AN MD83 FLC RECEIVED A DSCNT CLRNC FROM LAP TRACON WHILE MMZT ARTCC HAD A BLOCKED FREQ NEAR LAP; FO.

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THE PROB OCCURRED IN OCT/99 AT XX25Z ON THE 325 DEG RADIAL 34 DME OFF OF LAPAZ; MEXICO VOR. MAZATLAN CTR FREQ HAD BEEN CONTINUOUSLY BLOCKED BY A STUCK MIKE BTWN LORETO (LTO) AND LAPAZ (LAP) YY15Z. ACFT X UNABLE TO CONTACT CTR FOR DSCNT CLRNC. IN ACCORDANCE WITH 10-7 PAGES OF OUR COMMERCIAL CHART MANUAL AND AIM PROCS; WE FOLLOWED LOST COM PROCS AND CONTACTED NEXT EXPECTED CTLR (LAPAZ CTL 120.6). LAPAZ APCH ISSUED DSCNT CLRNC. ACFT X BEGAN DSCNT AND CALLED OUT OF FL330. LAPAZ CTL CONFIRMED OUR DSCNT AND SAID TO RPT PASSING 16000 FT. LAPAZ APCH SOON THEREAFTER HAD US RECONTACT MAZATLAN CTR ON 128.0 (THE FREQ WITH THE STUCK MIKE). AFTER WE REINITIATED CONTACT WITH MAZATLAN CTR; WE WERE QUESTIONED ON OUR DSCNT CLRNC. WE ADVISED MAZATLAN CTR WE WERE CLRED THE DSCNT BY LAPAZ APCH. MAZATLAN SAID STAND BY AND CONTINUE YOUR DSCNT. WE SUGGESTED A LEVELOFF BUT MAZATLAN CTR ISSUED A DSCNT TO FL200. WE WERE THEN SWITCHED BACK TO LAPAZ APCH CTL AND THE FLT TO SJD CONTINUED NORMALLY. NO POTENTIAL CONFLICT WAS NOTED ON TCASII; VISUALLY; OR BY LAPAZ APCH. UPON ARR AT SJD; THE CAPT INQUIRED BY TELECON WITH LAPAZ APCH IF THERE WERE ANY QUESTIONS OR PROBS WITH THE DSCNT CLRNC N OF LAPAZ. LAPAZ SAID THERE WERE NO PROBS. CAUSED BY: LOST COM FAILURE OF LAPAZ APCH CTLR TO PROPERLY COORDINATE WITH MAZATLAN CTR PRIOR TO ISSUING DSCNT CLRNC. SUBMITTED TO PREVENT SIMILAR OCCURRENCE. NEEDS BETTER COORD BTWN LAPAZ APCH AND MAZATLAN CTR.