Yesterday, was an extremely exciting day! We did not end up making an attempt at the AHS Sikorsky Prize, but we were definitely getting close enough to taste it! In out trim flights leading up to the attempt we managed a steady 5 foot climb and a flight that lasted about 30 seconds. You can watch our best flight here. When we tried a higher powered climb, the rotors were quickly thrown out of balance and the flight was blown down. Our best guess is that higher forces on the drive lines are deflecting the structure and causing crucial bracing lines to go slack. With the lines slack we lose our torsional stiffness and it’s easy to have a ground/line strike with one of the blades. We’ll be addressing the issue and back for a second attempt in a couple of weeks time. Continue reading below for a full summary.
First a big congratulations to Trefor, who acted as the trim pilot for the first 6 flights, and became the 3rd AeroVelo team member to take flight! Great work!
To keep the aircraft safe and hang 2 foot flags from the bracing lines on the truss. If the rotors strike the flag, we blow a whistle and the flight is called down. Typically more sever imbalances in the rotors get worse as the flight continues, but as long as we stop when the whistle is blown, the imbalance shouldn’t be large enough to cause a blade strike on lading. Each trim flight lasts as long as is safe, we review the footage from video cameras pointed at each rotor, we make adjustments to the trim of the blades, and then we fly again. Below is a summary of each trim flight:
Trim Flight #1-6
With Trefor at the controls we proceeded through several trim flights, each with progressively longer flight times and altitudes. Once the rotors were sufficiently balance, we attached the control canards and proceeded with two additional trim flights, until we could fly as long as desired with striking one of the safety flags.
Trim Flight #7
Todd proceeded with the final trim test, slowly bringing the aircraft up to 5 feet over a 30 second flight. The flight was not blown down, and upon landing, Atlas had only drifted a couple of feet. At this point we felt like a prize attempt was definitely within reach.
Flight #8: 2m rapid acceleration test
The best flight profile involves getting up to altitude as fast as possible and then getting back down low, where the required power is not nearly as high (450W vs. 750W). This test was an attempt at climbing faster, and would have been the last test before a prize attempt. Unfortunately with a higher initial acceleration the rotors went out of balance almost instantly and the flight was blown down.
Flight #9: Practicing with the controls
At this point we did not believe it was safe to proceed with an attempt and we only had time for one last run before we needed to be off the field. Instead we used the time to practice with the controls and maybe go for a bit more endurance. Strange behaviour of the controls, however, brought the flight down early.
Though we’re disappointed that we were unable to make an attempt at the prize, we’re extremely pleased with the progress! We’re also please with the way we proceeded in a methodical manner without putting the aircraft at risk and learned about as much as we could. If this were easy, someone else wouldn’t have already done
We’ll be working away, figuring out how to tweak the structure before coming back for another attempt in a few weeks time.