Narrative:

As the first officer; I was the pilot monitoring on this flight. This was the second flight of the first day flying with this captain; whom I've never met before. Heading direct to pmd VOR on the lynxx 8 arrival; socal approach told us to descend to 8000 ft 10 miles northeast of janny intersection (the point after pmd on our flight plan). We were at 13;000 ft. The captain set 8000 ft in the altitude selector window; looked at the legs page; and made no changes to the flight plan. I asked him if he was going to make a new point and add in the new altitude; which we do regularly. He replied it would work because the point prior has an altitude. I told him it would not work; and he has to make an input to the flight plan to make the 8000 ft restriction. He talked more about his logic and was able to convince himself the flight plan did not need to be altered. I considered my options at that point. On my third and final attempt; I said; 'okay; but it's not going to work the way you have it in right now; and you will need to hand fly it; if you're going to make the altitude by the required point.' he said it will work and made no changes. We were silent for a while and then very late he realized it wasn't going to work. He used a steep vertical speed; taking us to about 285 knots below 10;000 ft. We simultaneously received a call from ATC to increase our rate of descent and that there was traffic below us that we were approaching. I told ATC we were increasing our descent. ATC gave us a vector for traffic avoidance. We received a TCAS TA and made visual contact with the traffic. The rest of the flight was uneventful.

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Original NASA ASRS Text

Title: After receiving a crossing restriction 10 NM prior to a point on the STAR; the non-flying FO was unable to convince the Captain to add a new fix to the FMC Legs Page to represent the point where ATC had cleared them to cross at 8;000 feet. As a result the crossing restriction was not met and an airborne conflict resulted which necessitated an ATC vector.

Narrative: As the First Officer; I was the Pilot Monitoring on this flight. This was the second flight of the first day flying with this Captain; whom I've never met before. Heading direct to PMD VOR on the LYNXX 8 Arrival; SoCal Approach told us to descend to 8000 ft 10 miles northeast of JANNY intersection (the point after PMD on our flight plan). We were at 13;000 ft. The Captain set 8000 ft in the altitude selector window; looked at the LEGS page; and made no changes to the flight plan. I asked him if he was going to make a new point and add in the new altitude; which we do regularly. He replied it would work because the point prior has an altitude. I told him it would not work; and he has to make an input to the flight plan to make the 8000 ft restriction. He talked more about his logic and was able to convince himself the flight plan did not need to be altered. I considered my options at that point. On my third and final attempt; I said; 'Okay; but it's not going to work the way you have it in right now; and you will need to hand fly it; if you're going to make the altitude by the required point.' He said it will work and made no changes. We were silent for a while and then very late he realized it wasn't going to work. He used a steep vertical speed; taking us to about 285 knots below 10;000 ft. We simultaneously received a call from ATC to increase our rate of descent and that there was traffic below us that we were approaching. I told ATC we were increasing our descent. ATC gave us a vector for traffic avoidance. We received a TCAS TA and made visual contact with the traffic. The rest of the flight was uneventful.

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.