of course, and the handle bars are a little odd shaped, but the frame geometry is utterly conventional. It's 110 years old. If I go to my local gun shop, and buy a pistol, there will be revolvers and automatics. They look basically the same as they did 100 years ago. No big surprise, I have a Colt 1911 issued in WW1, it's absolutely functional. If I were to buy a shotgun or rifle, odds are I'd buy one that works the same as something John Browning designed in the late 1800's. Build a motorcycle that doesn't work basically the same as a 1918 Indian. Some things can stagnate for decades, then make a leap - like lights. For years there was the incandescent bulb, copying Edison, and florescent, copying Tesla. Now we have metal halide and LED. There are some very different airplanes out there that have a chance to really change things - the Facetmobile and the Carter Copter come to mind. But things are convention for a reason - they've risen to the top, and they're hard to beat.

Two thoughts... First, there weren't many used homebuilts available then. Now, if you want (say) a Glassair, you can buy one with 250 hours on it for less then you can build it. If you're trying to sell kits now you're in a market that's basically saturated with pre-existing product. And since people don't fly much (50-100 hrs per year, max) they can last for decades. Second, there's a HUGE amount of innovation. Mostly, at Vans, with CNC pre-punched skins and machined parts. CNC and the change from hard tooling to software is totally changing the way we make these things. The NEXT cycle will be how they end up looking.