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Home - Construction Photos - Contact Test Flight is Successful!
The Prototype has completed 2 successful flights. The first flight was to prove controllability and gather slow speed/stall data. Overall the flights went extremely well! The morning started with some taxi tests. Low and high speed. With a slight amount of up elevator applied the nose remains light and is solid. The reverse caster in the design of the model is negatively unstable but seems to handle well with low control throws from the steering servo. Obviously the full scale Cheetah has a positive caster design which works flawlessly. There was no way to really acheive this in the model so we had to improvise and make the entire nose gear steerable. The system works as designed.
After taxi tests we were ready for the first flight. The OS 1.20 four cycle engine was tuned and swings the 15x8 prop at about 9000 RPM. Plenty of power for the 14lb model. I lined up the Cheetah on the centerline and fed in full throttle slowly. Considerable right rudder was needed to keep a straight track. Lots of torque coming from the OS 1.20.
Within about 75' I applied a bit more back stick. The nose gear came off the ground and a second later the mains were up. She was flying. Pitched up into climb attitude and let her go. No aileron trim required and 2 clicks of down trim had her flying straight as an arrow. I was amazed at how straight she tracked right off the building board. After a few circuits at altitude and cruise speed it was time to slow her down and get a feel for flaps up slow flight. Slow flight is very docile. No bad habits. Pulled power back to idle and held altitude to induce a stall. Stall takes a while to happen. There is considerable "mush" before the break. The break is abrupt but easily comes back under control.
The first landing was done with about 10° of flaps. I came in hot not knowing what the true landing approach speed should be. Better to come in hot and use up more runway than stall on short final. Touch down was smooth and a non-event.
Second flight went even better. Take-off was done with about 7° of flaps. The flaps seemed to decrease the roll by a noticeable amount. Once in the air on the second flight I decided to do a non-scale aileron roll. The cheetah loved it. With full aileron deflection the roll happened in about 1.5 seconds. Very axial and by entering in a slight climb there was no altitude loss.
Final landing was much slower and hence much shorter. I used 30° of flaps. At about 2' I began the flare and held it off. It slows nicely and under full control all the way to touch down. The next flights will consist of more flap experimentation along with slips. I'll also play around with some things we can do with the model what the real one can't.... spoilers. By flipping up the ailerons together about 10° you can get a spoiler effect. I suspect that with full flaps 40° and spoilers, I'll be able to get this plane down in a fairly short distance and over an obstacle. More info coming as test flights continue!
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