Agusta Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 25; Flight Crew Total 3200; Flight Crew Type 200
Communication Breakdown; Situational Awareness
Conflict NMAC; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Separated Traffic; Flight Crew Took Evasive Action
Human Factors
Near miss occurred when departing from the hangar at a tower controlled airport. Sequence of events leading up to the near miss are as follows: aircraft requested taxi and departure to the NE. Tower acknowledged and cleared the aircraft to taxi as requested. Aircraft taxied out; completed takeoff checks and departed. After takeoff ATC Tower made immediate evasive maneuver calls to prevent a collision with other traffic that had recently departed.This close call was a clear case of a pilot requesting a clearance and hearing the clearance that he was expecting; not the clearance that was actually given. Tower gave a taxi clearance and a taxi clearance only. At no time did the tower say 'cleared for takeoff'. The pilot was expecting the Tower to issue a taxi and takeoff clearance in one transmission; but only a taxi clearance was given. [Aircraft] took off without ever hearing or receiving a 'cleared for takeoff' in their clearance.
AW-139 helicopter pilot reported an NMAC when they took off without clearance.