Narrative:

I was training on radar on the R6 position. My trainee initially cleared air carrier X to 'cross wever intersection at and maintain 100'. 2 mins later, as the traffic situation changed, my trainee reclred air carrier X to 'descend and maintain FL230'. (For traffic at FL220.) the pilot read back the correct clearance. We issued traffic to both aircraft, however, air carrier X did not respond. By the time we tried to issue traffic a second time to air carrier X, the aircraft had descended thru his assigned altitude or FL230 resulting in a near miss due to pilot deviation. The pilot still thought he was cleared to 10,000'. I think this incident could have been avoided if when my trainee reclred air carrier X, he had said 'air carrier X, amend altitude (or revised altitude), descend and maintain FL230'. Supplemental information from acn 124182: I advised ZMA of our position, 'tadpo intersection at 290'. The ZMA controller cleared us to 'miami airport, after marathon, the dolan arrival cross wever at 10,000'. At this time I set 10,000' in the altitude alerter. A few mins later I asked my first officer to pick up the miami ATIS. During this time I received instructions for ZMA, 'air carrier X descend to 230'. I responded with 'roger down to 230 taking her out of 29'. I adjusted the autoplt controller to descend, and advised my first officer, who had just finished copying the miami ATIS, stating 'center wants us out of 230, I've started the autoplt down, sounds like he wants us down quickly, so descend at a rate slightly higher than normal until we get below 230, we are still cleared to 10'. I contacted ZMA by telephone at approximately XX00 local. After exchanging introductions, the watch chief stated that a review of the tapes indicates, we came within less than 4 mi of an air carrier Y that was at FL220.

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Original NASA ASRS Text

Title: ACR DESCENDED BELOW ASSIGNED ALT.

Narrative: I WAS TRAINING ON RADAR ON THE R6 POSITION. MY TRAINEE INITIALLY CLRED ACR X TO 'CROSS WEVER INTXN AT AND MAINTAIN 100'. 2 MINS LATER, AS THE TFC SITUATION CHANGED, MY TRAINEE RECLRED ACR X TO 'DSND AND MAINTAIN FL230'. (FOR TFC AT FL220.) THE PLT READ BACK THE CORRECT CLRNC. WE ISSUED TFC TO BOTH ACFT, HOWEVER, ACR X DID NOT RESPOND. BY THE TIME WE TRIED TO ISSUE TFC A SECOND TIME TO ACR X, THE ACFT HAD DESCENDED THRU HIS ASSIGNED ALT OR FL230 RESULTING IN A NEAR MISS DUE TO PLT DEVIATION. THE PLT STILL THOUGHT HE WAS CLRED TO 10,000'. I THINK THIS INCIDENT COULD HAVE BEEN AVOIDED IF WHEN MY TRAINEE RECLRED ACR X, HE HAD SAID 'ACR X, AMEND ALT (OR REVISED ALT), DSND AND MAINTAIN FL230'. SUPPLEMENTAL INFORMATION FROM ACN 124182: I ADVISED ZMA OF OUR POSITION, 'TADPO INTXN AT 290'. THE ZMA CTLR CLRED US TO 'MIAMI ARPT, AFTER MARATHON, THE DOLAN ARR CROSS WEVER AT 10,000'. AT THIS TIME I SET 10,000' IN THE ALT ALERTER. A FEW MINS LATER I ASKED MY F/O TO PICK UP THE MIAMI ATIS. DURING THIS TIME I RECEIVED INSTRUCTIONS FOR ZMA, 'ACR X DSND TO 230'. I RESPONDED WITH 'ROGER DOWN TO 230 TAKING HER OUT OF 29'. I ADJUSTED THE AUTOPLT CTLR TO DSND, AND ADVISED MY F/O, WHO HAD JUST FINISHED COPYING THE MIAMI ATIS, STATING 'CENTER WANTS US OUT OF 230, I'VE STARTED THE AUTOPLT DOWN, SOUNDS LIKE HE WANTS US DOWN QUICKLY, SO DSND AT A RATE SLIGHTLY HIGHER THAN NORMAL UNTIL WE GET BELOW 230, WE ARE STILL CLRED TO 10'. I CONTACTED ZMA BY TELEPHONE AT APPROX XX00 LOCAL. AFTER EXCHANGING INTRODUCTIONS, THE WATCH CHIEF STATED THAT A REVIEW OF THE TAPES INDICATES, WE CAME WITHIN LESS THAN 4 MI OF AN ACR Y THAT WAS AT FL220.

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.