i3dm

My Feedback: (51)

Hello guys,

a friend of mine built this Lavi:

http://jdenterprise.net/IAI/IAI.htm

and here is what happend in his test flight:
http://www.liorzahavi.com/videos/pal...vi%20crash.wmv

fortunately the plane is repairable and will be ready soon.

We would like to know a few things:
1. anyone has any expirience with this plane ? CG \ control throws ? canard incidence ?
2. any ideas what might have happend ? the builder says he thinks he had a lot of canard control (possibly way too much). i didnt witness the plane myself.

Any tips about this plane would be more than welcome, before the next flight attempt !
thanks guys.

rhklenke

My Feedback: (24)

That was not a stall, it was clearly a commanded extreme nose pitch down. Either he had way too much canadr throw as he stated, or some linkage broke, or a servo went hard over, etc.

I would think that for normal flight, the aft edge of the canard should move maybe 10mm up and down - no more, probably less - until you get it up and away and can test its effectiveness at altitude...

Bob

ravill

My Feedback: (11)

What Bob said. Poor Wojteck lost his beautiful BVM Rafale to too much canard incidence. Todd at dreamworks has flown no less than one million eurofighters (say that with your best Dr. Evil voice! ) and the incidence on the canards seem like almost an after thought. (I believe they are like 5mm up 8mm down or something like that...)

Raf

meps

My Feedback: (10)

It appears to me that with his transmitter sticks in the neutral position, he may have had some down already dialed into the canard.

jetjohn

The same applies to the Rafale, it took me two flights to get a good blend between the incidence on the Canard and a match to the Elevons.
Now it flys beautifully.
I use lots of canard movement with gear down to aid take off's & landing's but small amounts for flying using the retract switch to put movement on & off.

That video looked like there was a lot of down mixed in to start or a major component failure.
Arn't the canards on the Lavi fixed?

All the best, and better luck next flight,
John C

Shaun Evans

Wow,

Sorry about your troubles, but I gotta say: It's amazing that the plane didn't blow up after hitting the ground like that. I watched it again and again and didn't see any debris scatter about or anything. Tough bird, apparently...

3DHELINUT

My Feedback: (3)

Raf you are 100% incorrect on what happened to Wojtek's Rafale, Wojtek had an issue with the elevon linkage that was binding and causing aileron interation with elevator command.

I am currently using 50mm of canard travel on my Rafale and it flies perfectly, takeoff and landings are smoother with this amount of canard travel and in flight i can hardly tell the difference with or without the canards.


Alan

erazz

You have to separate 2 different terms. THROW and INCIDENCE.

Throw is how much the surface moves up or down. Incidence is the angle of the surface to the surrounding flow.

For a first flight of a canard model which has elevons I'd set the throw to zero. You can increase them later on and get the right values. Meanwhile you need to set the elevons right.

The incidence for the canard should be positive. When you look at the video they seem to be at a negative incidence. This coupled with a very probable aft C.G. would cause exactly what we saw: a very unstable airplane. I'd say fix the canard with a positive incidence of 1-2 degrees and move the C.G. 5 cm forward and try again.

BTW. The original Lavi did not have the canards functioning as flight controls. They had 3 positions. Takeoff/landing was set at a positive incidence. Cruise was set at zero or a slight positive angle. Maneuvering was set at a negative angle. This was done in order to achieve different stability modes with the airplane becoming less stable as the angle lessened.

i3dm

My Feedback: (51)

erazz, thats for the clarification about the terms, all known already though.
my friend swears he has the CG slightly IN FRONT of the recommended point by the manufacturer, thats why im asking if others had expirirnce with this kit (since it does look like an aft CG case!).

DennisF

Hello
I had been sent the video of the Lavi and replied to it what I don't se mentioned and excuse if I am wrong is that the owner of the model changed the wing design making it longer and wider obviously this changed the CG location for that wing I gave him several thing's to look at and also agree with other's that it looks like a down command was given for some reason as the plane took to the air OK with a turbine for power there could be interference causing a radio problem hard know what happened from here as I offer the plane I recommend the canards be in a fixed position for the first flight's I have had customer's dial in all kinds of mixing and then wonder why they got into trouble good to hear that the plane is repairable.

Rg's
Dennis Fuente
JDE

JetflyerJ

My Feedback: (67)

That's what it looks like to me as well..

lavi rider

My Feedback: (6)

From looking at the video and speaking to the pilot a few things are clearly evident!!!

A. canard incidence is negative relatively to the wing... can be seen as the plane is in front of the camera.
B. pilot has to pull hard to unstick but when realize that his climb is too steep he reduces the pressure on the stick and immediately the plane went down.(spoke to the pilot)
C. throw on the canards was to high ~30mm up and down.

lavi rider

My Feedback: (6)

by the way an aft C of G will not point your nose down aft stall

drorso

Hi,

I found this post while looking for info on the Lavi. I'm considering buying a J-10 (FEJ) and paint it like the Lavi.
I see here and and in another old post that there was a kit provided by JD Enterprise, however couldn't find this manufacturer online.

So, can anyone provide more info? are there any kits still available?

i3dm

My Feedback: (51)

Hi Dror.
i dont think JD enterprise exists anymore.

CARS II

My Feedback: (7)

He is right, Dennis stopped any work or sales related with his bussines like 4 or 5 years ago.