Date: 201909
Local time of day: 0601-1200
Location: PHX.Tower, AZ
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B PHX
ATC / advisory: Tower PHX
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: First Officer was pilot flying. Initially cleared final for Runway 25L. Offered Runway 25R. This is a longer runway and therefore a better option for any aircraft if offered. Runway 25L and Runway 25R have significantly different threshold locations; and Runway 25R has no VASI. First Officer stated he had airport in sight and acknowledged that the assigned runway was 25R. I told the First Officer that I would change the runway for him and remove the glide slope that was currently displayed as this would be disorienting. Our intercept angle for localizer to Runway 25L was very shallow and I felt I could easily change Runways in FMC and establish an artificial glide slope. I went heads down outside the FAF for what I perceived was a reasonable length of time based on the intercept angle. I had left the speaker on for our jumpseat rider so he could follow along; but cannot attest to its effectiveness as I was wearing a noise canceling headset. The first time I was aware of the deviation was when Tower called. My impression is we must have turned somewhat right; otherwise we would have intercepted the extended centerline for Runway 26 closer to the airport than we were. I told the First Officer that he was lined up on Runway 26 as opposed to Runway 25R. I further pointed out the TCAS depiction of the traffic very close to our flight path and only 100 ft. above us. I can't explain why the TCAS presentation was not sufficiently scary; it scared me when I looked at it.Our heading to Runway 25L would have intercepted final outside the marker and therefore our heading would have been perfect for Runway 25R. Don't know how we ended up where we did as far out on the final for Runway 26; especially considering the TCAS display. While I feel comfortable flying without lots of electronic cross checks; most of the people I fly with now like this stuff as it is very useful. I believe that even though he acknowledged Runway 25; the First Officer must have been thinking Runway 26. I have flown with the pilot a few times and believe he is competent and at a loss for how he got there particularly in light of the TCAS presentation. I don't know if the jumpseat rider was aware of what was going on when I went heads down. The First Officer is a great guy; but is very difficult to understand given [language] is his first language. I don't believe this was a factor during this encounter; but has proved at times time consuming. It may well be that I am difficult for him to understand at times.While there was a little sun; all runways were in plain sight. I could have refused the longer runway and not established an artificial glide path for the First Officer; but had one of several other possible scenarios occurred; I would be faulted for not taking the action that I took. I really feel strongly that the incorporated software in the B737 is far inferior to that which was incorporated in the next generation of aircraft that are no longer produced for passenger use. This software requires too much heads down time and always presents the user with the task of getting the aircraft to quickly do what you want it to do rather than quizzing you why it won't let you do what you want. I routinely jumpseat on other 737 operators and they all say the same thing. There is user friendly software out there. If someone tells me they have the runway in sight as I do and acknowledge the runway assignment; I am not sure how best to proceed. I really thought he was looking at the correct runway when I went heads down. I have been flying for about 44 years and have never had anything like this happen. I like single seat better; at least I know what I don't know. It's hard to know what another doesn't know. Mark Twain said it best; 'it's not what you think you know; but what you think you know that ain't so' that gets you.'




Synopsis: B737-800 Captain reported that the First Officer misinterpreted the runway assignment on approach; resulting in a track deviation.