Narrative:

Original arrival clearance was TTORO3. On climbout or cruise; we received a new arrival into iah; MSCOT4. I loaded this into the box; and based on the ATIS I loaded an ILS 26R approach into the FMS. Subsequently we were issued the drllr 5 arrival; and I believe we loaded the ILS 26R approach again. At some point on descent into iad on the DRLLR5; we were told to expect the RNAV rnp Y 26R approach. I loaded this into the box; set it up; did the QRH procedure 180.6; and based on the information we had (delayed into iah; long line of traffic on final showing on TCAS for 26R; etc. Etc.); I loaded the hooti transition into the FMS. Approx 5-10 miles prior to skler; we received an approach clearance for the RNAV rnp Y 26R. I don't recall who reloaded the box for the 4th or 5th time; but we needed to change the transition so that the airplane would fly the RF leg. When the approach was reloaded just prior to skler; there was a discontinuity built into the approach; and it reprogrammed the airplane to fly the 087 track after skler as per the drllr 5 arrival (although the RF leg was being depicted). We did not catch the fact that there were two sklers depicted in the box or that drkar was not the active waypoint (which it should have been with the RF leg); and so the airplane didn't immediately start the RF when we were expecting it to (although the RF leg was still depicted on the map. When I realized the airplane wasn't making the turn; I disconnected the autopilot and initiated the turn manually. As I started the turn; ATC told us to [contact] approach clearance; turn left to 090; and descend and maintain 3000 feet. We were vectored back out onto the approach on a long final and completed the RNAV rnp Y 26R approach without incident.

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Original NASA ASRS Text

Title: B737NG flight crew reported a track deviation occurred on the RNAV (RNP) Y approach to 26R in IAH when the flight crew failed to trap an FMC programming error.

Narrative: Original Arrival Clearance was TTORO3. On climbout or cruise; we received a new arrival into IAH; MSCOT4. I loaded this into the box; and based on the ATIS I loaded an ILS 26R approach into the FMS. Subsequently we were issued the DRLLR 5 Arrival; and I believe we loaded the ILS 26R approach again. At some point on descent into IAD on the DRLLR5; we were told to expect the RNAV RNP Y 26R approach. I loaded this into the box; set it up; did the QRH procedure 180.6; and based on the information we had (delayed into IAH; long line of traffic on final showing on TCAS for 26R; etc. etc.); I loaded the HOOTI transition into the FMS. Approx 5-10 miles prior to SKLER; we received an approach clearance for the RNAV RNP Y 26R. I don't recall who reloaded the box for the 4th or 5th time; but we needed to change the transition so that the airplane would fly the RF leg. When the approach was reloaded just prior to SKLER; there was a discontinuity built into the approach; and it reprogrammed the airplane to fly the 087 track after SKLER as per the DRLLR 5 arrival (although the RF leg was being depicted). We did not catch the fact that there were two SKLERs depicted in the box or that DRKAR was not the active waypoint (which it should have been with the RF leg); and so the airplane didn't immediately start the RF when we were expecting it to (although the RF leg was still depicted on the MAP. When I realized the airplane wasn't making the turn; I disconnected the autopilot and initiated the turn manually. As I started the turn; ATC told us to [contact] approach clearance; turn left to 090; and descend and maintain 3000 feet. We were vectored back out onto the approach on a long final and completed the RNAV RNP Y 26R Approach without incident.

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.