What makes the berkut VNE higher than a long ez?

[ColinB]

so what does the berkut have over the long/open ez other than a big engine?

 

i know they use carbon fiber ect but what actually contributes to the higher VNE?

 

is the long just as safe at these higher vnes if you have the power to get there?

[Jon Matcho]

What makes the berkut VNE higher than a long ez?

 

Money.

 

Ok, seriously, it's money. Ok, I promise, I'll stop (sorry, it's Friday and I'm feeling 'done').

 

Although the Berkut looks like a Long-EZ, it's designed and built differently. As you pointed out, it uses carbon fiber in several areas, and with different layup schedules than what the Long-/Open-EZ plans call for. After all, it was a kit, with its parts produced from molds (I'm sure some were not) -- altogether very different than a Long-EZ.

 

At the end of the day, the designer felt the Vne was greater than that of the Long-EZ and advertised those numbers. I presume it was tested accordingly, and do know it was very fast in a few races.

 

i know they use carbon fiber ect but what actually contributes to the higher VNE?

Strength (and weight?) of the airframe, combined with a big a$$ engine.

 

is the long just as safe at these higher vnes if you have the power to get there?

I'd bet "not quite". The Long-EZ was NOT designed to have a 540 in the back, whereas this was in mind as part of the design effort for the Berkut.

 

If I had unlimited cash, I'd probably consider an Open-EZ 540, or at least a 360 (or 390 or 400). Not in that position, I'm more intrigued by a high-power 320 with adjustable prop.

[dpaton]

The Long-EZ was NOT designed to have a 540 in the back, whereas this was in mind as part of the design effort for the Berkut.

I'm not an AeroE, but I do have a signifanct MechE background (behind my EE degree) and I'd be very wary about expanding the Vne of the Long or OpenEZ without some very stringent flight test requirements. There have been anecdotal reports over the years of some very high speed durability for the structure, but there has also been a disturbing report of a fatal crash caused by total structural failure due to catestrophic flutter, induced in a high speed dive.

 

is the long just as safe at these higher vnes if you have the power to get there?

The similarity of the design of the Berkut to the Long starts and ends with the idea of it being a 2 place tandem canard. The airfoils are different, the fuse is different, the control surfaces are different, the wings are different, the canard is different, the construction method is RADICALLY different. All of that adds up to a completely different airframe. Comparing it to a Long is like comparing oranges to beachballs. Yes, they're both round, but that's about it.

 

If you really want to, sure, put a turbo 320 in the back of a Long, keep it cool, and slowly expand your Vne envelope, but be aware that the airfoils are not designed to work well up there, they get inefficient at high speeds. Beware of mach tuck on the canard. Watch out for flutter. Wear a parachute and know how to bail out. Be safe. Taking a plane beyond it's design limits, however artifically safe they may have been made by the designer, is a highly dangerous proposition and must be approached with the same care as any potentially fatal endeavour.

 

I'm not saying it's bad to go fast, just make sure it's done carefully.

[ColinB]

well my point being weight wise and engine wise the sensible thing for me is a small jet

im a prop tech in the airforce and my trade is turbines

 

so a small jet makes a lot of sense to me ie gnome/T58

its been done before and its not a difficult task either

 

the main question is what does the airframe need to make it to berkut speed?

[dpaton]

the main question is what does the airframe need to make it to berkut speed?

In short, it needs to be a Berkut. Different wing and canard construction (pulled from a mold, vacuum formed, oven cured), materials (carbon fiber), and airfoils (whatever Dave Ronneburg used) would be a good way to start.

 

-dave

[rpellicciotti]

well my point being weight wise and engine wise the sensible thing for me is a small jet

im a prop tech in the airforce and my trade is turbines

 

so a small jet makes a lot of sense to me ie gnome/T58

its been done before and its not a difficult task either

 

the main question is what does the airframe need to make it to berkut speed?

I know the jets they are building at EZ Jet, Inc. have been professionally engineered for 2200 lbs gross weight and 275KIAS. The main spar, wing spar and canard layup schedules are all different from the Long-EZ.

 

For what its worth, I have had my EZrg up to 200KIAS, doing "stick raps" at each 5 knot interval. No problems indicated. My aircraft is not a good comparison though. It has retract mains, carbon fiber ailerons, no lower winglets and a canard that is 20 inches shorter than stock.

[Waiter]

Although the aircraft may have been designed with the higher Vne in mind, I would NEVER placard any aircraft for a "design" Vne unless it has been flight tested.

 

I test fly the aircraft to a speed of 10% over the recommended Vne. As mentioned by rpellicciotti, I do this in 5 knot increments starting at about 130KIAS.

 

When each test speed is reached, sudden control inputs (jabs) are input to see if "flutter" can be introduced. Each test speed is completed with a sustained 2 G turn in both directions while holding the test speed.

 

My LongEZ is placarded for 230KIAS Vne, I have personally tested it to 260KIAS.

 

Flight testing any aircraft can be FUN, and is a great tool for the pilot to build up confidence in the design AND the manufacture of the aircraft.

 

The flight test program must be well thought out and have a written plan. No plan, no flight test.

 

I've discovered that it takes me just about 40 hours to perform a complete test program on most home built aircraft of medium complexity.

 

The FAA publishes an Advisary Circular on flight testing, there are also numerous books on performing flight testing (home builts). I believe most competitent GA pilots are capable of performing a complete test program.

 

And of course, ALWAYS wear a parachute when performing this particular test sequence.

