Narrative:

We were given 33000 ft for the crossing by shanwick clearance. We were level at FL310 when checking in with london control. I asked for FL330 as that was our altitude for the crossing. The controller responded that he would check. Several mins later controller called us back and cleared us to climb to FL350. I called him back saying we wanted FL330 and, if we could not have that, we would rather stay at FL310. As I was talking to the controller the first officer reset the mode control panel to FL350 and began a vertical speed climb to FL350. After my second request for FL330, the first officer understood the controller to say maintain FL330 now. First officer then reseet the MCP to FL330. I responded to the controller to maintain FL310. I did not see the first officer change the mode control panel or initiate the vertical speed climb. Approximately 1 min later, london control called and said we were not given authorization to climb, descend back to FL310. We were at FL322 and promptly descended. Strict adherence to our altitude window setting procedures would have avoided this. Supplemental information from acn 302787: the captain said he had given us initial climb to FL350 and, when he called back, he heard him say maintain FL310 when I heard maintain FL330 now. The captain said he had not noticed I had started the climb as he was busy talking with the controller over our FL330 altitude clearance request. I had reset the mode control panel as he was discussing our altitude of FL330 so I could climb to our initial cleared altitude of FL350. I had thought the captain saw it.

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Original NASA ASRS Text

Title: ALTDEV OVER THE ATLANTIC.

Narrative: WE WERE GIVEN 33000 FT FOR THE XING BY SHANWICK CLRNC. WE WERE LEVEL AT FL310 WHEN CHKING IN WITH LONDON CTL. I ASKED FOR FL330 AS THAT WAS OUR ALT FOR THE XING. THE CTLR RESPONDED THAT HE WOULD CHK. SEVERAL MINS LATER CTLR CALLED US BACK AND CLRED US TO CLB TO FL350. I CALLED HIM BACK SAYING WE WANTED FL330 AND, IF WE COULD NOT HAVE THAT, WE WOULD RATHER STAY AT FL310. AS I WAS TALKING TO THE CTLR THE FO RESET THE MODE CTL PANEL TO FL350 AND BEGAN A VERT SPD CLB TO FL350. AFTER MY SECOND REQUEST FOR FL330, THE FO UNDERSTOOD THE CTLR TO SAY MAINTAIN FL330 NOW. FO THEN RESEET THE MCP TO FL330. I RESPONDED TO THE CTLR TO MAINTAIN FL310. I DID NOT SEE THE FO CHANGE THE MODE CTL PANEL OR INITIATE THE VERT SPD CLB. APPROX 1 MIN LATER, LONDON CTL CALLED AND SAID WE WERE NOT GIVEN AUTHORIZATION TO CLB, DSND BACK TO FL310. WE WERE AT FL322 AND PROMPTLY DSNDED. STRICT ADHERENCE TO OUR ALT WINDOW SETTING PROCS WOULD HAVE AVOIDED THIS. SUPPLEMENTAL INFO FROM ACN 302787: THE CAPT SAID HE HAD GIVEN US INITIAL CLB TO FL350 AND, WHEN HE CALLED BACK, HE HEARD HIM SAY MAINTAIN FL310 WHEN I HEARD MAINTAIN FL330 NOW. THE CAPT SAID HE HAD NOT NOTICED I HAD STARTED THE CLB AS HE WAS BUSY TALKING WITH THE CTLR OVER OUR FL330 ALT CLRNC REQUEST. I HAD RESET THE MODE CTL PANEL AS HE WAS DISCUSSING OUR ALT OF FL330 SO I COULD CLB TO OUR INITIAL CLRED ALT OF FL350. I HAD THOUGHT THE CAPT SAW IT.

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.