8/6/2008

The Sled Flies !!

Not only does it fly, it fly's great! Yea, I know it looks pretty rough in the below shots, but keep in mind, this is a prototype. I don’t care what the outside looks like, as this is a mule to test the design. I put some red tape on it in places to help see it as well. I also taped shut, one of the full flying rudders so that in case I had rudder flutter, only one would tear off the plane, and I’d be left with one keeping the plane stable in yaw.

Things learned:
* Very under powered with prop engines. I had unacceptable climb rates. However, I did learn that it’s very stable and easy to fly at slow speeds. I bet max speed never exceeded 75 mph.
* Balance was spot on. I mean right on the nose. I was stunned, as this was an area of some uncertainty.
* Aileron trim was spot on as well. Not even one click of aileron trim.....
* I shifted back the main landing gear points during former design from where I wanted them to go (close to balance), to a position that could fit the retracts with more margin in the space needed. This also shifted them back to a more scale location. I was concerned that it would make it difficult to rotate with now more weight on the nose wheels, with the design change. It turns out my concerns were unfounded, and the nose lifted easily, with just one third up elevator on the takeoff roll.
* Control throws seemed ‘just right’ for my tastes. They were responsive, yet smooth.

Things I had planned to test on props, but can’t due to inadequate power:
* Stall testing. It would have taken 15 minutes to climb to altitude to do stall testing. Considering I would have run out of gas at 10 minutes, not going to happen on props.
* Flutter testing. I had wanted to take it to a very high altitude and dive it under full power to see if I had any flutter issues. As I just said above, can’t do it with the power available.

Overall, 75% of what I wanted to test on props was accomplished on the one and only flight, that it will ever have on props. I’ll have to continue testing with turbines, but will have to be more cautious than I would have been able to be on props. So, the next phase is conversion to turbine power, but leaving the crappy looking fixed gear on it for now.

Current weight it flew at was 51 lb.. Total thrust output from props was 26 lb.. Thrust from turbines should be 50 lb.., which will completely address the under powered issue. Weight of the plane should be about the same on turbines, considering I’ll pull out the second radio system, water transfer system, and the weight drop mechanisms. Also the fixed gear are very heavy, as the mains are ¼ by 2 inch aluminum strap. Overall weight / balance / thrust issues are all on track.

Over all, considering the first test flight was up and back down, without so much as a scratch on it, I’d call it a great success so far...

First take off. Although it’s got a nice nose high looking climb, it’s actual rate of climb was very slow. Looking at the photos after the flight, I realized that it’s very stable with a very high angle of attack....good stuff..

Half way through the first turn, I told Jerry, that the balance was spot on, but I was concerned about clearing a tree in the distance. I told him to drop BOTH weights we had onboard, in case balance was way off. After doing so, 2 lb. was ditched from the plane. The tree was avoided, but by how much I don’t know. It passed in front of it, and I would not have been surprised had it landed in the top of it; it was that close. Just below the plane in this shot you can see one of the weights falling from the plane.

Flyby at about 100 feet. The gear sticking out and props on it just seem wrong, but I was still pretty excited about watching it fly by after 6.5 years on the project.

Absolutely perfect landing. Literally, mains straddling the centerline, with the nose still 6 inches in the air. It was a real pussy cat to fly. It needed at least another 20-30 mph for it to feel solid, so I’m really looking forward to the turbine conversion, and getting it up on step.

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