On October 7, 1921, a serious accident took place at the Mareilles military airfield. The incident involved Lieutenant de Payer, who was conducting a test flight of an experimental aircraft at the time. Though the aviator survived the accident, he sustained injuries, primarily to his head and left arm. The cause of the crash was attributed to a defective design of the aircraft, which was a hybrid machine combining features of both a helicopter and an airplane. The aircraft was equipped with two distinct propellers—one for vertical lift and another for forward motion—making it a unique and complex design for the era. The accident occurred shortly after takeoff, when the aircraft structure broke apart into two parts. This scenario was eerily similar to a previous crash that had taken place in March 1921 during an earlier test flight of the same type of aircraft. The earlier incident had also involved a failure in the aircraft's design, raising concerns about its stability and safety. Despite the severity of the crash, Lieutenant de Payer emerged unharmed, though he suffered contusions and other minor injuries. In contrast, the pilot of the aircraft sustained more serious injuries, including five fractured ribs. The incident highlighted the risks associated with experimental aviation technology and underscored the need for further development and testing of such hybrid aircraft before they could be deemed safe for use. The crash at Mareilles served as a sobering reminder of the challenges faced by early aviation pioneers. At the time, the field of aviation was still in its infancy, and many of the technologies used in aircraft design were unproven. The failure of this particular aircraft design to perform reliably during test flights pointed to the need for more rigorous engineering standards and safety protocols in the rapidly evolving world of flight.