May 4, 2016
Aerospace engineering Longhorns gave it their all at this year’s international Design/Build/Fly (DBF) competition, landing 13th place among more than 80 competing universities. The event was hosted by Cessna Aircraft Company/Raytheon Missile Systems and the American Institute of Aeronautics and Astronautics (AIAA) on April 15-17 in Wichita, Kansas.
The annual event is an opportunity for students to test out their classroom knowledge and engineering skills by designing, building and demonstrating their aircraft’s capabilities while competing against other schools. The goal, according to the DBF website, is to for students to create a “balanced design possessing good demonstrated flight handling qualities and practical and affordable manufacturing requirements while providing a high vehicle performance.”
This year’s competition consisted of three flight missions and one ground mission, and was unique from previous years because it called for two aircraft – a manufacturing support aircraft and a production aircraft made of sub-assemblies. Each flight mission had to be completed in order and teams could only move on to the ground mission once they successfully completed the requirements for mission two.
Designing and Building
About 30 aerospace engineering undergraduate students began working on the project last fall. UT DBF President Travis Minikus said that the group, which was divided into propulsion, structures and aerodynamic teams, had more pressure and time constraints this year because they had to build two airplanes instead of one. He said they consulted more with their advisors, particularly ASE/EM staff member Mark Maughmer II.
It was important to seek guidance, he said, because they couldn’t afford to go in the wrong direction due to the amount of time they had to build their two aircrafts, Tammy and Stacy.
The UT manufacturing support aircraft, known as Tammy, was designed to carry the production aircraft for one of the specified missions. It measures 5 feet wide with a wingspan of over 4 feet, is 5 feet long from propeller to tail, and is close to 2 feet in height. The production aircraft, referred to as Stacy, was designed to be smaller and lighter, so that it could be placed inside Tammy for mission two.
Flying
Once at the Cessna field, the team unloaded their bus, determined to complete the missions and demonstrate their months’ long work and the two airplanes’ flying capabilities.
After a couple of attempts – and repairs in between – Tammy finally completed the first flight mission, making three full laps without carrying a payload within five minutes.
The second flight mission required teams to fly the production aircraft inside the manufacturing support aircraft within 10 minutes. The number of laps required was based on how many sub-assemblies the production incorporated. Since Stacy was a one-piece aircraft, UT was only required to fly one lap.
Minikus said that in order to fit Stacy inside of Tammy, they designed the production aircraft with an inverted V-tail to avoid large pieces of dead space once it was placed inside Tammy. They also made Tammy’s fuselage zippable. Once Stacy was tucked inside, its balsa and plywood wings fit into the holes cut out of Tammy’s foam wings.
In the final flight mission, Stacy was required to complete three laps while carrying a 32 oz. Gatorade bottle internally within five minutes. After some issues with landing gear repairs and a first failed flight, the Texas team finally completed the last mission successfully.
Lessons Learned
The competition didn’t go without its trials. The Texas team faced strong winds and had to reattempt mission one and two because Tammy’s engine didn’t have enough engine power to overcome the 30 mph winds. Minikus said that they were up late two of the three nights running motor and battery analysis to increase the engine power.
Another problem they faced in the final mission was the realization that Stacy’s landing gear was crooked. They flew the airplane in the third mission but were unable to take off within the 100 ft. limit. The crooked landing gear caused Stacy’s fuselage to tear as it landed. They rapidly fixed the fuselage and landing gear before flying the mission successfully a second time.
Even with all of the challenges and multiple mission flight attempts, Minikus said the UT team pulled through in the most difficult times of the competition and never thought of giving up.
“None of our airplanes broke and that made me so happy,” he said. “Even though we had to reattempt every mission, every single time, we managed to fix the problem and get things working again.”
Working on this year’s competition, he said, gave them more options to continue building in the future.
“We were challenged to use materials we’ve never used before and that helps our knowledge base, which can be passed down each year,” Minikus said.
