Narrative:

After takeoff, fll tower advised us of 'pop-up' VFR traffic at our 11 O'clock and 2 mi. We were climbing through 900 ft and our altitude was about 1500 ft when I spotted the traffic below us. When I notified the tower that I had a visual on the traffic, we were cleared to contact departure. At this time we reached and leveled off at 3000 ft, which was our assigned altitude. When I switched frequencys, departure was talking to another aircraft. After, the departure controller was finished, I checked in 'level 3000 ft.' the controller acknowledged our call sign and cleared us to turn to a '310 degree heading and maintain 13000 ft.' I read back both the heading and altitude and set the new altitude (13000 ft) in the altitude window on the panel. There was no reply from the controller. The first officer, who was flying the aircraft, and I used the 'double point' procedure to confirm the correct altitude was entered and armed. We began our climb and turn as instructed. Climbing through 4100 ft, the controller called us and stated 'call sign, you're assigned altitude was 3000 ft, maintain 4000 ft.' I replied, 'you assigned us 13000 ft, which I read back...we are now descending to 4000 ft.' he answered, 'I didn't assign 13000 ft...maintain 5000 ft.' we leveled at 5000 ft. The flight continued with no further incident nor loss of separation. Observation: during this high activity period of initial climb out, and with other distrs caused by VFR traffic, communications are very critical. There should be no references to altitudes unless they are different from what is being flown, especially if there is no time or requirement for a response or reply to a 'readback.'

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Original NASA ASRS Text

Title: FLC OF AN MD90 CLBED ABOVE AN INTERMEDIATE ASSIGNED ALT DURING INITIAL DEP DUE TO MISUNDERSTANDING OF THE CLRNC.

Narrative: AFTER TKOF, FLL TWR ADVISED US OF 'POP-UP' VFR TFC AT OUR 11 O'CLOCK AND 2 MI. WE WERE CLBING THROUGH 900 FT AND OUR ALT WAS ABOUT 1500 FT WHEN I SPOTTED THE TFC BELOW US. WHEN I NOTIFIED THE TWR THAT I HAD A VISUAL ON THE TFC, WE WERE CLRED TO CONTACT DEP. AT THIS TIME WE REACHED AND LEVELED OFF AT 3000 FT, WHICH WAS OUR ASSIGNED ALT. WHEN I SWITCHED FREQS, DEP WAS TALKING TO ANOTHER ACFT. AFTER, THE DEP CTLR WAS FINISHED, I CHKED IN 'LEVEL 3000 FT.' THE CTLR ACKNOWLEDGED OUR CALL SIGN AND CLRED US TO TURN TO A '310 DEG HDG AND MAINTAIN 13000 FT.' I READ BACK BOTH THE HDG AND ALT AND SET THE NEW ALT (13000 FT) IN THE ALT WINDOW ON THE PANEL. THERE WAS NO REPLY FROM THE CTLR. THE FO, WHO WAS FLYING THE ACFT, AND I USED THE 'DOUBLE POINT' PROC TO CONFIRM THE CORRECT ALT WAS ENTERED AND ARMED. WE BEGAN OUR CLB AND TURN AS INSTRUCTED. CLBING THROUGH 4100 FT, THE CTLR CALLED US AND STATED 'CALL SIGN, YOU'RE ASSIGNED ALT WAS 3000 FT, MAINTAIN 4000 FT.' I REPLIED, 'YOU ASSIGNED US 13000 FT, WHICH I READ BACK...WE ARE NOW DSNDING TO 4000 FT.' HE ANSWERED, 'I DIDN'T ASSIGN 13000 FT...MAINTAIN 5000 FT.' WE LEVELED AT 5000 FT. THE FLT CONTINUED WITH NO FURTHER INCIDENT NOR LOSS OF SEPARATION. OBSERVATION: DURING THIS HIGH ACTIVITY PERIOD OF INITIAL CLBOUT, AND WITH OTHER DISTRS CAUSED BY VFR TFC, COMS ARE VERY CRITICAL. THERE SHOULD BE NO REFS TO ALTS UNLESS THEY ARE DIFFERENT FROM WHAT IS BEING FLOWN, ESPECIALLY IF THERE IS NO TIME OR REQUIREMENT FOR A RESPONSE OR REPLY TO A 'READBACK.'

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.