Corporate flight crew reported an assigned altitude excursion during initial approach which resulted in a EGPWS 'Terrain' alert. Flight crew immediately climb back to assigned altitude and completed a safe landing.
Synopsis
Corporate flight crew reported an assigned altitude excursion during initial approach which resulted in a EGPWS 'Terrain' alert. Flight crew immediately climb back to assigned altitude and completed a safe landing.
Narrative
While being radar vectored by ZZZ Approach; during descent; an intermediate altitude of 13000 ft. was assigned. During a period of cockpit saturation in IMC; 12000 ft. was selected in the altitude pre-select. The pilot not flying (PNF) occupying the right hand seat called 12000 set and the pilot flying (PF) in the left hand seat confirmed 12000 ft. Both pilots were convinced that the assigned altitude was 12000 ft. The airplane being flown with the Autopilot engaged consequently did not level off at 13000 ft. as instructed by ATC. At approximately 12500 ft.; ATC advised the crew of the altitude excursion and immediately instructed crew to climb to 13000 as assigned. Concurrent with the ATC intervention; the crew received an aural caution annunciation of ' Caution: Terrain'. Synonymous with ATC intervention and alerting of the EGPWS system; crew immediately climbed back to 13000.Radar vectoring continued until aircraft was established on the LOC DME approach for Runway XX at ZZZ. Approach and landing conducted normally.
Second reporter narrative
While being vectored for approach; received ATC clearance to descend to 13000. Altitude window was set at 12000 and confirmed by both pilots per company sop. Pilot flying (PF) thought he heard 12000; confirmed 12000 with pilot monitoring (PM) and continued descent below 13000. At approximately 12500 received a caution terrain EGPWS alert while simultaneously getting a call from ATC; low altitude alert; climb to 13000. PF immediately took corrective action and climbed to 13000.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.