Design and build of a coaxial drone - Blog - ArduPilot Discourse
Another coaxial takes to the sky – sUAS News – The Business of Drones
T-motor X-coaxial Armset X-501 Mn501-s Coaxial Arm For Industrial Drones Motors And Foc Escs, Modularized Propulsion System - Parts & Accs - AliExpress