Narrative:

Was handed off from rdu departure to washington center on climbout, enroute to southbound VOR, washington issued 1 or 2 intermediate level offs enroute to filed altitude of FL240. As each level off was approached, further climb clearance was received ending with what I understood to be FL240 which I read back and acknowledged. Passing overhead south boston, leveling at FL240, heading approximately 330 degree, a different controller's voice from washington center 'your clearance was to FL230.' the captain disconnected the autopilot and began a fairly rapid descent to FL230. Center gave immediate right turn to 030, level 240. I replied we were enroute back to 230. Momentary confusion as I told captain to turn right to 030 (we were 330 degree). I asked controller what altitude he wanted us at, we were level FL230 turning right to 030. Center replied with instructions to remain at FL230, heading 360. In sorting this out with center the controller stated 'the controller I relieved said he thought he had cleared you to FL230.' I responded 'well, we read back and acknowledged FL240.' wash center replied 'our frequencies are so bad, it's almost a guess what we hear.' I was at a complete loss for words! Communications are so vital, it's obvious that one of us is wrong but unless the communications loop is complete this is likely to happen again.

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Original NASA ASRS Text

Title: ALT ASSIGNMENT MISUNDERSTANDING.

Narrative: WAS HANDED OFF FROM RDU DEP TO WASHINGTON CTR ON CLIMBOUT, ENROUTE TO SBND VOR, WASHINGTON ISSUED 1 OR 2 INTERMEDIATE LEVEL OFFS ENROUTE TO FILED ALTITUDE OF FL240. AS EACH LEVEL OFF WAS APPROACHED, FURTHER CLIMB CLRNC WAS RECEIVED ENDING WITH WHAT I UNDERSTOOD TO BE FL240 WHICH I READ BACK AND ACKNOWLEDGED. PASSING OVERHEAD SOUTH BOSTON, LEVELING AT FL240, HEADING APPROX 330 DEG, A DIFFERENT CTLR'S VOICE FROM WASHINGTON CENTER 'YOUR CLRNC WAS TO FL230.' THE CAPTAIN DISCONNECTED THE AUTOPILOT AND BEGAN A FAIRLY RAPID DESCENT TO FL230. CENTER GAVE IMMEDIATE RIGHT TURN TO 030, LEVEL 240. I REPLIED WE WERE ENROUTE BACK TO 230. MOMENTARY CONFUSION AS I TOLD CAPT TO TURN RIGHT TO 030 (WE WERE 330 DEG). I ASKED CTLR WHAT ALTITUDE HE WANTED US AT, WE WERE LEVEL FL230 TURNING RIGHT TO 030. CENTER REPLIED WITH INSTRUCTIONS TO REMAIN AT FL230, HEADING 360. IN SORTING THIS OUT WITH CENTER THE CTLR STATED 'THE CTLR I RELIEVED SAID HE THOUGHT HE HAD CLRED YOU TO FL230.' I RESPONDED 'WELL, WE READ BACK AND ACKNOWLEDGED FL240.' WASH CTR REPLIED 'OUR FREQUENCIES ARE SO BAD, IT'S ALMOST A GUESS WHAT WE HEAR.' I WAS AT A COMPLETE LOSS FOR WORDS! COMMUNICATIONS ARE SO VITAL, IT'S OBVIOUS THAT ONE OF US IS WRONG BUT UNLESS THE COMMUNICATIONS LOOP IS COMPLETE THIS IS LIKELY TO HAPPEN AGAIN.

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