Ok guys, here is the complete chronicle of my experiences with my new L-39:
I test flew the jet back in April and only logged one flight. The plane flew well but I was unable to retract the gear. I had lost air due to some airlines rupturing from heat. During that flight the L-39 felt solid and was very aerobatic. The landing was smooth but I was shocked that when I taxied back to the pit I saw that the wings were completely destroyed. The force of the landing caused the wing skins to delaminate from the ribs and even the trailing edge spars split. I immediately contacted Wagner of Rcjetmodels and he had me cut sections of the wing apart to use as color samples for the new wings that he promised to send. Wagner and I discussed the design and materials used for the construction of the L-39 wings and also what improvements should be made. Wagner took the color samples and my notes to China during his factory visit. In about 45 days the wings had been totally redesigned with new materials and construction techniques. When I received the new wings I was immediately drawn to how solid they felt. They were very strong. Absolutely no flex at all when I tried to twist and tork on them. I also noted the extensive use of Carbon fiber, different higher quality epoxy and a new material Nomex that was used in place of the balsa parts (wing skins / spars). The color match of the new wings was perfect!! After assembling the new wings I was anxious to fly the L-39 again. I made arrangement to meet Wagner in Titusville, PA for test flying.

Well it was a hectic two days of test flying.
On the first flight I did not retract the gear for fear of the heat problem. My new heat shields for the elevator servos worked great and were better than my original setup. Still after landing I found that I had burst my airlines again. We spent all day repairing airlines and flew all but one flight with the gear down. I rerouted the lines in front of the first engine bulkhead but still was getting heat damage. I ultimately enlisted the help of my friend Rich Miller who was kind enough to bring an assortment of heat shielding materials to the field. He first replaced my airlines with HD lines from DreamWorks. next the lines were installed into a woven tube that is used to insulate lines and such. The tubes were than wrapped with aluminum tape. End of failures in that area. We believe that the excess heat is caused by the far too small pipe supplied with the kit. The rear ID is only 2.5". My P-70 posted good numbers as far as max and average temperature were concerned. I verified these numbers with Jetcat. Wagner Is going to contact the factory about building a larger pipe.

Now the flying.
This jet is a dream to fly. It is super smooth and will gracefully perform all aerobatic maneuvers. We did it all. Point rolls, slow rolls, loops, inverted, knife edge and so on. With the gear down the plane cruises at about 130 or so. But hold on cause when the gear is retracted this thing transform into a sport jet!! It is very very fast. You wont believe it. An awesome plane to fly. Takeoff are so pretty to watch. The ground handling is rock solid….tracks like a cat.

There were problems. This is a great airplane to fly as long as you don’t land it!!!!!
We flew the jet a total of 8 flights and the first 5 landings should have completely destroyed this plane. The jet would just fall out of the sky. I mean you are on final, everything looking good, great airspeed and without warning the jet just falls out of the sky. Absolutely punishing the landing gear and wings. I’m talking dropping in from like 3 feet! Every type of approach was tried, fast, slower, steep, flat, full flap, take off flap etc and this thing kept falling out of the sky. The jet also had a tendency to balloon on final as it approached the runway. This too resulted in the jet now sitting 6 feet in the air with no airspeed……..down to the runway she goes.
I can’t tell you what a beating those retracts, struts and wing took. The great news is that new wing design is awesome. There is zero sign of any damage or fractures anywhere(I gutted them after day one of flying and examined the inside with light). The landing gear and struts are perfect as well. Remember the spring setup I choose in my building thread. well it works. There is actually no damage anywhere on this jet despite all this.

So that was the end of day one. After spending all night taking the jet apart and looking for damage I then had to figure out what was wrong and a strategy for the next days flying. The CG was rechecked with empty tanks, full tanks and ½ tanks and was determined to be fine as per my original setup. The next day we logged three more flights with absolutely perfect grease job landings. So what was the problem? Well when I landed with take off flap (15 mm) the jet would balloon on final. With landing flap (40 mm) the jet would fall out of the sky. What I did was reduce the landing flap to 25mm. My thought was that is was a good number between the others and should give the perfect ratio between lift and drag. I also reduced my elevator throw from 20mm to 15mm. As a note, I don’t use expo. These settings along with flying a specific approach resulted in a stable, predictable approach that allowed the jet to softly return to the runway. My approach was a constant descending, slightly nose down approach. You must keep the nose slightly down, pointing at the runway till you are about three feet off the ground. Then gently level the jet to bleed excess speed and finally pull the nose up slightly and hold it. The jet will gently land on the mains followed by the nose. Do not try a high alpha power on approach. this is a conventional wing jet and that technique does not work.

I can’t tell you what a great flying jet this is. And now a great landing one too. Those landings are now so pretty. As I get more time on the jet I will update the thread. I will bring this jet to the D.O.G.S. rally along with my Panther so you will get to see it first hand. It was a long journey but now I have it all sorted out and will no doubt end up having this be one of my favorite jets!!

I want to thank Wagner of Rcjetmodels and FeiBao for the outstanding customer service as we worked out the kinks on this project.