Narrative:

Flying the canuk 7 arrival to atl; we were cleared to cross canuk intersection at 12000 ft. Altitude in the box and on the approach is 14000 ft. We changed it in the box to 12000 ft. 8 miles from canuk; approach changed our runway from runway 28 to runway 27L. Since the arrival is runway specific; we had to reload both the new ILS and also reload the canuk arrival. We were flying on LNAV and VNAV. While doing this; we had to 'dump' the arrival we were flying and reload the box. As we dropped in the arrival; the VNAV picked up the 14000 ft altitude (we had manually changed it once) at canuk and leveled off at 14000 ft. As we continued to load the arrival and then proceeded to 'clean it up' to canuk. By then we were past canuk so we had to 'clean it up' the next fix which was husky. We then noticed the aircraft had leveled off at 14000 ft instead of the 12000 ft we originally had set; so we hustled down to 12000 ft. Solution: ATC or approach needs to give us runway changes a lot earlier; or don't change them at all. They are asking us to dump the arrival that we already were on and reload another one. In the meantime; the aircraft keeps flying along straight or 'heading select' if selected because all waypoints have been dumped and all crossing restrictions previously entered have been dumped also. Callback conversation with reporter revealed the following information: reporter advised that; even though the STAR includes no specific runway assignment or associated runway transition; programming the STAR requires the selection of a runway prior to activation and any change of runway later assigned by ATC results in the FMC dropping out all STAR related lateral and vertical navigation data. Doing so necessitates that the entire procedure be reloaded and any route discontinuities or other chaff be closed and/or eliminated as appropriate. Reporter does not understand why it is necessary to make the runway selection part of the STAR programming inasmuch as all three arrival gates are simply waypoints from which the arrivals will be sequenced via radar vectors. He believes an unintended consequence of this programming protocol is the potential for the flight crew to forget to 'reprogram' the already altered crossing restriction that was previously manually reprogrammed due to an ATC amendment to the charted crossing altitude. Exactly what happened to them? He reiterated his suggestion that any runway change needs to be done early in the arrival or; better yet; the demand that a runway change require the entire STAR to be reloaded should be eliminated by making the three arrival gates independent STAR 'transitions' nonspecific to a particular runway.

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Original NASA ASRS Text

Title: A LATE CHANGE OF RWY WHILE FLYING THE CANUK RNAV STAR TO ATL CAUSES B757 FLT CREW TO RE-PROGRAM THE STAR IN ADDITION TO THE NEW RWY. DOING SO ELIMINATES MANUALLY ENTERED CLRNC TO CROSS CANUK AT 12000 FT VICE 14000 FT AS DISPLAYED BY THE DATABASE WHEN THE STAR IS LINE SELECTED.

Narrative: FLYING THE CANUK 7 ARR TO ATL; WE WERE CLEARED TO CROSS CANUK INTXN AT 12000 FT. ALT IN THE BOX AND ON THE APCH IS 14000 FT. WE CHANGED IT IN THE BOX TO 12000 FT. 8 MILES FROM CANUK; APCH CHANGED OUR RWY FROM RWY 28 TO RWY 27L. SINCE THE ARR IS RWY SPECIFIC; WE HAD TO RELOAD BOTH THE NEW ILS AND ALSO RELOAD THE CANUK ARR. WE WERE FLYING ON LNAV AND VNAV. WHILE DOING THIS; WE HAD TO 'DUMP' THE ARR WE WERE FLYING AND RELOAD THE BOX. AS WE DROPPED IN THE ARR; THE VNAV PICKED UP THE 14000 FT ALT (WE HAD MANUALLY CHANGED IT ONCE) AT CANUK AND LEVELED OFF AT 14000 FT. AS WE CONTINUED TO LOAD THE ARR AND THEN PROCEEDED TO 'CLEAN IT UP' TO CANUK. BY THEN WE WERE PAST CANUK SO WE HAD TO 'CLEAN IT UP' THE NEXT FIX WHICH WAS HUSKY. WE THEN NOTICED THE ACFT HAD LEVELED OFF AT 14000 FT INSTEAD OF THE 12000 FT WE ORIGINALLY HAD SET; SO WE HUSTLED DOWN TO 12000 FT. SOLUTION: ATC OR APCH NEEDS TO GIVE US RWY CHANGES A LOT EARLIER; OR DON'T CHANGE THEM AT ALL. THEY ARE ASKING US TO DUMP THE ARR THAT WE ALREADY WERE ON AND RELOAD ANOTHER ONE. IN THE MEANTIME; THE ACFT KEEPS FLYING ALONG STRAIGHT OR 'HDG SELECT' IF SELECTED BECAUSE ALL WAYPOINTS HAVE BEEN DUMPED AND ALL CROSSING RESTRICTIONS PREVIOUSLY ENTERED HAVE BEEN DUMPED ALSO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER ADVISED THAT; EVEN THOUGH THE STAR INCLUDES NO SPECIFIC RWY ASSIGNMENT OR ASSOCIATED RWY TRANSITION; PROGRAMMING THE STAR REQUIRES THE SELECTION OF A RWY PRIOR TO ACTIVATION AND ANY CHANGE OF RWY LATER ASSIGNED BY ATC RESULTS IN THE FMC DROPPING OUT ALL STAR RELATED LATERAL AND VERTICAL NAV DATA. DOING SO NECESSITATES THAT THE ENTIRE PROCEDURE BE RELOADED AND ANY ROUTE DISCONTINUITIES OR OTHER CHAFF BE CLOSED AND/OR ELIMINATED AS APPROPRIATE. REPORTER DOES NOT UNDERSTAND WHY IT IS NECESSARY TO MAKE THE RWY SELECTION PART OF THE STAR PROGRAMMING INASMUCH AS ALL THREE ARRIVAL GATES ARE SIMPLY WAYPOINTS FROM WHICH THE ARRIVALS WILL BE SEQUENCED VIA RADAR VECTORS. HE BELIEVES AN UNINTENDED CONSEQUENCE OF THIS PROGRAMMING PROTOCOL IS THE POTENTIAL FOR THE FLT CREW TO FORGET TO 'REPROGRAM' THE ALREADY ALTERED CROSSING RESTRICTION THAT WAS PREVIOUSLY MANUALLY REPROGRAMMED DUE TO AN ATC AMENDMENT TO THE CHARTED CROSSING ALT. EXACTLY WHAT HAPPENED TO THEM? HE REITERATED HIS SUGGESTION THAT ANY RWY CHANGE NEEDS TO BE DONE EARLY IN THE ARRIVAL OR; BETTER YET; THE DEMAND THAT A RWY CHANGE REQUIRE THE ENTIRE STAR TO BE RELOADED SHOULD BE ELIMINATED BY MAKING THE THREE ARRIVAL GATES INDEPENDENT STAR 'TRANSITIONS' NONSPECIFIC TO A PARTICULAR RWY.

Data retrieved from NASA's ASRS site as of May 2009 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.