Date: 201311
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: ATR 72
Operator: Air Carrier
Operating under: Part 91
Mission: Ferry / Re-Positioning
Flight phase: Taxi
ATC / advisory: Ground ZZZ; Ramp ZZZ
Reporter organization: Air Carrier
Reporter function: Lead Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Training / Qualification; Confusion; Communication Breakdown; Situational Awareness
Anomaly: Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Taxiway
Detector: Person Maintenance
When detected: Taxi
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Police / Security Involved
Contributing factors: Procedure; Manuals; Airport; Human Factors
Primary problem: Ambiguous

Narrative: The assigned aircraft which required a 1A Check and 4A Check Inspection; was parked at the gate. The other Mechanic was sitting left seat and I was sitting right seat. We started our checks requiring aircraft power. Needing to relocate to the west hangar to conduct the inspections; the left seat pilot proceeded to contact Ramp Tower to ask for permission to taxi to the hangar from our gate requesting a progressive taxi. A Ramp Tower Agent replied; 'Request approved taxi at your discretion.' I told the left seat pilot to ask for permission to taxi via November to Alpha to the hangar. Ramp Tower responded again by saying; taxi at your own discretion to the hangar. Giving us the OK to taxi; the taxiing mechanic proceeded to taxi to the hangar via November to Alpha. After turning left on Taxiway Alpha; heading to the hangar; we both noticed another company aircraft taxiing from the west hangar turning our way onto Alpha. I told the taxiing Mechanic to slow the aircraft and hold short at Taxiway Victor so the aircraft heading to us could turn off. After doing so he contacted Ramp once again to inform them of the other aircraft headed our way. Ramp Tower response was; 'they didn't contact me.' Noticing a yellow security vehicle turning from the vehicle driving lanes out onto the taxiway; blocking any further advancement to our destination; the taxiing Mechanic again contacted Ramp Tower; informed them that something was wrong and described the security vehicle blocking our way. At that point she suggested we contact ATC. He contacted ATC and they told him to proceed to our destination then contact them again upon arriving. After the other company aircraft cleared Taxiway Alpha; the aircraft proceeded to taxi to the hangar. After arriving; the taxiing Mechanic contacted ATC and obtained a phone number to call about our experience. He called Ground and they informed us that we had indeed committed an airport deviation. The security vehicle driver asked us for our information and informed us that we were actually taxiing the aircraft illegally when in all actuality we thought we were OK. Not once did the Ramp Tower Agent we were talking to on the radio inform us to switch frequencies until we told her about the security vehicle. We were also informed by the security vehicle driver that we needed to complete a course held by airport authority before ever taxiing any aircraft at the airport. This is something that we were not aware of.Also the person we requested the progressive taxi from; obviously did not know to tell us to switch frequencies. If someone had told us to switch over to ATC before taxiing on November; this would not have happened.




Synopsis: An ATR-72 Maintenance crew which had not attended the Airport Authority training; taxied from a company ramp with Ramp Tower permission; but did not contact Ground Control and were stopped by a security vehicle enroute to a maintenance hangar.