Narrative:

On the kooly arrival into phx at FL340; ZAB cleared us direct to itemm and cross itemm at FL250 and also to hold at itemm as published. An hour before; we were given holding en route to a fix north of zun for the eagle arrival into phx; and had some initial programming difficulties getting the FMC to initiate a present position (ppos) hold. After getting the FMC properly programmed; we held at the ppos (approximately 180 mi west of zun) as directed. When we were given the change in arrival (assigned arrival was changed 3 times due to the rapidly changing thunderstorms near phx and ATC congestion) and the holding at itemm; we began to set up the holding and realized at the same time as the aircraft ahead of us that there was no published holding at itemm. Once we clarified with abq the specific holding instructions (hold east of itemm on the 90 degree radial; right hand turns; 10 mi legs) we began to program the FMC. As the pm; I wrote down the altitude assigned along with the holding instructions; but did not immediately set FL250 in the altitude window and did not update/change the standard altitude of FL240 for itemm in the FMC legs page since we were busy with setting up the FMC holding at itemm; reviewing our diversion plan with each other and with dispatch via ACARS (diversion planning partially complicated due to #1 fuel tank indicator that was intermittent -- sometimes read zero and sometimes read correctly); and lastly keeping the flight attendants and the passenger informed/updated on the arrival time situation. As we approached within 25 mi of itemm; as the pm; I told the captain as the PF that we needed to start descending soon to meet the crossing restr at itemm which I then set at FL240 looking at the FMC legs page instead of my written clearance of FL250 assigned. As the captain descended below FL250 he noticed on the TCAS that we were approaching the same altitude as the aircraft ahead of us and then realized that we had set the wrong altitude in the autoplt altitude select window. Just as the captain arrested our descent (approximately at 24300 ft MSL) and began to climb toward FL250; ZAB queried us about our altitude. We informed abq that we were correcting our altitude. Crews need to be vigilant at clarifying clrncs with each other and ATC and then immediately setting up the clearance on their instruments/displays. Once rtes and altitudes are set up; then the holding can be programmed into the FMC and then other tasks (diversion planning; updating flight attendants and passenger; etc) can be performed. Any delay in setting up the route or altitude clearance can lead to mistakes. Company procedures are designed to prevent mistakes by emphasizing the setting of the altitude or route clearance immediately after receiving the clearance and then confirming the setting. Crews need to be vigilant that other tasks or distrs do not disrupt the normal procedural habits.

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Original NASA ASRS Text

Title: B737 ON APCH TO PHX EXPERIENCES EXCURSION FROM ASSIGNED ALTITUDE AFTER CONFUSION BETWEEN WRITTEN CLEARANCE AND 'LEGS' PAGE.

Narrative: ON THE KOOLY ARR INTO PHX AT FL340; ZAB CLRED US DIRECT TO ITEMM AND CROSS ITEMM AT FL250 AND ALSO TO HOLD AT ITEMM AS PUBLISHED. AN HR BEFORE; WE WERE GIVEN HOLDING ENRTE TO A FIX N OF ZUN FOR THE EAGLE ARR INTO PHX; AND HAD SOME INITIAL PROGRAMMING DIFFICULTIES GETTING THE FMC TO INITIATE A PRESENT POS (PPOS) HOLD. AFTER GETTING THE FMC PROPERLY PROGRAMMED; WE HELD AT THE PPOS (APPROX 180 MI W OF ZUN) AS DIRECTED. WHEN WE WERE GIVEN THE CHANGE IN ARR (ASSIGNED ARR WAS CHANGED 3 TIMES DUE TO THE RAPIDLY CHANGING TSTMS NEAR PHX AND ATC CONGESTION) AND THE HOLDING AT ITEMM; WE BEGAN TO SET UP THE HOLDING AND REALIZED AT THE SAME TIME AS THE ACFT AHEAD OF US THAT THERE WAS NO PUBLISHED HOLDING AT ITEMM. ONCE WE CLARIFIED WITH ABQ THE SPECIFIC HOLDING INSTRUCTIONS (HOLD E OF ITEMM ON THE 90 DEG RADIAL; R HAND TURNS; 10 MI LEGS) WE BEGAN TO PROGRAM THE FMC. AS THE PM; I WROTE DOWN THE ALT ASSIGNED ALONG WITH THE HOLDING INSTRUCTIONS; BUT DID NOT IMMEDIATELY SET FL250 IN THE ALT WINDOW AND DID NOT UPDATE/CHANGE THE STANDARD ALT OF FL240 FOR ITEMM IN THE FMC LEGS PAGE SINCE WE WERE BUSY WITH SETTING UP THE FMC HOLDING AT ITEMM; REVIEWING OUR DIVERSION PLAN WITH EACH OTHER AND WITH DISPATCH VIA ACARS (DIVERSION PLANNING PARTIALLY COMPLICATED DUE TO #1 FUEL TANK INDICATOR THAT WAS INTERMITTENT -- SOMETIMES READ ZERO AND SOMETIMES READ CORRECTLY); AND LASTLY KEEPING THE FLT ATTENDANTS AND THE PAX INFORMED/UPDATED ON THE ARR TIME SIT. AS WE APCHED WITHIN 25 MI OF ITEMM; AS THE PM; I TOLD THE CAPT AS THE PF THAT WE NEEDED TO START DSNDING SOON TO MEET THE XING RESTR AT ITEMM WHICH I THEN SET AT FL240 LOOKING AT THE FMC LEGS PAGE INSTEAD OF MY WRITTEN CLRNC OF FL250 ASSIGNED. AS THE CAPT DSNDED BELOW FL250 HE NOTICED ON THE TCAS THAT WE WERE APCHING THE SAME ALT AS THE ACFT AHEAD OF US AND THEN REALIZED THAT WE HAD SET THE WRONG ALT IN THE AUTOPLT ALT SELECT WINDOW. JUST AS THE CAPT ARRESTED OUR DSCNT (APPROX AT 24300 FT MSL) AND BEGAN TO CLB TOWARD FL250; ZAB QUERIED US ABOUT OUR ALT. WE INFORMED ABQ THAT WE WERE CORRECTING OUR ALT. CREWS NEED TO BE VIGILANT AT CLARIFYING CLRNCS WITH EACH OTHER AND ATC AND THEN IMMEDIATELY SETTING UP THE CLRNC ON THEIR INSTS/DISPLAYS. ONCE RTES AND ALTS ARE SET UP; THEN THE HOLDING CAN BE PROGRAMMED INTO THE FMC AND THEN OTHER TASKS (DIVERSION PLANNING; UPDATING FLT ATTENDANTS AND PAX; ETC) CAN BE PERFORMED. ANY DELAY IN SETTING UP THE RTE OR ALT CLRNC CAN LEAD TO MISTAKES. COMPANY PROCS ARE DESIGNED TO PREVENT MISTAKES BY EMPHASIZING THE SETTING OF THE ALT OR RTE CLRNC IMMEDIATELY AFTER RECEIVING THE CLRNC AND THEN CONFIRMING THE SETTING. CREWS NEED TO BE VIGILANT THAT OTHER TASKS OR DISTRS DO NOT DISRUPT THE NORMAL PROCEDURAL HABITS.

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.