Date: 202102
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Helicopter
Operator: Military
Flight plan: VFR
Mission: Training
Flight phase: Takeoff / Launch
Airspace: Class D ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: Cessna Single Piston Undifferentiated or Other Model
Reporter organization: Government
Reporter function: Ground
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness; Confusion
Second reporter function: Local
Anomaly: ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Air Traffic Control; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: A flight of 2 helicopters called Ground Control on for VFR flight following. They were on a non controlled ramp. Ground Control issued departure frequency and squawk. No readback was heard. Generally; this is an issue with military helicopters; and they usually call up local shortly after; when ready to depart. I reached out several times on Ground Control; inquiring if they had the ATIS information; and if they wanted to taxi to a runway or a present position departure. They were non responsive.I passed the strip to Local Control; thinking they would call him. Moments later a Aircraft Y who had been in the pattern was departing and I saw the 2 helicopters departing the ramp; right in the path of Aircraft Y. I alerted Local Control and he had the Aircraft Y make an evasive left turn to avoid the traffic. Both Local Control and myself on Ground Control made multiple attempts on all frequencies to reach the Aircraft X flight. They both almost had a NMAC with the Aircraft Y. TRACON was calling on the shout line and I answered on Ground Control as Local Control was trying to move the Cessna to a safe position. The TRACON controller alerted me Aircraft X had called them and they mistakenly thought they were calling from a different airport so the TRACON controller gave them a departure clearance which resulted in the unauthorized departure from ZZZ and the NMAC. Once Aircraft Y was safe Local Control and Ground Control both advised TRACON to issue a brasher.Military helicopter pilots need better training on how to depart here and learn to give appropriate readbacks. TRACON should have verified where the helicopters were. Assuming they were at ZZZ1 created a dangerous situation. The VFR flight plan was in the system. TRACON Flight Data should have seen it originating from ZZZ.


Second narrative: Aircraft Y departed climbing to remain in closed traffic for stop and goes.  Aircraft X helicopters on a ramp near the departing Aircraft Y began to lift climbing in front of the Aircraft Y who did not have them in sight. Local Control issues immediate traffic for the Aircraft Y and told to turn left immediately. Local Control called out to Aircraft X on Local Control frequency several times and on guard frequency.  Aircraft X did not answer and continued to fly toward Aircraft Y which was maneuvering to avoid the helicopters. Aircraft Y made an inadvertent low altitude turn to avoid colliding with the helicopters. Coming out of the turn the Aircraft Y reported them in sight.Approach Control called Local Control in a panic about Aircraft X saying she gave permission for departure to the helicopters saying she thought they were at another airport nearby. She did not know they were actually located at this airport. Aircraft X continued toward the Aircraft Y and eventually called local control once they departed the airport.  Local Control told Aircraft X that they were not cleared by Local Control for departure and advised that they almost hit Aircraft Y that was climbing directly toward the helicopters.Aircraft X replied that Ground Control gave them the departure frequency.  In error Aircraft X thought that they needed to contact Approach for takeoff from the airport.  When Aircraft X called for VFR departure; Ground Control issued Aircraft X a squawk code and told them the departure procedure which is normal handling for VFR aircraft.  The next expected sequence of events is that the VFR aircraft then contacts Local Control for takeoff clearance. Aircraft X bypassed Local Control and went directly to Departure Control thinking that is who they needed for departure.My recommendation is that there is clarity made to pilots that their receipt of the departure frequency is not a directive to contact them to depart while the Tower is actively controlled by a Local Controller who is issuing control instructions and safety alerts.


Synopsis: Tower Controllers reported a flight of two helicopters departed from the ramp without clearance from the tower and had a NMAC with a departing aircraft because Ground Control mistakenly issued them a TRACON frequency which cleared them to depart thinking they were at an adjacent airport.