Air carrier flight crew reported pilot deviation. When the clearance for lower was issued by ATC; pilots both incorrectly heard; and pilot monitoring read back incorrect altitude.
Synopsis
Air carrier flight crew reported pilot deviation. When the clearance for lower was issued by ATC; pilots both incorrectly heard; and pilot monitoring read back incorrect altitude.
Narrative
During vectored descent inbound to destination airport; ATC issued a descend clearance to a lower altitude. Pilot Monitoring read back incorrect altitude which varied by 500 ft. lower. No confirmation from ATC was issued clarifying erroneous readback. Aircraft descended to incorrect altitude; resulting in loss with MVA/Terrain. After successful approach and landing; the flight crew was notified of possible pilot deviation when taxiing to the gate. Call was initiated after deplaning; with the pilots being only then alerted that it was a possible altitude deviation on descent/approach.Event happened during a busy time in the airspace; with much radio congestion. ATC Controller was very busy assigning headings; altitudes; speeds; and approach clearances to multiple aircraft. Pilots were busy dealing with turbulent conditions and adverse weather conditions within the vicinity of the descent. Slowing the aircraft and configuring while maintaining the descents given by ATC become a consuming task. When the clearance for lower was issued by ATC; pilots both incorrectly heard and pilot monitoring read back incorrect altitude.The flight crew could have requested further clarification regarding the altitude they believed they were assigned. ATC could have verified pilots received proper interpretation of clearance. Improvements in communication could have been made on both the sender's and receiver's side.
Second reporter narrative
We were being vectored on downwind for a visual approach to Runway 34L into SLC by approach. I was the Pilot Flying and the First Officer was pilot monitoring. We were given a descent to 8500; but the monitoring pilot heard 8000 and read back descend to 8000". We were not corrected by ATC for reading back the wrong altitude. I dialed in 8000 and we both confirmed 8000. I descended to 8000. We continued to be vectored to land. We landed and upon switching to ground control we were given a phone number to call for a possible pilot deviation. We taxied to the gate with no other incidents. The cause of this event was poor communication between ATC and both Pilots. This is also an area of high vulnerability between the Pilot Flying (PF) and the Pilot Monitoring; with the PF calling for configuration changes to the aircraft and the Pilot Monitoring applying those configurations and also taking radio calls from ATC. I suggest that pilots write down their altitude instructions or use the scratch pad when given altitude or heading changes from ATC."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.