Date: 201603
Local time of day: 0601-1200
Location: D10.TRACON, TX
Flight conditions: VMC
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Mission: Passenger
Flight phase: Descent
Airspace: Class B D10
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Workload
Second reporter function: Pilot Flying; First Officer
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: Our original routing was to fly the DOOBI 2 arrival after AEX. Shortly after contacting Houston Center we were issued the SKNRD 4 arrival 8L transition. We had discussed this possible change; because the ATIS was showing an east runway for landing that the time; and were not surprised by the change.After crossing AEX we started to receive numerous delay vectors south of the arrival; as well as a number of speed reductions; and step down altitudes. All for spacing; as it was very busy with arrivals into IAH at the time.After we had received a final speed assignment of 250kts.; and a last delay vector we were cleared direct DOOBI to rejoin the arrival. As we approached DOOBI on an approximate 280 heading we were told to resume 'published speeds'; rejoin the SKNRD 4 arr. after DOOBI. As we were attempting to program the FMC for the correct speed (280KTS.) at DOOBI; and as we approached the DOOBI intersection (just 1 or 2 miles at most); is where it gets very confusing!As we crossed DOOBI we were issued a 'descent via' the arrival clearance; and told to now fly the SKNRD 4 arr. with a '8R' transition. The First Officer (FO); who was flying; selected the SKNRD 4 arrival/8R transition just as we crossed DOOBI Int. This caused a discontinuity in the route as the FMC rebuilt the entire arrival starting at AEX. The discontinuity dropped the autopilot into CWS mode; and we continued to fly on the 280 heading after DOOBI instead of turning to rejoin the arrival which would have been a 242 track to SKNRD int.My attention was focused on two things at this point. First we were now headed north of the arrival; and needed to quickly get the autopilot out of CWS; and back into a heading mode (which meant re-sequencing the legs page back from AEX to SKNRD); and second the FO was starting to get a little over whelmed. He was new [to the Company]; and [to] the 737 having just past the 100 hrs. in type during the first day of our 3 day trip (this was day 3) [and] was confused as to what to do.Up till this point the FO had done a great job; and I had full confidence in his abilities; but somehow; and I'm not exactly sure how; the wrong arrival got selected. Best I can figure is that because DOOBI was so prominent (the original arrival; and the intersection we had just crossed) that the DOOBI arrival got selected; and not the SKNRD.The FO asked me to confirm the change and with my attention mostly focused on getting turned back to the arrival; I agreed with the change; and it got executed. I knew we were now slightly north of the arrival track; so I thought I could help the FO get caught back up if I re-engage LNAV to rejoin the arrival. Once LNAV was back in the controlling mode; and out of CWS I felt I would have time to verify that the correct way points were loaded; and that we were headed for the 8R transition which I knew would take us south of the airport for a right downwind; not north of the field as would have been the case if landing on 8L.The only problem; and it was a big one; was that we were now flying towards HHART int. the next fix on the DOOBI 2 arrival; not SKNRD; which should have been our next fix.As we tracked towards HHART I was trying to find it; and the rest of the fixes for the SKNRD 4 to verify that we were caught up; but I was very confused; because I could not find it. The controller now was trying to confirm with us that we knew which transition we should be on; because he could see that we were not tracking towards SKNRD.It was at this point I realized our error. The controller just asked us to go direct KNGWD to rejoin the SKNRD arr. We now reprogrammed the FMC with the correct arrival (SKNRD) which caused yet another route discontinuity which we had to clean up; and got the airplane headed for KNGWD; and the correct sequence of fixes. Fortunately HHART and KNGWD both have 10;000 feet crossings so there was no altitude deviations relatively speaking. We continued uneventfully to landing on 8R once back on the correct arrival track.


Second narrative: Our original planed arrival into IAH was the DOOBI2 RNAV and that was programed and verified. During the early part of the flight the Pilot Monitoring (PM) pointed out that we will most likely get the SKNRD4 as IAH was landing east. Doing the later part of the flight we were assigned the SKNRD4 arrival and put in Runway 8L as that's what we had planned and briefed. During the descent before SKNRD we were vectored; slowed down; sped up and also assigned to a new runway of 8R which changed the entire arrival after KNGWD. As the flying pilot with the Autopilot (AP) on; I went into the box and entered the new runway; re-entered the arrival and starting point of the arrival of AEX. I asked the PM if AEX would cause an issue since we were already far past that point and he indicated that we needed to put in start and we could clean it up. I am new to the aircraft and complied. We both verified all the information on the FMC was entered correctly and then excited. I am a strong believer in Verbalize; Verify and Monitor and we both did that as the new assigned route was entered.After the execution and engagement of LNAV; we were now turning to what I thought was back on route with the arrival. ATC quickly notified us that it appears we were off course and not going to KNGWD. That was indeed true and we were somehow going to HHART which is on the DOOBI2 Arrival. Thanks to ATC's quick and accurate detection of our error; we were back on course in under a minute with vectors causing our lateral error to be 2 miles or less at best guess.There was a lot happening fast during this phase of flight and being a new to the aircraft; I can only surmise that I entered the wrong arrival believing I was entering the correct one. The part that is most troubling is that we both looked pointed and confirmed the runway and arrival before executing the route. There is no doubt that my being new to the aircraft was a threat which was briefed on every leg and an added work load for the PM.


Synopsis: B737 flight crew reported a track deviation resulted when the relatively inexperienced First Officer made an error programming the FMC and the Captain failed to catch it.