Narrative:

While on a flight to smo the weather at smo required a divert to vny. On approach into the vny area the approach controller cleared us to intercept the localizer for the ILS Z 16R at vny. We were already flying through the course. We corrected the course and we were told to descend to 3000 then he came back and said to maintain 5500 for traffic. We set 5500 in the altitude selector and began looking for the traffic. We called the airport in sight; and the traffic about the same time he said to descend to 5000. The approach controller cleared us for the visual approach. He then came back and said maintain 5000. When he cleared us for the approach the pilot flying activated the appr mode. We were both looking for the traffic because the traffic had initiated a turn back towards us. The aircraft intercepted the glideslope and continued descending through 5000 ft to about 4700 ft when the pilot realized the aircraft was still descending. The pilot flying disengaged the autopilot and returned the aircraft to the assigned altitude of 5000 ft. About the same time the TCAS sounded off with a RA to climb and ATC called traffic again. We told him we still had the traffic in sight. The other aircraft was passing off the right side below us at about 3 miles. ATC told us to delete the altitude restriction and contact the tower. We did and landed safely.the confusing clearance of cleared for the visual and then giving an altitude restriction combined with multiple traffic to see and avoid and poor visibility with the sunset created a heavy workload environment and the pilot flying neglected to change the automation from appr to navigation modes. Both pilots were tired and there was confusion over clearance phraseology. Quickly correcting the navigation after the late turn from the arrival to the approach course coupled with multiple headings and altitude changes in a very short time plus quite a few aircraft to locate on the TCAS was a busy flight deck. A long day made us a little slower to respond and react than typical.it had been a very long day. This was the end of the day and occurred after a divert into vny had been initiated. We had been flying over 9 hours and were approaching our 14th hour of duty. Flying into the sun all day both eastbound and then westbound trips took its toll. We were tired. ATC was confusing. VFR traffic was abundant and not talking to ATC. Everyone has to fly through the same pass to get into or out of the vny area. It's not uncommon to have multiple VFR traffic flying through approach altitudes which disrupts normal operations for IFR traffic. I think had we not been on such a long day we would have responded quicker; been more attentive and not missed the automation error.

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Original NASA ASRS Text

Title: A Fractional flight crew flying the VNY Runway 16R ILS reported taking evasive action from VFR traffic as they began their descent at 5;000 feet. The crew cited fatigue as a factor.

Narrative: While on a flight to SMO the weather at SMO required a divert to VNY. On approach into the VNY area the approach controller cleared us to intercept the localizer for the ILS Z 16R at VNY. We were already flying through the course. We corrected the course and we were told to descend to 3000 then he came back and said to maintain 5500 for traffic. We set 5500 in the altitude selector and began looking for the traffic. We called the airport in sight; and the traffic about the same time he said to descend to 5000. The approach controller cleared us for the visual approach. He then came back and said maintain 5000. When he cleared us for the approach the pilot flying activated the APPR mode. We were both looking for the traffic because the traffic had initiated a turn back towards us. The aircraft intercepted the glideslope and continued descending through 5000 ft to about 4700 ft when the pilot realized the aircraft was still descending. The pilot flying disengaged the autopilot and returned the aircraft to the assigned altitude of 5000 ft. About the same time the TCAS sounded off with a RA to climb and ATC called traffic again. We told him we still had the traffic in sight. The other aircraft was passing off the right side below us at about 3 miles. ATC told us to delete the altitude restriction and contact the tower. We did and landed safely.The confusing clearance of cleared for the visual and then giving an altitude restriction combined with multiple traffic to see and avoid and poor visibility with the sunset created a heavy workload environment and the pilot flying neglected to change the automation from APPR to NAV modes. Both pilots were tired and there was confusion over clearance phraseology. Quickly correcting the navigation after the late turn from the arrival to the approach course coupled with multiple headings and altitude changes in a very short time plus quite a few aircraft to locate on the TCAS was a busy flight deck. A long day made us a little slower to respond and react than typical.It had been a very long day. This was the end of the day and occurred after a divert into VNY had been initiated. We had been flying over 9 hours and were approaching our 14th hour of duty. Flying into the sun all day both eastbound and then westbound trips took its toll. We were tired. ATC was confusing. VFR traffic was abundant and not talking to ATC. Everyone has to fly through the same pass to get into or out of the VNY area. It's not uncommon to have multiple VFR traffic flying through approach altitudes which disrupts normal operations for IFR traffic. I think had we not been on such a long day we would have responded quicker; been more attentive and not missed the automation error.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.