Light jet pilots reported a low altitude alert from ATC on descent into BJC.
Synopsis
Light jet pilots reported a low altitude alert from ATC on descent into BJC.
Narrative
I was the pilot monitoring the flight and primarily had the radios. While on descent into BJC for a visual approach; we had been given several step-down altitudes and direct to the final approach fix as we got near the airport. I coordinated with the pilot flying for him to briefly take the radios while I contacted the FBO to confirm that they knew of our arrival in about 10-15 minutes. While I was talking to the FBO; I saw the pilot flying talking on the radio and dial 10;000 feet into the altitude window and continue our descent from about 14;000 feet. After finishing with the FBO; I switched back to Denver approach; and confirmed with the pilot flying that we were now descending to 10;000 feet. At approximately 10;300 feet; ATC issued us a low altitude alert and told us to climb immediately to 11;000 feet. The pilot flying disconnected the autopilot and began a climb; while I set the flight guidance panel to 11;000 feet. A few seconds later; before reaching 11;000; ATC issued us a descent to 9;000 feet. We complied with the new ATC instructions and completed the rest of the approach with no issues. After landing; the tower controller at BJC advised us of a possible pilot deviation and gave us a phone number to call. The captain/pilot flying called the number; and we completed our next flight to ZZZ without issue. We were in night VMC conditions for the entire event; and we received no EGPWS (Enhanced Ground Proximity Warning System) warnings or alerts.Suggestions: I cannot precisely say where the breakdown of communication happened; since I was not monitoring the Denver approach frequency during the event for the 30 seconds I was contacting the FBO. It's possible for ATC to have erroneously assigned us a lower altitude than MVA; especially since we were turned off of the arrival with the direct to the FAF. It's also possible that the pilot flying erroneously put in an incorrect altitude; misheard an instruction; or other similar errors. To help prevent this; I can try to contact the FBO via another means of communication to help make sure there are two of us listening during the final several minutes of a flight.
Second reporter narrative
We were on the POWDR 1 arrival and were told to cross POWDR at 14;000 at 250KTS. After we crossed POWDR we were cleared direct to ALIKE; the non flying pilot was on com 2 talking to the FBO and the controller cleared us down to 10;000. I put 10;000 in the altitude selector and pointed; descended to 10;000 from 14;000. The non flying pilot came back to com 1 and we were about 10;300 when the controller told us there was a low altitude alert and to immediately climb to 11;000. We got to 10;700 and then they cleared us to 9;000. After we landed we got the number from the ground controller to call approach control when we go to the FBO. I called them and explained what I heard; the controller said he was reviewing the tape and would get back to me if they needed more information
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.