Narrative:

During climb out from atl on the pnut 3 RNAV departure; we were assigned 13000 ft at our altitude. We were level at 13000 ft when the controller called out traffic at 3 mi out and 1000 ft above us. We could not see the traffic. Soon we did acquire the traffic visually and reported this to the controller. The controller responded 'maintain visual separation with the traffic -- 14000 ft -- contact ZTL on 134.5.' the transmission was garbled and the first officer; the PF; thought the transmission was a clearance to climb to 14000 ft. As the captain checked in with the next controller; I (the first officer) began a climb to 14000 ft. The captain asked 'why are we climbing.' at this point; I realized that I may have misunderstood the clearance but was already passing 13400 ft. The new controller hesitated to answer us and asked us 'did the previous controller give you that?' in reference to the altitude. The captain and I then discussed what the previous controller said and we were both unsure of what exactly it was. The traffic at 14000 ft was moving away from us and did not create a conflict. The new controller seemed confused as to what our previous clearance was but immediately cleared us to continue our climb to FL220. We continued on the route.

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Original NASA ASRS Text

Title: MD88 DEPARTS CRUISE ALT BASED ON CLRNC HEARBACK CLRNC READBACK ERROR. LOSS OF SEPARATION WITH SECOND MD88 RESULTS.

Narrative: DURING CLBOUT FROM ATL ON THE PNUT 3 RNAV DEP; WE WERE ASSIGNED 13000 FT AT OUR ALT. WE WERE LEVEL AT 13000 FT WHEN THE CTLR CALLED OUT TFC AT 3 MI OUT AND 1000 FT ABOVE US. WE COULD NOT SEE THE TFC. SOON WE DID ACQUIRE THE TFC VISUALLY AND RPTED THIS TO THE CTLR. THE CTLR RESPONDED 'MAINTAIN VISUAL SEPARATION WITH THE TFC -- 14000 FT -- CONTACT ZTL ON 134.5.' THE XMISSION WAS GARBLED AND THE FO; THE PF; THOUGHT THE XMISSION WAS A CLRNC TO CLB TO 14000 FT. AS THE CAPT CHKED IN WITH THE NEXT CTLR; I (THE FO) BEGAN A CLB TO 14000 FT. THE CAPT ASKED 'WHY ARE WE CLBING.' AT THIS POINT; I REALIZED THAT I MAY HAVE MISUNDERSTOOD THE CLRNC BUT WAS ALREADY PASSING 13400 FT. THE NEW CTLR HESITATED TO ANSWER US AND ASKED US 'DID THE PREVIOUS CTLR GIVE YOU THAT?' IN REF TO THE ALT. THE CAPT AND I THEN DISCUSSED WHAT THE PREVIOUS CTLR SAID AND WE WERE BOTH UNSURE OF WHAT EXACTLY IT WAS. THE TFC AT 14000 FT WAS MOVING AWAY FROM US AND DID NOT CREATE A CONFLICT. THE NEW CTLR SEEMED CONFUSED AS TO WHAT OUR PREVIOUS CLRNC WAS BUT IMMEDIATELY CLRED US TO CONTINUE OUR CLB TO FL220. WE CONTINUED ON THE RTE.

Data retrieved from NASA's ASRS site as of January 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.