I crashed my RV-4 kit on it's third flight, "my" first flight on this kit during a take-off. I had a very experienced 30+ year instructor take it up on its maiden +1 with some difficulties. He had me make some adjustments for the sensativity (expo). Anyway, it was proven to be airworthy so I can't say anything bad about this kit. My take? It was human error that caused the crash. Anyway, the damage seemed pretty bad at first. The wing cracked in half at the root so it was a g-loaded crash with the firewall also seperating. No damage to the fuselage. After doing initial repairs and looking at the plans, I have been able to re-attach the wing halfs successfully and am working on the NEW firewall. The plane should be complete in about a week. My question is, does the RV-4 need a significant amount of speed on take off? It appears I went into a tip stall (to the left) which probably would have been recoverable if I where more experienced. I feel I had a good takeoff run and the plane lifted itself up into the air, then things got bad. During the stall, the nose pitched up (probably due to my input) and to the left. I had applied full power and was just starting to recover until I ran out of sky. Perhaps some right rudder would have helped? The aircraft impacted soft grass level on the gear. The kit has installed flaps but I did not use them on this flight. Anybody have any general recommendations or info on this plane perhaps any experiences with flight characteristics? I'm having our clubs experienced pilot take her up again but was wondering if you all had any aditional good advice.

Thanks,

Yes, relative to trainers or other flat bottom airfoils with light wing loading. About 1/4 of it's maximum speed BEFORE you can begin to lift the front wheels. That is one flaw of sport models. They teach you that raw horsepower beats gravity. In a RV-4 (I've never flown a model of one but it is a "conventional" design) you have to get the wing flying before you can rotate off the ground. Like with most "real" prop aircraft: if you try to lift off before the wings are generating enough lift you will stall. Same with a turn too soon. One wing loses lift as you bank, not enough total lift to keep the plane up, crash.

You don't mention the size or version of your model, so my answer is generic.

The real one stalls at 54 mph and needs 475ft of runway with two people. That's actually pretty forgiving. Models are usually better performing than their full size designs.

[link=http://www.vansaircraft.com/public/rv-4int.htm]RV-4 (the real one) Specs & performance[/link]

If you are taking off from grass that adds drag, also.

Going from 30 mph to zero instantly is about a gozillion "g"s. All crashes are loads and loads of "g"s. It's not a lineal relationship, but a 5mph car crash into an immovable barrier (like the earth) puts a 5"g" load on your neck for a fraction of a second, enough to snap vertebrae. Depends on weight and speed.

We had two of those kits at my club. There is a lot of frontal area with that cowl. Keep it full throttle on takeoff and rotation. You didn't say what engine you have. One guy had an OS .40LA and it barely got the plane in the air. I remember that it landed hot and fast. It would be good to learn how it stalls when you are up high enough.

Wow, thats kind of a downer as I'm just finishing up my GP RV-4. I've got a heavy RVC 58 on it, and the beast is going to need a bit of weight in the tail to make the CG line up with the plans (about 6.5 pounds wet). I've been spending most of my flying time with an Adrian Page supercub (after I crashed the GP taylorcraft on takeoff one day...bad day...just a bad day), the supercub flies great, lots of rudder required, very much a good warm up plane no matter what you are flying.

I only have about 80 feet of runway available to me, should I be finding a better takeoff line for my plane? How much runway did you use up before the liftoff? Should I be using my flaps and not be scared of the fifth channel?

eniac

I have a GP RV-4 with flaps added. I have to say I have never thought that the wing loading was high. It actually slows down quite nicely for landing, especially with the flaps. I have found that with too much elevator at a slow speed it will snap. I would class the RV-4 as a pretty docile sport plane. For those wondering YES ADD THE FLAPS.

I have one and have flown it for two years. Powered by a Magnum .46. HyTec radio with the flaps. It slows to a crawl with the flaps and without them it is a touch fast, but still flys great. One funny thing it does is at higher speeds it will wag its tail just a bit. Nice solid plane though. I feel it is for someone with a few planes under their belt and comfortable with low wing flying.
JEB

Well my RV-4 repairs are going very well. I have already repaired the wing halves and inserted a small plastic bracket with screws for additional reinforcement. I also used small screws to add the new firewall as well as epoxy. It is drying as I type this (I considered fiberglass or composite fibre but I'm still learning about it). All I have left to do next are some final inspections, then check the weight and balance plus rechecking symmetry and of course servo and electrical. I reused my plans to recreate some parts so as a newbie kit builder - I'm glad I kept my plans handy. As for my engine, I have the OS .46 AX and it appears to be doing a good job. I think she should be airworthy in about another day or two. One thing I have to say about the RV-4 is she's a tough bird and didn't take on too much damage. As for folks building her right now, don't worry about the kit. It's a good kit -- the reason I crashed was due to pilot error [] Anyway, thanks everyone for the advice. I do have the flaps installed but haven't played with them much. I'll let you all know how she does in the air after her repairs. I'm not flying her myself but a more experienced club member is. Thanks for the replies.

Below is a picture of my RV-4 before the crash. She looks the same after repairs.

cheers

Just to be on the safe side, check CG, again.