Corporate jet flight crew reported receiving a low altitude alert from ATC on the descent into HCR.
Synopsis
Corporate jet flight crew reported receiving a low altitude alert from ATC on the descent into HCR.
Narrative
We were cleared to hold at zangy fix on the RNAV GPS A into HCR in VMCconditions at 14000 ft due to company traffic doing the same approach ahead of us and a very busy uncontrolled aerodrome with lots of VFR traffic around. After entering holding ATC cleared us for the approach before completing one turn in the hold. Once cleared for the approach I set the altitude alerter to the final approach fix / uzeyu to cross at 9400ft. When we were cleared for the approach; I went VS mode to fly the plane from 14000 ft to cross zangy at 11000ft with FMS guidance (preselected at 11000) and I activated VNAV and approach mode. However; neither of us remembers if the VNAV captured correctly because it was an extremely busy uncontrolled field with lots of VFR traffic around at the same time. As I was established on the final approach course before reaching zangy I realized the plane did not capture the FMS VNAV descent with the level off at 11000ft and went down to 10500ft. I corrected immediately using Control Wheel Steering (CWS) to fly the plane back up to 11000ft. At this moment ATC issued a low altitude alert. We continued the approach normally with crossing all published altitudes. Once the airport was in sight we canceled IFR and landed. It was a very busy moment and time where we had to hold; listen to local VFR traffic; using the automation. What I have learned from this and going forward is to make sure that I verify each FMS altitude in the box and also point out its correct magenta altitude displayed on the PFD regardless how busy it is. Perhaps rather then setting the final approach fix altitude of 9400 I could have just set 11000 instead but VNAV and approach mode at times help you to be ahead which is fine as long as all waypoints are verified and being monitored during the flight phase by both crew members.
Second reporter narrative
We were conducting the RNAV-A in VFR conditions to a very busy uncontrolled airport (HCR). We were assign a hold at 14000' at ZANGY intersection due a company aircraft ahead of us. After entering the hold we were cleared for the approach before completing one turn in holding. Once cleared for the approach the pilot flying selected the altitude alerter to 9400' for the final approach fix (UZEYU) and he selected VNAV AND APPR. He selected VS to attempt to catch the VPATH. Due to a busy environment neither of us remember if the VNAV properly captured. We noticed the aircraft descending below the required altitude of 11000'. By the time he used the CWS button to stop the descent we had descended to approximately 10500'. Before he could recover to 11000' ATC issued us a low altitude alert. He immediately recovered to 11000'In the future I plan to verify the VNAV PATH has captured and verify the magenta altitude next to the actual altitude on the PFD and try to stay more focused in the busy environment.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.