Narrative:

The flight departed kbna at XA10Z via the nashville 8 departure (SID) for kmcd as destination. J-45 airway was joined via radar vectors en route to atl VOR. The flight was proceeding at FL260 and 300 KIAS. ZTL (133.17) gave us clearance to climb to FL330 (our flight plan filed altitude). We acknowledged the clearance and requested to deviate to a hdging of 150 degrees for WX (our course was 145 degrees).center asked if that would be a turn to the right or left and we responded 'to the right'. Center controller then responded 'deviation' to the right heading 150 degrees approved, maintain two eight zero for the climb'. The clearance was readback and a climb was begun to FL330 and speed reduced to 289 KIAS. Passing FL290, center asked our altitude and we responded, passing FL290 for FL330. After a pause, he cleared us again up to FL330, but indicated that he had planned for us to level at FL280. He stated that there was no problem, that it wasn't an issue. Both pilots agreed that no 'FL280' was given by the controller. We subsequently asked the controller if there had been any problem or conflict created. He stated that there was no conflict or problem and not to be concerned. There were no TCASII TA's or cautions at any time. Believe the misunderstanding occurred because the atl controller failed to state 'cleared to FL280' vice, 'maintain two eight zero for the climb'. This terminology led the crew to believe 280 was the airspeed desired for the climb due to the deviation for WX and possible other air traffic. Also, 280 KIAS is a normal airspeed, often given us during climb by ATC for sequencing, ie, the previous leg from kdtw to kbna. Additionally, ATC controllers are almost unanimously consistent in relaying altitude assignments prefaced by flight level. Also, FL280 is not the normal hemispherical altitude for our aforementioned direction of flight. Believe these considerations contributed to any misunderstanding. Also, the other pilot repeated the clearance readback verbatim, rather than adding 'KIAS' behind the 'maintain 280 for the climb which might have keyed the controller to review what he had actually said. This was the fourth leg of the second day of a four day pairing. The crew had flown together 2 previous pairings for the month. Don't believe any fatigue factors, etc, were involved.

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Original NASA ASRS Text

Title: A B737-300 CAPT REPORTED THAT ZTL USED NONSTANDARD PHRASEOLOGY FOR MAINTAINING AN ALT, WHICH HE MISTOOK AND HIS FO READBACK, AS AN AIRSPD RESTR WHILE CLBING TO A DIFFERENT ALT.

Narrative: THE FLT DEPARTED KBNA AT XA10Z VIA THE NASHVILLE 8 DEP (SID) FOR KMCD AS DEST. J-45 AIRWAY WAS JOINED VIA RADAR VECTORS ENRTE TO ATL VOR. THE FLT WAS PROCEEDING AT FL260 AND 300 KIAS. ZTL (133.17) GAVE US CLRNC TO CLB TO FL330 (OUR FLT PLAN FILED ALT). WE ACKNOWLEDGED THE CLRNC AND REQUESTED TO DEVIATE TO A HDGING OF 150 DEGS FOR WX (OUR COURSE WAS 145 DEGS).CTR ASKED IF THAT WOULD BE A TURN TO THE R OR L AND WE RESPONDED 'TO THE R'. CTR CTLR THEN RESPONDED 'DEV' TO THE R HDG 150 DEGS APPROVED, MAINTAIN TWO EIGHT ZERO FOR THE CLB'. THE CLRNC WAS READBACK AND A CLB WAS BEGUN TO FL330 AND SPD REDUCED TO 289 KIAS. PASSING FL290, CTR ASKED OUR ALT AND WE RESPONDED, PASSING FL290 FOR FL330. AFTER A PAUSE, HE CLRED US AGAIN UP TO FL330, BUT INDICATED THAT HE HAD PLANNED FOR US TO LEVEL AT FL280. HE STATED THAT THERE WAS NO PROB, THAT IT WASN'T AN ISSUE. BOTH PLTS AGREED THAT NO 'FL280' WAS GIVEN BY THE CTLR. WE SUBSEQUENTLY ASKED THE CTLR IF THERE HAD BEEN ANY PROB OR CONFLICT CREATED. HE STATED THAT THERE WAS NO CONFLICT OR PROB AND NOT TO BE CONCERNED. THERE WERE NO TCASII TA'S OR CAUTIONS AT ANY TIME. BELIEVE THE MISUNDERSTANDING OCCURRED BECAUSE THE ATL CTLR FAILED TO STATE 'CLRED TO FL280' VICE, 'MAINTAIN TWO EIGHT ZERO FOR THE CLB'. THIS TERMINOLOGY LED THE CREW TO BELIEVE 280 WAS THE AIRSPD DESIRED FOR THE CLB DUE TO THE DEVIATION FOR WX AND POSSIBLE OTHER AIR TFC. ALSO, 280 KIAS IS A NORMAL AIRSPD, OFTEN GIVEN US DURING CLB BY ATC FOR SEQUENCING, IE, THE PREVIOUS LEG FROM KDTW TO KBNA. ADDITIONALLY, ATC CTLRS ARE ALMOST UNANIMOUSLY CONSISTENT IN RELAYING ALT ASSIGNMENTS PREFACED BY FLT LEVEL. ALSO, FL280 IS NOT THE NORMAL HEMISPHERICAL ALT FOR OUR AFOREMENTIONED DIRECTION OF FLT. BELIEVE THESE CONSIDERATIONS CONTRIBUTED TO ANY MISUNDERSTANDING. ALSO, THE OTHER PLT REPEATED THE CLRNC READBACK VERBATIM, RATHER THAN ADDING 'KIAS' BEHIND THE 'MAINTAIN 280 FOR THE CLB WHICH MIGHT HAVE KEYED THE CTLR TO REVIEW WHAT HE HAD ACTUALLY SAID. THIS WAS THE FOURTH LEG OF THE SECOND DAY OF A FOUR DAY PAIRING. THE CREW HAD FLOWN TOGETHER 2 PREVIOUS PAIRINGS FOR THE MONTH. DON'T BELIEVE ANY FATIGUE FACTORS, ETC, WERE INVOLVED.

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.