Narrative:

We were cleared for descent from FL250 to FL190, assigned a heading of 150 degree to intercept the orl 309 degree right otherwise known as the leese 6 arrival to mco. Approximately 68 NM from orl we were cleared from FL190 to 17000' and given the local altimeter. I responsed by reading back the altitude and questioning the controller about a further descent to meet a hard crossing restriction at leese intersection. The first officer started his descent to 17000'. While off the frequency, I overheard the first officer saying 'we were cleared to 17000'' or something similar. I switched back to #1 radio and heard the controller give a clearance to maintain FL190. We inquired as to any conflict of traffic as the first officer initiated a climb back up to 19000'. The controller advised us that we had 17000' traffic at 3 O'clock and 3 mi. During this scenario we had descended as low as 17600' before stopping descent and climbing back to FL190. Upon arrival in orlando I called the center facility to talk with the controllers involved and was informed that they were reviewing the tapes of the incident. I called again and spoke with the supervisor who told me the controller assigned the initial clearance as follows, 'air carrier X descend to 17000' orlando altimeter 29.85? Maintain FL190' west/O any break in the transmission followed by a garbled transmission and then me questioning him about a further descent to cross leese intersection. In retrospect it seems clear to me that assuming the controller was through issuing the descent clearance after giving the altimeter setting in orlando, I read back 17000' and questioned him about the descent while he was issuing the clearance to maintain FL190, my readback of the 17000' altitude was garbled because he was still talking. The following are contributing factors in this incident. The ATC controller issuing a multiple clearance, which even if it was heard by pilots would have been confusing 'descend to 17000', orlando altimeter 29.85, maintain FL190'? Poor communication between pilot and controller. Failure of controller to hear/correct pilot's readout of lower altitude due to distraction caused by pilot questioning a future crossing restriction. Distraction of flying pilots by an additional crew member on observer's jumpseat. Supplemental information from acn 152639. Upon acknowledging our clearance to 17000', the captain questioned the controller about the expected crossing restriction of 12000' at leese intersection. We were told to stand by for a min or words to that effect. Neither the captain nor I ever heard or acknowledged a call to maintain FL190. There was a jumpseat rider on board. Conversations going on during the flight could have been distracting when listening to instructions from center. This incident was caused by a breakdown in communications between the controller and the pilots.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR DESCENDED TO AN OCCUPIED ALT DUE TO MISCOM RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: WE WERE CLRED FOR DSNT FROM FL250 TO FL190, ASSIGNED A HDG OF 150 DEG TO INTERCEPT THE ORL 309 DEG R OTHERWISE KNOWN AS THE LEESE 6 ARR TO MCO. APPROX 68 NM FROM ORL WE WERE CLRED FROM FL190 TO 17000' AND GIVEN THE LCL ALTIMETER. I RESPONSED BY READING BACK THE ALT AND QUESTIONING THE CTLR ABOUT A FURTHER DSNT TO MEET A HARD XING RESTRICTION AT LEESE INTXN. THE F/O STARTED HIS DSNT TO 17000'. WHILE OFF THE FREQ, I OVERHEARD THE F/O SAYING 'WE WERE CLRED TO 17000'' OR SOMETHING SIMILAR. I SWITCHED BACK TO #1 RADIO AND HEARD THE CTLR GIVE A CLRNC TO MAINTAIN FL190. WE INQUIRED AS TO ANY CONFLICT OF TFC AS THE F/O INITIATED A CLB BACK UP TO 19000'. THE CTLR ADVISED US THAT WE HAD 17000' TFC AT 3 O'CLOCK AND 3 MI. DURING THIS SCENARIO WE HAD DSNDED AS LOW AS 17600' BEFORE STOPPING DSNT AND CLBING BACK TO FL190. UPON ARR IN ORLANDO I CALLED THE CTR FAC TO TALK WITH THE CTLRS INVOLVED AND WAS INFORMED THAT THEY WERE REVIEWING THE TAPES OF THE INCIDENT. I CALLED AGAIN AND SPOKE WITH THE SUPVR WHO TOLD ME THE CTLR ASSIGNED THE INITIAL CLRNC AS FOLLOWS, 'ACR X DSND TO 17000' ORLANDO ALTIMETER 29.85? MAINTAIN FL190' W/O ANY BREAK IN THE XMISSION FOLLOWED BY A GARBLED XMISSION AND THEN ME QUESTIONING HIM ABOUT A FURTHER DSNT TO CROSS LEESE INTXN. IN RETROSPECT IT SEEMS CLR TO ME THAT ASSUMING THE CTLR WAS THROUGH ISSUING THE DSNT CLRNC AFTER GIVING THE ALTIMETER SETTING IN ORLANDO, I READ BACK 17000' AND QUESTIONED HIM ABOUT THE DSNT WHILE HE WAS ISSUING THE CLRNC TO MAINTAIN FL190, MY READBACK OF THE 17000' ALT WAS GARBLED BECAUSE HE WAS STILL TALKING. THE FOLLOWING ARE CONTRIBUTING FACTORS IN THIS INCIDENT. THE ATC CTLR ISSUING A MULTIPLE CLRNC, WHICH EVEN IF IT WAS HEARD BY PLTS WOULD HAVE BEEN CONFUSING 'DSND TO 17000', ORLANDO ALTIMETER 29.85, MAINTAIN FL190'? POOR COM BTWN PLT AND CTLR. FAILURE OF CTLR TO HEAR/CORRECT PLT'S READOUT OF LOWER ALT DUE TO DISTR CAUSED BY PLT QUESTIONING A FUTURE XING RESTRICTION. DISTR OF FLYING PLTS BY AN ADDITIONAL CREW MEMBER ON OBSERVER'S JUMPSEAT. SUPPLEMENTAL INFO FROM ACN 152639. UPON ACKNOWLEDGING OUR CLRNC TO 17000', THE CAPT QUESTIONED THE CTLR ABOUT THE EXPECTED XING RESTRICTION OF 12000' AT LEESE INTXN. WE WERE TOLD TO STAND BY FOR A MIN OR WORDS TO THAT EFFECT. NEITHER THE CAPT NOR I EVER HEARD OR ACKNOWLEDGED A CALL TO MAINTAIN FL190. THERE WAS A JUMPSEAT RIDER ON BOARD. CONVERSATIONS GOING ON DURING THE FLT COULD HAVE BEEN DISTRACTING WHEN LISTENING TO INSTRUCTIONS FROM CTR. THIS INCIDENT WAS CAUSED BY A BREAKDOWN IN COMS BTWN THE CTLR AND THE PLTS.

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.