Narrative:

We were in level flight at FL280, anticipating a climb to final cruise altitude of FL350. Captain was flying the aircraft on autoplt; I was working the radios. I left the radio to make the seatbelt sign PA so the captain momentarily had both flying and radio duties. While I was making the PA, the captain answered a radio call and began a climb with FL330 set in the altitude alert. Immediately after I returned to the radio, as the aircraft was climbing through approximately FL300, the center controller asked our altitude, then immediately issued a descent clearance to FL290 and a heading change to 270 degree, followed by a request to expedite descent for traffic. This was followed shorty by a clearance to FL280 and request to expedite. In the meantime, another aircraft was issued a heading change for traffic. We were level at FL280 within 1 min of the initial clearance to FL290. Center then asked to what altitude we believed we had been cleared. The captain indicated FL330 to me and I radioed that to the controller. Controller responded that a mistake was made somewhere. Since I was not monitoring the radio at the time the climb was started, I did not hear the clearance and cannot say if a mistake was made on our part. There were however a couple of similar sounding callsigns on the frequency and the center controller had inadvertently used the wrong company prefix to our callsign in previous transmissions, so the possibility of misunderstanding certainly existed. In addition, we had been held low for quite some time and were expecting clearance to a higher altitude. In two man crew airplanes it is impossible for both pilots to monitor the radio at all times, therefore it is of paramount importance the controllers carefully monitor clearance readbacks, to avoid potential misunderstandings, especially when similar callsigns are on the frequency.

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Original NASA ASRS Text

Title: CAPT OF ACR MLG HEARS CLRNC TO FL330 WHILE FO IS MAKING PA ANNOUNCEMENT. CTLR GIVES IMMEDIATE DESCENT AND AVOIDANCE VECTORS BECAUSE THERE HAD APPARENTLY BEEN A MISUNDERSTANDING BY THE FLT CREW OR AN ERRONEOUS INSTRUCTION BY ATC AS A RESULT OF SIMILIAR SOUNDING CALLSIGN ON THE FREQ.

Narrative: WE WERE IN LEVEL FLT AT FL280, ANTICIPATING A CLB TO FINAL CRUISE ALT OF FL350. CAPT WAS FLYING THE ACFT ON AUTOPLT; I WAS WORKING THE RADIOS. I LEFT THE RADIO TO MAKE THE SEATBELT SIGN PA SO THE CAPT MOMENTARILY HAD BOTH FLYING AND RADIO DUTIES. WHILE I WAS MAKING THE PA, THE CAPT ANSWERED A RADIO CALL AND BEGAN A CLB WITH FL330 SET IN THE ALT ALERT. IMMEDIATELY AFTER I RETURNED TO THE RADIO, AS THE ACFT WAS CLBING THROUGH APPROX FL300, THE CENTER CTLR ASKED OUR ALT, THEN IMMEDIATELY ISSUED A DSNT CLRNC TO FL290 AND A HDG CHANGE TO 270 DEG, FOLLOWED BY A REQUEST TO EXPEDITE DSNT FOR TFC. THIS WAS FOLLOWED SHORTY BY A CLRNC TO FL280 AND REQUEST TO EXPEDITE. IN THE MEANTIME, ANOTHER ACFT WAS ISSUED A HDG CHANGE FOR TFC. WE WERE LEVEL AT FL280 WITHIN 1 MIN OF THE INITIAL CLRNC TO FL290. CENTER THEN ASKED TO WHAT ALT WE BELIEVED WE HAD BEEN CLRED. THE CAPT INDICATED FL330 TO ME AND I RADIOED THAT TO THE CTLR. CTLR RESPONDED THAT A MISTAKE WAS MADE SOMEWHERE. SINCE I WAS NOT MONITORING THE RADIO AT THE TIME THE CLB WAS STARTED, I DID NOT HEAR THE CLRNC AND CANNOT SAY IF A MISTAKE WAS MADE ON OUR PART. THERE WERE HOWEVER A COUPLE OF SIMILAR SOUNDING CALLSIGNS ON THE FREQ AND THE CENTER CTLR HAD INADVERTENTLY USED THE WRONG COMPANY PREFIX TO OUR CALLSIGN IN PREVIOUS TRANSMISSIONS, SO THE POSSIBILITY OF MISUNDERSTANDING CERTAINLY EXISTED. IN ADDITION, WE HAD BEEN HELD LOW FOR QUITE SOME TIME AND WERE EXPECTING CLRNC TO A HIGHER ALT. IN TWO MAN CREW AIRPLANES IT IS IMPOSSIBLE FOR BOTH PLTS TO MONITOR THE RADIO AT ALL TIMES, THEREFORE IT IS OF PARAMOUNT IMPORTANCE THE CTLRS CAREFULLY MONITOR CLRNC READBACKS, TO AVOID POTENTIAL MISUNDERSTANDINGS, ESPECIALLY WHEN SIMILAR CALLSIGNS ARE ON THE FREQ.

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.