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 (first officer); 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 first officer 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 first officer 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 first officer 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 first officer 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.

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Original NASA ASRS Text

Title: 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.

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.

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.