Air Taxi flight crew reported a descent deviation while executing the WAYVE1 arrival into LAX; which resulted in a terrain alert being issued by Air Traffic Control.
Synopsis
Air Taxi flight crew reported a descent deviation while executing the WAYVE1 arrival into LAX; which resulted in a terrain alert being issued by Air Traffic Control.
Narrative
During the descent phase to LAX; I was assigned the SADDE8 arrival to LAX. Then I was assigned the WAYVE1 arrival; direct to fix PAIDD. Passing PAIDD; ATC advised to expect 7;000 south of Lake Hughes (LHS). Cross checking the STAR; the fix WAYVE (LHS142/007) has an MEA of 7;000 outbound. I was then given the assignment to cross 7 miles south of Lake Hughes at eleven thousand. While read back correctly; I must have selected seven thousand in the Altitude pre-select; confusing 'Seven' with 'Eleven'. The radios were very busy and this assignment created a steep descent angle in a very short amount of time as I crossed LHS at approximately 12;300. I am familiar with the LHS area and I know I was safe from terrain and I could see outside the windows I was safe. Being a busy area; I was also focused on traffic that might be in the area (TCAS) and looking outside.Passing about 9;000 MSL; I got the call from LA center to level off immediately and was given the terrain alert. Subsequent calls to watch supervisor indicated I was 300 feet below MVA. I leveled off immediately and returned to assigned altitude. No near miss; evasive action or other conflicts occurred or were reported.Factors and perceptions: high workload area; processing what I expected to hear 'Seven' instead of what was actually said 'eleven'; reading the STAR chart with '7;000' printed at WAYVE produced a confirmation bias; trying to meet the assigned altitude of 'seven' thousand in a very short amount of time of 1-1.5 minutes while maintaining situational awareness of the terrain and traffic; very busy radios; many changes to the assigned routing requiring flexibility to adapt to new STARs.
Second reporter narrative
Busy ATC environment; high cockpit workload; STAR Change. Descent into LAX. ATC assigned crossing restriction 7 NM south of fix at 11;000. WE erred and set 7;000 in MCP panel. ATC called us and we climbed back up to proper altitude. They gave us phone number to call on landing in LAX.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.