DA40 Diamond Star
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4.0
Physiological - Other; Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Staffing; Environment - Non Weather Related; Human Factors
The operation was combined in the tower. I was working radar from the D-Brite radar display at the Local Control position. I had just switched an aircraft to the tower on an approach to stay with the tower in closed traffic. I was told from the controller giving me the position that Aircraft X was on a 340 heading from the south for the ILS option. I turned Aircraft X to a 010 heading then immediately had to use the restroom. I could not wait. The other controller in the tower with me at the time and I made a split second decision to let me run down to the tower break room to use the restroom. I was gone for no more than 3 minutes. When I came back; Aircraft X was about a mile west of the airport at 2;400 feet. The controller working the tower tried to transmit to Aircraft X but then remembered he did not have the radar frequencies keyed up. I immediately told the pilot to climb to 3;000 feet and to continue on his current heading because there was someone in the pattern. Aircraft X ended up passing behind the aircraft on approach and was well above him. When I asked the student pilot what they were doing they said they were on the VOR-A approach. The instructor pilot keyed up and said they were on the approach but were never given any circling instructions. I told him he was never cleared for an approach to begin with. They eventually made the decision to go back to their departure airport instead of coming back to try another approach.There is no way to prevent this specific situation from happening again; unless a bathroom is put in the tower cab.
During our initial contact with Approach Control; we requested the VOR-A approach. However; we began receiving vectors for the ILS Approach. We did not realize this discrepancy. Since the vectors that we were given for the ILS were similar to the ones we would have received for the VOR-A; we incorrectly assumed we could expect the VOR-A approach. Our most recent assigned vector was a heading of 010 degrees which lined us up perfectly in-between the initial/final approach fix for the VOR-A and the airport (just as would have happened had we been actually receiving vectors for the VOR-A approach). The only abnormality was the intercept angle to the final course was 84 degrees; but this would not have been the first time I had received a non-standard (more than 30 degrees) intercept angle; so I did not think anything of it.Since we thought we were being vectored for the VOR-A approach and nothing seemed unusual; we made a second false assumption that we had been cleared to intercept the final approach course and subsequently cleared for the approach. Therefore; we turned to intercept and began descending to the MDA. After a few moments; I realized something wasn't right because we were getting very close to the airport and hadn't received any circling procedures yet (The VOR-A requires a circle-to-land approach). Thinking that maybe the Control Tower was the one that would give us the procedures and that maybe Approach control forgot to tell us to change frequencies; I began to change the radio over to the tower frequency. Before I could finish; Approach control realized we had diverted off our 010 heading and assigned altitude. We were instructed to climb to four or five thousand immediately. When the controller asked what we were doing; I explained that we were flying the VOR-A but had never received circling instructions. They responded by saying we weren't cleared for the approach and that we were supposed to fly the ILS instead. This was the first time that I realized we had gotten vectors for the wrong approach. Knowing that it would be too hard to explain what had happened over the radio; I asked for a phone number that I could call after we had landed.When I called the phone number later; I spoke to the initial controller that we had contacted (The one that we requested the VOR-A to; but not the one that gave us the vectors). They explained that when we had requested the VOR-A; they mistakenly had written down 'ILS' on their scratch-pad. This is probably because most airplanes fly the ILS and I would imagine very few to none request the VOR-A. Because they had written down 'ILS' the other controller; thinking we wanted the ILS approach; began giving us vectors for the ILS. At one point this second controller told us what approach we were getting vectors for; but we were so fixated on the VOR-A that we assumed we heard 'vectors for the VOR-A.' Whether or not this is what was said I do not know.Nevertheless; after the controller gave us the 010 heading; the controller left their station (according to the first controller whom I talked to on the phone) for a few minutes. During this time we made our deviation from the heading and began flying the approach. The only other two controllers on duty did not realize this deviation as the radar tracks with another airplane were overlapping (according to the controller on the phone). ATC did not realize we had deviated until a few minutes later when the second controller returned to their station and saw our mistake. This was the same time I had recognized the mistake and was about to call the control tower.Despite the miscommunication with ATC during the initial contact; despite the vectors lining us up with the VOR-A approach; despite the controller leaving their station as we made our mistake...the problem was our mistake. We shouldn't have flown the VOR-A approach without confirming that we had been cleared for it. Even if we had been receiving the correct vectors; we still needed an approach clearance.The first hint was when the controller told us what approach we were receiving vectors for; but we were too fixated on flying the VOR-A approach to catch it. The second hint was the non-standard intercept angle to the final approach course; but it wouldn't have been the first time I had to do a very sharp turn onto a final course. The third hint of the problem was when we had gotten close to the airport without being told to contact tower. I caught the mistake on this third hint; but it was very progressed by that time.
A Controller and a flight instructor reported that an aircraft assigned a vector for one approach intercepted and began descent on a different approach. The controller did not immediately notice because they left their control position to go to the bathroom.