What happened
On August 7, 2020, an Aviat A-1 Husky, registration SP-AIR, was parked on the general aviation apron at EPMO airport. The pilot initially contacted EPMO Tower and was instructed to contact the Delivery frequency to obtain weather information and flight clearance. After receiving the necessary weather data and clearance from the Delivery controller, the pilot was instructed to contact EPMO Tower again.
Upon switching back to the Tower frequency, the pilot attempted to establish contact. While the Tower controller could hear the pilot, the pilot was unable to hear the controller's responses. Despite several attempts by the pilot to re-establish communication, the connection remained one-sided. The controller attempted to reach the pilot using a backup radio station and the Delivery frequency; while a brief two-way exchange was achieved, the communication link was lost again shortly after.
During this period of communication failure, the airport Duty Officer, while conducting a maneuver area inspection, observed SP-AIR taxiing from the general aviation apron onto taxiway "S". The Duty Officer notified EPMO Tower of the movement. Once the aircraft reached taxiway S, the pilot successfully established two-way radio contact with the Tower. The controller informed the pilot of the previous failed communication attempts and noted that the aircraft had started its engine and entered the taxiway without authorization. The pilot apologized, citing poor audibility, and stated they believed they had already received the required clearance. The remainder of the taxi and takeoff procedures were completed correctly.
The investigation
The PKBWL examined the sequence of radio communications between the pilot and the various controllers, as well as the observations made by the airport Duty Officer. The investigation focused on the breakdown in communication and the pilot's decision to proceed with engine start and taxiing without confirmed authorization.