Date: 202105
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Robinson R22
Operator: Personal
Operating under: Part 91
Mission: Training
Flight phase: Taxi
Reporter organization: Personal
Reporter function: Pilot Not Flying; Instructor
Reporter qualification: Flight Crew Rotorcraft; Flight Crew Flight Instructor; Flight Crew Commercial
Human factors: Communication Breakdown; Situational Awareness
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Detector: Person Other Person
When detected: Aircraft In Service At Gate
Result: General None Reported / Taken
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: During the final minutes of a long training lesson of emergency procedures my student and I were hovering at the departure end of Runway XX. We had just finished our last emergency procedure training pattern and were ready to head back to the ramp to stop our lesson. Where we were located; we needed to cross Runway XY/XZ to get to the ramp on the east side of the airport. Since my student is getting ready for a check ride and I am very comfortable with both her flying and communication skills with ATC I left it up to her how we would reposition. Due to the light wind an air taxi crossing the field and Runway XY/XZ was both appropriate and her final decision. She keyed up the mic on tower frequency and requested the air taxi back to our ramp as she; and others at the school; normally do many times a day. Unfortunately; the first transmission was blocked by additional traffic on frequency and her request did not go through. She knew this occurred since she heard the end of the other traffics transmission; and ATC was advising that traffic that we were still on the runway. Once there was silence on the tower frequency; she made her request again. The next thing I heard was a traffic report from ATC advising her of an additional helicopter about two miles to the west and inbound to the same location we were going. My student acknowledge the advisory and advised we would be looking for that traffic as she started to proceed to air taxi to the ramp crossing Runway XY/XZ. Just as we were about to cross XY/XZ we heard an advisory from ATC that an airplane was cleared for takeoff and as the pilot was acknowledging his clearance; he inquired what the little helicopter was doing (us). I thought it was weird of the clearance for takeoff since we were in the process of air taxing and about to cross the runway. Once past the runway and starting to land; ATC inquired with my student if she requested to cross Runway XY/XZ and she replied yes (thinking her transmission was received and by ATC giving her the traffic advisory he was aware of our movement). Unbeknownst to her or I; her second transmission was also walked on and not received by ATC. My student took the coincidental advisory of traffic as ATC's acknowledgment that we were intending to air taxi and cross Runway XY/XZ. It was confirmed upon landing by someone listening to ATC that neither of our requests had gone through. ATC had not heard her first or second transmission for the request and the traffic advisory was merely coincidental looking back on it. Luckily the traffic that was advised they were clear for takeoff on Runway XY had not even started rolling at the opposite end of the runway for their takeoff and they had also seen us and not started rolling until we past the runway.Looking back on the incident I know as an instructor I CANNOT let comfort and confidence with a student lead to complacency. I need to be on top of my game 100% of the time and make sure both myself and my student is both listening to and understanding radio traffic; and if we do not; we need to make sure we completely understand and get clearances before moving. This had the potential for a worse outcome and I most definitely have learned from it. I need to keep my eyes and ears 100% concentrated on the task at hand; and looking back on it I know my mind was still partially concentrated on our last emergency procedure training and how to debrief my student about it; and not on the 'simple' task of taking the helicopter back to park it. Complacency has no place in the cockpit and this event has taught both my student and I a valuable lesson.




Synopsis: Helicopter Instructor reported a runway incursion occurred when the student air taxiied across the runway while traffic was waiting to take off. Instructor stated they did not realize the student's requests to ATC for crossing were blocked both times.