What happened
On October 29, 2009, at approximately 14:45 local time, a Bell 412 EP helicopter, registration EC-KGZ, operated by Inaer, was performing a takeoff from a parking position at Granada Airport. The aircraft had recently completed a search and rescue mission and had stopped at the airport to refuel.
After notifying the tower that the crew was ready to taxi, the pilot began positioning the helicopter into a hover. During the communication process, the pilot misinterpreted a question from the air traffic controller as an authorization to depart, cross the runway, and proceed north. Believing he had clearance, the pilot applied power and began a right turn with a nose-down attitude, gaining translational speed.
Upon realizing that takeoff had not been authorized due to approaching traffic on final approach, the pilot instinctively applied cyclic input to brake the aircraft. This sudden maneuver caused the helicopter to oscillate heavily on its transverse axis, resulting in the tail rotor and tail guard striking the ground. The pilot, believing only the tail guard had made contact and noting no unusual vibrations, continued the flight to the base, only discovering the damage to the tail rotor after landing.
The investigation
The CIAIAC examined the cockpit communications and the sequence of events leading to the impact. The investigation focused on the interaction between the pilot and the air traffic controller (TWR) regarding the use of standard phraseology. The investigation also reviewed the aircraft's flight path and the physical damage sustained by the tail rotor and tail guard.
Findings
- The primary cause of the incident was the misuse of aeronautical phraseology by the controller, specifically the use of the word "can" (¿puede...?) in a way that the pilot interpreted as an authorization.
- The pilot's excessive haste in initiating the takeoff maneuver, beginning as soon as the "ready to taxi" message was sent, contributed to the event.
- The pilot's misinterpretation of a question as an instruction led to the unauthorized crossing of the runway and the subsequent aggressive maneuvering to stop the aircraft.
- The pilot failed to identify the damage to the tail rotor immediately after the strike because the impact was not accompanied by noticeable vibrations, which allowed the aircraft to continue flying in a potentially unsafe condition.