Narrative:

Deviation from clearance altitude. Level at 17000 ft MSL, en route to eliot intersection we received a radio call from center to turn to '310.' first officer read back the heading in his soft spoken manner. However I thought the controller gave us a climb clearance to FL310. I repeated FL310 to the first officer and changed the altitude myself. I thought for sure he had pointed at the '310' in the window I had set. I started a slow climb initially and at 17800 ft MSL the controller corrected us to descend to 17000 ft MSL. There were no traffic conflicts according to the controller. IMC conditions and a busy scratchy radio contributed to the confusion. Supplemental information from acn 631173: I received a clearance from ATC to 'turn right heading 310 vectors for climb.' I then looked at my SID plate to see if anything else applied to our departure. As I looked back to the instrument panel I noticed we were climbing and '310' was set in the altitude window and we did not turn from our original heading. As I was asking the captain if he set that altitude in the window, thinking I missed something here, ATC called and asked our altitude, I said 17600 ft. She said to go back to 17000 ft, which we did. She then asked what altitude we were climbing to and I said FL310. Then she said that was a heading of 310 degrees not an altitude and sent us directly to eliot. The controller said we did not cause any problems.

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Original NASA ASRS Text

Title: MD80 CREW BEGAN A CLB TO FL310 WHEN THEY WERE CLRED TO HDG 310 DEGS.

Narrative: DEV FROM CLRNC ALT. LEVEL AT 17000 FT MSL, ENRTE TO ELIOT INTXN WE RECEIVED A RADIO CALL FROM CTR TO TURN TO '310.' FO READ BACK THE HDG IN HIS SOFT SPOKEN MANNER. HOWEVER I THOUGHT THE CTLR GAVE US A CLB CLRNC TO FL310. I REPEATED FL310 TO THE FO AND CHANGED THE ALT MYSELF. I THOUGHT FOR SURE HE HAD POINTED AT THE '310' IN THE WINDOW I HAD SET. I STARTED A SLOW CLB INITIALLY AND AT 17800 FT MSL THE CTLR CORRECTED US TO DSND TO 17000 FT MSL. THERE WERE NO TFC CONFLICTS ACCORDING TO THE CTLR. IMC CONDITIONS AND A BUSY SCRATCHY RADIO CONTRIBUTED TO THE CONFUSION. SUPPLEMENTAL INFO FROM ACN 631173: I RECEIVED A CLRNC FROM ATC TO 'TURN R HDG 310 VECTORS FOR CLB.' I THEN LOOKED AT MY SID PLATE TO SEE IF ANYTHING ELSE APPLIED TO OUR DEP. AS I LOOKED BACK TO THE INST PANEL I NOTICED WE WERE CLBING AND '310' WAS SET IN THE ALT WINDOW AND WE DID NOT TURN FROM OUR ORIGINAL HDG. AS I WAS ASKING THE CAPT IF HE SET THAT ALT IN THE WINDOW, THINKING I MISSED SOMETHING HERE, ATC CALLED AND ASKED OUR ALT, I SAID 17600 FT. SHE SAID TO GO BACK TO 17000 FT, WHICH WE DID. SHE THEN ASKED WHAT ALT WE WERE CLBING TO AND I SAID FL310. THEN SHE SAID THAT WAS A HDG OF 310 DEGS NOT AN ALT AND SENT US DIRECTLY TO ELIOT. THE CTLR SAID WE DID NOT CAUSE ANY PROBS.

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.