2024-05 · NASA ASRS report 2118913
Fractional flight crew reported an altitude deviation while on initial approach in mountainous terrain. ATC warned the crew of a low altitude alert; the crew climbed to the ATC assigned altitude and landed safely.
The flight departed from ZZZ for RIL at about XA:15 local time. As we were approaching RIL; the controller informed us that the approach had been NOTAM Closed just prior to our arrival. We proceeded to switch from the ILS to the RNAV approach to Runway 26. As we switched the controller gave us a decent to 14000 ft. We believed at the time that the controller said 10000 ft. As we descended through 12000 feet we noticed that we did not look to be at the proper altitude based upon the approach altitudes. Before we made our call to query ATC; the controller informed us of a low altitude alert and for us to climb to 13000 feet. That is when he issued us the deviation. Suggestions: For some context of the flight we were completing a 13 hour duty day during which we flew 8.4 hours of block time and the leg we received the deviation on was the fourth and final leg of the day. I think that the fatigue of a long duty and the high workload of switching of the approach contributed to the deviation. For a corrective action as a crew I believe we should mitigate our fatigue before it gets to that point and be more attentive during such a high work load situation.
Getting vectored towards RIL; Aspen approach informed us that the ILS 26 was out and asked if we can do an alternate approach. I selected the RNAV X 26 and informed Aspen approach. We re-briefed the new approach. Aspen approach gave us an altitude to descent to. I understood 10;000 ft. and I think I read back 10;000 ft. It was set in the altitude alerter and confirmed. Aspen cleared us direct to DOWNY. As we descended close to 12;000 ft. I noticed that DOWNY was depicted at 12200 ft. At this moment the controller gave us a low altitude alert and asked us to climb to 13;000 ft. and we did (VFR condition). Then the controller cleared us direct DOWNY. Then he cleared us for the ILS 26 and I told him it's the RNAV X 26 and he acknowledged that. We landed uneventful. The field was VFR. We never received a GPWS message or had a separation conflict. No other airplanes were around. The controller gave us an Aspens tower phone number to call after landing. I did.Suggestions: It was day 5 of our tour; 13 h duty; 8.4h flying. In MLB we had to correct the flight plan to ZZZ. It was filed right through a huge cluster of Thunderstorms reaching 50;000 ft. We had two early reports (wake up XA:30 am). The hotels were noisy and two really noise bad Hotels. The night at the new crew hotel in HPN was not good either. Our circadian rhythm was disturbed too. Two early reports (XB:00am); then XC:00 am; XE:00am; XD:30 am. I should have stopped in ZZZ and call fatigued.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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