 

Waiter

[ColinB]

thanks for the replys

 

ill deffo be testing it in detail

 

im just trying to find out if and what other people have done to increase the vne of there aircraft so i can look at what i may need to do to mine

[ColinB]

having been doing some reading up on the berkut

 

so far what i belive to be true is

 

the berkut isnt really much different from the ez airfoil wise

the shape of the berkut was modded to house the larger engine

and the nose and canard moved forward to counterbalance the weight of engine

the fuselage is premoulded mainly for speed of build and to keep it a kit plane

 

so if i were to utilize a jet engine that is really not a lot different in size and weight to a piston engine of the normal ez's then the weight int really an issue in regards to balance and the ez wont need huge mods for the size either

 

and if the cabon fiber was utilised in the same areas as on the berkut (hopefully the world shortage will be over soon) then with infinity retracts the ez should be quite capable of high speeds

 

what i do find interesting is the larger aileron that increases the roll rate that would certainly add to the "fighter jet" feeling

 

 

so could imitating the berkut in this way be the right direction to take?

or have i missed somthing very fundamental

 

end of the day we are in the experimental catagory

[Jon Matcho]

My $0.02 worth of feedback follows...

 

the berkut isnt really much different from the ez airfoil wise

For your intent and purpose, true -- any differences are negligible.

 

the shape of the berkut was modded to house the larger engine

and the nose and canard moved forward to counterbalance the weight of engine

Sounds right, although I don't know much about the shape mod -- maybe a more rounded body to support the 360/540 option. However, I know a 360 will fit a stock Long-EZ and not look much different, if at all, from a 320 EZ.

 

the fuselage is premoulded mainly for speed of build and to keep it a kit plane

Kit parts also move the possibility of builder error out of the customers hands and into the manufacturer. I don't know the layup schedules, so the fuselage -- and many other molded parts for that matter -- may be stronger.

 

so if i were to utilize a jet engine that is really not a lot different in size and weight to a piston engine of the normal ez's then the weight int really an issue in regards to balance and the ez wont need huge mods for the size either

Except your jet engine will produce more thrust

 

and if the cabon fiber was utilised in the same areas as on the berkut (hopefully the world shortage will be over soon) then with infinity retracts the ez should be quite capable of high speeds

Why not try and find an unfinished Berkut project? They're out there.

 

what i do find interesting is the larger aileron that increases the roll rate that would certainly add to the "fighter jet" feeling

Supposedly.

 

so could imitating the berkut in this way be the right direction to take?

I think if you want to go fast, the Long-EZ design (tandem) is the best way to go.

 

or have i missed somthing very fundamental

Nothing more than the magnitude of how big this project is. You are encouraged to experiment -- we all do -- but not to strap a jet engine on your back, hold out your arms, and launch.

 

end of the day we are in the experimental catagory

Best case: You make a beautiful aircraft and it's the talk of the scene for a while. Worst case: You die. Typical case: You spend a lot of time and money chasing a vision before realizing this should really have been your 2nd plane building project. The great thing is that you're thinking about building something, and even the most basic EZ is an exciting aircraft -- at least to us here.

 

Did I mention this was my $0.02 worth?

[rpellicciotti]

There's a lot to be said for that "2nd project". Let's face it, a lot more airplane projects get started than are ever finished. The amateur-built airplane exists solely because it was sold to the FAA as "educational". No one who has every actully built an airplane would argue with this. You learn a lot by doing it.

 

When I embarked on my airplane building education (back in 1983), I had stars in my eyes. I had my mind set on a scaled down, WWII fighter. This airplane posed all sorts of challenges:

• Size and parts count of a Bonanza
• complex systems such as hydraulic flaps and landing gear
• liquid cooled engine with radiators, plumbing, etc.

Add to that, everyone in my family telling me that I couldn't build an airplane and actually fly it.

 

Truth is, if I had actually started that ambitious project, I probably would not have finished it. Cooler heads prevailed and I started with a much simpler airplane, the RANS S-9 Chaos. This airplane came in a complete kit, was a simple tube-and-fabric airplane with fixed gear and no flaps. Building it, I gained a tremendous amount of experience and demonstrated to myself and others that I could do it. In fact, I enjoyed building that airplane so much that I went on to build 4 more RANS airplanes of different models. With each one, I learned more and I had a great time.

 

Now that I had proven that I could build a simple airplane, it was time to move on to something more complex. I discovered the E-Racer about this time and it had everything I needed: Auto engine power, composites, retractable gear. This would be the next step and complete my education so that I could build my fighter. I ordered the E-Racer plans and got started. I had the good fortune to get to know Shirl Dickey and he taught me a lot. I even had a small hand in a Nissan TV commercial that featured the E-Racer. I had also met Robert and Valerie Harris at The EZ Hangar (now EZ Jet). They were great to me and taught me a lot as well. RealLife kicked in and several job layoffs and other things caused me to have to sell my incomplete E-Racer. I have fooled around with several different airplanes since and I am enjoying my Long-EZ very much. I still have not started that fighter but I have been working on a P-40 replica that a friend is building. I have also had the chance to work on and fly some actual warbirds (T-6, Stearman, Sea Fury) so I am content to have my high performance EZ and the fighter may never get built.

 

My point to this long story is that few of us are prepared to build a complex airplane with mods that no one has ever done, as our first airplane. Building something simple, with support from the manufacturer or a great community like this one should be the first step. Most of the highly modified airplanes out there are 2nd or 3rd projects.

[rpellicciotti]

 

Why not try and find an unfinished Berkut project? They're out there.

 

 

There's one right here on this forum:

 

http://www.canardzone.com/forum/showthread.php?t=1856