This project presents a fully custom 8 kg autonomous multirotor platform developed for the 2025 C-UASC competition. Designed for efficient propulsion, endurance, and autonomous payload delivery, the system integrates 22-inch propellers, a vibration-isolated avionics bay, detachable carbon fiber arms, compliant landing gear, and a motorized payload winch.
Learn more about the mission at polyuas.org
The airframe consists of two primary modules: a rigid external flight frame built from aluminum and carbon fiber, and a vibration-damped avionics bay for critical electronics and batteries. The arms are carbon fiber tubes bonded to printed mounts using epoxy for high stiffness and quick removal during transport. Hand calculations and FEA confirmed a high factor of safety under maximum thrust loads, validating the structural efficiency of the design.
Figure 1: Complete CAD rendering of Shadowfax the autonomous package delivery quadcopter.
Figure 2: Vibrationally damped avionics bay.
Figure 3: External frame structure.
Figure 4: Motor mount connected to carbon with epoxy.
Figure 5: Modular arm with dowel pin release.
Payload capacity plays a critical role in determining its flight range and endurance. We designed the aircraft to be capable of flying with a 0.5 kg payload for extended periods. Our 8kg AUW aircraft utilizes four KV320 brushless motors paired with 22-inch bi-blade carbon fiber propellers. Two bladed propellers with a 6.6” pitch were selected to operate efficiently in low free-stream velocity conditions. This propulsion system provides almost 5kg of thrust per motor, as shown in Figure 6, giving us a total thrust to weight ratio of almost two to one. This propulsion configuration gives us more flexibility in the mechanical design of our aircraft and allows for larger payloads in the future.
Figure 6: Thrust vs. RPM for 22-inch propeller and KV320 motor captured with Tyto Robotics thrust stand.
Figure 7: Thrust stand test configuration. Motor is covered with tape for optical RPM sensor.
Figure 8: Avionics connected to power assembled outside of aircraft.
Flight Controller: Cube Orange+ with triple-redundant IMUs, dual barometers, and integrated vibration isolation for stable autonomous control.
Autopilot: ArduPilot with Mission Planner GCS.
Command & Control (C2): Herelink 2.4 GHz for MAVlink telemetry, RC and video transmission.
Navigation: Here3 GPS with RTK.
Optics: GoPro Hero 5 Black.
Power: 6S 22,000 mAh Lipo battery with COTS power distribution board.
Structural components were 3D printed from PPA-CF and ASA for strength and heat resistance. The carbon fiber arms were cut to length and epoxied to the motor and arm mounts to form the main frame (Figure 9). The central pod plates originally used carbon fiber but we accidentally ordered uniaxial weave and quickly discovered that our parts snapped laterally after we waterjet them. We pivoted to aluminum since it was the best alternative we had on hand. After verifying fit and alignment, motors, ESCs, and landing gear were installed, with wiring routed internally through the arms. The assembled prototype (Figure 10) was tested for structural integrity, vibration isolation, and electrical continuity before inserting the avionics stack.
Figure 9: Printed assembly with printed sandwich plates.
Figure 10: Assembled aircraft with some prototype parts.
Figure 11: Myself epoxying motor mount to connect carbon rods.
Weeks of flight testing was conducted to ensure safe aircraft operation and mission capabilties. I led all flight efforts and piloted from full acro mode to operating missions.
Video 1: First flight and crash due to excess yaw.
Video 2: First autonomous mission!
Placed 3rd in mission demonstration and design review.
Participating institutions included: Cornell, IIT-Bombay, Cal Poly SLO, Cal State LA, San Diego State and CSU Bakersfield.
Figure 12: Competition team photo with aircraft.
Figure 13: Preparing for flight at the compass rose at Mojave Air & Space Port. Conditions were 95 degrees Farenheit and light wind.
Figure 14: Safety review with judges.
Figure 15: Shadowfax in flight!
During the waypoint navigation mission, we decided to push the envelope and command 10 m/s aircraft velocity. There was also a unit conversion issue in the mission planning that caused the aircraft to go to 100m instead of 100 ft. These factors caused the autopilot to initiate an emergency RTL due to critical thrust loss. When the aircraft came home, it was also having GPS issues, which caused a slow spiral down. After the first impact, which reported 10 g from the FC accelerometer, the aircraft bounced 20ft into the air, so I switched to ACRO mode and landed it safely. I disarmed the aircraft, and one of the arms fell limp onto the ground. This clearly meant that the first impact broke the arm, and the thrust force kept it intact for the secondary landing.
We were able to fix the arm and avionics box with epoxy and JB Weld. One of our transmission cables was also sheared in half so we had to solder the coaxial cable together during the competition. Our team flew two more missions and finished third.
Figure 16: In the field repairs after 10 g crash. Fixed aircraft structure and soldered a coaxial cable then competed in the two remaining flights.
Figure 17: Flight log showing motor RC control to troubleshoot hardware thrust loss error.