By Steve Manganelli
Wow, what a ride! 5th place after the first 2 days of competition, then down to 8th near the end of the last day, then up to 6th with a risky proof load and settling out at a respectable 11th out of 99 teams competing. The organizers stated that with over 800 undergraduate Engineering students participating, this was the largest Design-Build-Fly competition ever! San Diego State University Aztec Aerodesign club under the leadership of Henry (Clay) Logsdon made all their practice flights at SEFSD’s Mission Bay Park Field in the days, weeks and months preceding the April Fly off. SEFSD Safety Officer Steve Neu is their pilot and I am their Staff Volunteer Faculty Advisor.
Design Build Fly (DBF), started in 1996 as an American Institution of Aeronautics and Astronautics (AIAA) sanctioned annual competition for undergraduate Aerospace Engineering college student teams. The basic challenge is to design, then build, then fly an electric powered R/C model optimized for specific cargo missions that change every year. The course has always been the same 1000 ft oval with an opposite direction turn on the downwind leg. Myself and Steve Neu’s first involvement was in 1999 when UCSD student Andrew Mye came to an SEFSD evening members meeting and requested help/expertise in the somewhat novel at the time, discipline of electric powered R/C modeling. Andrew and his team of (4) placed 6th at our first try at the event with about 30 teams participating; Steve Neu and I subsequently guided UCSD to (4) additional top 10 finishes and the win in 2002. UCSD changed to a faculty guided methodology and Steve Neu and I migrated to SDSU in 2019. The event has gotten more and more prestigious over the years and international with at least (18) schools from abroad competing in this year’s competition.
DBF entry begins with submittal of a 5 page proposal of how a team intends to meet the mission requirements. This year, (135) proposals were submitted and the best 110 were invited to participate in the competition. Ninety nine submitted the required 60 page Report detailing their analysis and methodology leading to their final design making them eligible to compete in the flyoff April 13th through 17th. The flyoff location alternates between Tucson with Raytheon as the primary sponsor and Wichita KS with Cessna as the primary sponsor. This year’s fly off was held at the TIMPA R/C airfield in Tucson AZ. Our Aztecs’ proposal and report were ranked 25th and 29th respectively so starting in November, 2022 the adventure began.
The proposal passing muster triggered the actual aircraft design effort based on mission optimization and the scoring formula. Three of the (4) missions used normalized scoring where the school performing best at each mission gets a factor of 1 and everyone else gets a fraction of that number based on their score relative to the winner’s. It’s a bit nerve wracking as every time a new best is posted, all the existing scores go down; the written report score is a multiplier for every mission. The most intriguing mission this year was a static proofload of the center of the fuselage supported by the wing tips. This is not representative of an actual flight loading condition where the load occurs more or less uniformly along the wingspan. Simply supporting the aircraft by the wing tips is approximately a 2.5G flight load. Imagine then, what adding 150 lbs to the center of the fuselage while supported by the wing tips might be? That’s what our Aztecs did and still only garnered a 0.47 because the German team carried….wait for it, 750 lbs! I didn’t see how a single German student wrestled the 750 lbs of 12 X 12 concrete pavers in around 5 minutes but our clever Aztecs used an automotive floor jack to lift their exercise weights into position.
The German team from RWTH Aachen University built a wing with anhedral and their loading fixture kind of “post-tensioned” it as it was loaded allowing it to carry more weight not unlike a masonry arched bridge where the loading components are in compression.
The next most interesting aspect of the mission is each one had to start from the aircraft in an airline baggage legal size container and be assembled ready for flight by one Student in less than 5 minutes or less than 10 minutes when the static proofload was part of the Mission. Our creative Aztecs designed a pod and square boom fuselage where the boom retracted into the fuselage up to the firewall and then locked when deployed with a typical canopy latch. Wires to the elevator and rudder servos stayed connected to the RX during all conditions. The next obstacle set forth by the organizers is the requirement to have 2 interchangeable sets of wings. Two coin flips just before your turn to fly selected the left and right panel from the set of (2) which both had to fit into that same airline size box. Master assembler of our team Max Dommers, calmly withdrew the 4 wings from the box and set them aside, then pulled out the fuselage and extended the tail boom. The MLG was attached with (2) thumb screws and then the fuselage set on it’s wheels. Next the wing joiner was installed into the appropriate wing and then slid into the fuselage, the other wing was next slid on and the two held inboard with a rubber band. The aileron wires were next connected and the motor battery was installed. Lastly, the prop adapter and prop were installed. Max had this down to about 3 minutes which was necessary as the other normalized missions added installation of a payload to the 5 minutes!
The intermediate payload was a weight having dimensions at least 3” X 3” X 6”, amount of the teams choosing however the mission score depended on the product of the payload weight and the number of laps that could be flown around the course in 10 minutes. Steve Neu expertly piloted “Huitzilopochtli” (Aztec Left Hummingbird God) (12) laps around the course in the allotted time and put a nice score on the board for us.
The final heinous mission was to carry a simulated jamming antenna in the form of ½ inch schedule 40 PVC pipe, the length of the teams choosing as long as it fit into the box. Oh yeah, it had to be carried on the wing tip toward the inboard side of the course! The teams were allowed a counter weight on the opposite wing tip but not a “counter drag” the pilot simply had to deal with it. Both pipe and counter weight had to be installed within the 5 minutes. Max expertly put it together in under 5 minutes and Steve Neu expertly piloted Huitzilopochtli around the course for 3 laps in about 2 minutes carrying a 24” inch (pipe) antenna.
At the end of the flight, he pronounced the aircraft too tail heavy and pitch unstable to risk more points with a larger length pipe and the decision was made to save the plane for the proof load mission. Our first successful proof load of 85 #s kept us in 8th place but Max calculated that 150 (which is more than we’d ever tried) would put us up to 6th place! The go-for-broke (literally) load was successful and we moved up. All we had to do was wait out the teams yet to fly after us and hope none of them did anything better than us. Of course those immediately below us tried to do the same thing and (3) teams overtook us. Embry-Riddle-Prescott whom was missing a mission score late in the contest zoomed up to 7th from 25th once they completed their pipe/antenna flight. The clock timed out and we happily took our well deserved 11th place finish. Congratulations to 1st Place RWTH University Aachen (Germany), 2nd Place University of Ljubljani (Slovenia) and 3rd place Embry Riddle Daytona Beach Campus. For detailed results and more information, go here : AIAA Design/Build/Fly | AIAA . All in all a cherished opportunity for SEFSD to support our future Aerospace Engineers.
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