Center Controllers working unfamiliar TRACON airspace issued a clearance to an aircraft which placed the aircraft below the Minimum Vectoring Altitude.
Synopsis
Center Controllers working unfamiliar TRACON airspace issued a clearance to an aircraft which placed the aircraft below the Minimum Vectoring Altitude.
Narrative
Normally; our airspace is only working 110 and above during non-mid operations. However due to maintenance at ZZZ approach; we were taking over their airspace down to the ground. This is a very unfamiliar situation to start out with and led to confusion as well as increased complexity since we normally do not work this airspace. Aircraft X was practicing IFR approaches at a couple of airports within ZZZ approach. They were heading back to ZZZ airport; where they originally departed from. They were at 040 and wanted to practice the VOR XX approach into ZZZ. However; they wanted to hold over the ZZZ VOR first; which is the missed approached for the VOR XX. I asked them if they wanted to hold at ZZZ on their inbound heading or fly the published missed. They said the published missed holding pattern. I then cleared them to fly the published missed approach hold for ZZZ VOR XX approach. I never gave them an altitude to hold at and thought they would just do it a 040. However; once they established in the hold; they descended on their own to 024; which is the published altitude for the missed holding; but is below our MVA for that area. I was not expecting them to descend to that altitude but understand why they did after the fact. Recommendation: I think the only recommendations I would have would be for more training on working approaches. We usually do a refresher twice a year; but outside of this many do not work approach airspace unless they work a mid. It is just a foreign area that causes a lot of confusion and also attention while also working our normal busy traffic into ZZZ2 and ZZZ3 .We also could have just split out ZZZ approach on its own; as we have an extra scope we could use. This would have allowed someone to have 100% focus on just that airspace.
Second reporter narrative
Aircraft requested to hold at ZZZ as published on the VOR XX approach into ZZZ airport. After the hold the aircraft wanted to fly the VOR XX approach. Controller told the aircraft to hold at ZZZ as published. The aircraft was at 4000 ft MSL; the missed approach procedure was at 2400 ft MSL. The aircraft descended to 2400ft MSL. I believe there was a misconnect between the pilot and controller. The controller told them to hold as published but did not clear them to 2400. The pilot obviously thought they were cleared to descend to 2400 since that was the published missed approach procedure. Because the controller did not clear the aircraft for the approach; they were not cleared to leave 4000 ft. Then the relieving controller took over the sector when the aircraft was in the holding pattern at 2400 and was confused on whether or not he could issue an approach clearance below the MVA; so he told the pilot in order to give a clearance he would need to climb to 3000 ft and report reaching it. I was the instructor training on the other side.Recommendation: When a center sector takes over an approach control due to a planned outage/maintenance we should practice in labs approaches before assuming control. This is especially important for controllers who do not work midnight shifts and rarely work this flow of traffic. I understand we do refreshers on these things in the labs already once a year; but when there is a planned outage we need a refresher for all controllers prior to taking the airspace.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.