2022-04 · NASA ASRS report 1890697
Air carrier Pilots reported thinking they were cleared for the approach and descended early.
On the SAMMR3 Arrival ATC told us to expect the RNAV Z 26L. We requested RNAV Y 26L since we had already set up and reviewed it. ATC told us to expect that. Cleared us direct to BUSEY and descend to 8;000. The Captain and I thought we had been cleared for the approach and the Captain activated approach mode. We were already in the descent from cruise flight. Since we were in APR mode the aircraft descend on the APR path through 8;000 feet. About 5 miles from BUSEY ATC issued a low altitude alert and to check our altitude because we had descended below the MVA for the area. We were at approximately 7;200 feet. 800 below the assigned 8;000. We initiated a climb but were given a clearance to descend to 6;900 at BUSEY and cleared for the approach. Continued the approach and landed. Last leg of the day at night. Did not realize we had not been cleared for the approach; and that we were not yet on a published segment of the approach. Also conditions were VFR so we could have flown a visual. I think this lead to some complacency on my part. Also relatively new Captain and First officer. Verify that approach clearance was given before entering APR mode on FGC.
Just outside SAMMR intersection we checked in with approach control. They cleared us to descend to 8;000' and to proceed direct to BUSEY (IF 6;900') for the RNAV Y to 26L. I mistakenly thought we were cleared for the approach and armed the approach mode after I started the descent. The controller questioned us as we we descended through approximately 7;500'. I immediately leveled off and started a climb back to 8;000'; we were only a couple of miles from BUSEY at this point and the controller then cleared us for the approach and we landed uneventfully. We misunderstood the clearance; which caused us to start down early on the approach. Be absolutely certain of the clearance given; and question the controller if there is any uncertainty.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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