Narrative:

Flight from mci to ewr. On climb out of mci, while cleared to 15000 ft, I did not hear the first officer as he received the clearance to what he thought was FL330. As we climbed through FL230, the controller said maintain FL230. I immediately descended back to FL230, the controller then asked if we were assigned a different altitude as she had just come on the scope. We told her that we believed that we were cleared to FL330. We asked if there was a problem and she said that they would have to listen to the tapes. After landing at ewr, I called the center and they said that the tapes were very scratchy but they believed that we read back FL230. They verified that there was no loss of separation but by this time the report had been filed. During this time frame, 18000 ft to FL230, a flight attendant came to the flight deck to take drink orders, which is customary. This could have contributed to the problem. So now I don't turn off the sterile flight deck light until we have been cleared above FL230 and have received the cruise altitude clearance. Also, every altitude clearance is now verbally repeated by both pilots. Supplemental information from acn 277098: something else I noticed on the advanced 737's, is that the mode control panel, which has heading, course, and altitude information is done with a gray liquid crystal display on a black backgnd, which is extremely difficult to see on a sunny day.

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Original NASA ASRS Text

Title: ALTDEV DURING CLBOUT.

Narrative: FLT FROM MCI TO EWR. ON CLBOUT OF MCI, WHILE CLRED TO 15000 FT, I DID NOT HEAR THE FO AS HE RECEIVED THE CLRNC TO WHAT HE THOUGHT WAS FL330. AS WE CLBED THROUGH FL230, THE CTLR SAID MAINTAIN FL230. I IMMEDIATELY DSNDED BACK TO FL230, THE CTLR THEN ASKED IF WE WERE ASSIGNED A DIFFERENT ALT AS SHE HAD JUST COME ON THE SCOPE. WE TOLD HER THAT WE BELIEVED THAT WE WERE CLRED TO FL330. WE ASKED IF THERE WAS A PROB AND SHE SAID THAT THEY WOULD HAVE TO LISTEN TO THE TAPES. AFTER LNDG AT EWR, I CALLED THE CTR AND THEY SAID THAT THE TAPES WERE VERY SCRATCHY BUT THEY BELIEVED THAT WE READ BACK FL230. THEY VERIFIED THAT THERE WAS NO LOSS OF SEPARATION BUT BY THIS TIME THE RPT HAD BEEN FILED. DURING THIS TIME FRAME, 18000 FT TO FL230, A FLT ATTENDANT CAME TO THE FLT DECK TO TAKE DRINK ORDERS, WHICH IS CUSTOMARY. THIS COULD HAVE CONTRIBUTED TO THE PROB. SO NOW I DON'T TURN OFF THE STERILE FLT DECK LIGHT UNTIL WE HAVE BEEN CLRED ABOVE FL230 AND HAVE RECEIVED THE CRUISE ALT CLRNC. ALSO, EVERY ALT CLRNC IS NOW VERBALLY REPEATED BY BOTH PLTS. SUPPLEMENTAL INFO FROM ACN 277098: SOMETHING ELSE I NOTICED ON THE ADVANCED 737'S, IS THAT THE MODE CTL PANEL, WHICH HAS HDG, COURSE, AND ALT INFO IS DONE WITH A GRAY LIQUID CRYSTAL DISPLAY ON A BLACK BACKGND, WHICH IS EXTREMELY DIFFICULT TO SEE ON A SUNNY DAY.

Data retrieved from NASA's ASRS site as of July 2007 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.