PLTDEV.

Narrative

ACR X LEVEL AT FL180 WAS GIVEN CLRNC TO FL210 TO BE AT OR ABOVE FL190 IN 1 1/2 MIN. ACR X ACKNOWLEDGED; AND COMPLIED. HOWEVER; ACR Y CLBED TO FL210. WHEN I CAUGHT ACR Y'S CLB THROUGH 17000 FT; I REQUESTED HE STAY AT 17000 FT HIS ASSIGNED ALT. HE REPLIED HE HAD FL210 IN THE BOX. I TURNED HIM R TO A 090 DEG HDG AND REQUESTED HE DSND TO 17000 FT. MIL Z AT FL180 WAS THEN TURNED L TO A 360 DEG HDG. I NEVER HEARD ACR Y ACKNOWLEDGE CLRNC. ACR X MUST HAVE CUT HIM OUT. IN REVIEWING THE TAPE; I DID NOT HEAR ACR Y ACKNOWLEDGE THE CLRNC GIVEN TO ACR X. HOWEVER; I HEARD ACR X ACKNOWLEDGE AND OBSERVED HIM CLB TO FL210. ACR Y WAS PREVIOUSLY CLRED TO 17000 FT AND WAS STILL CLBING OUT OF 13000 FT CLBING TO 17000 FT. THERE ARE 3 UHF AND 3 VHF FREQS AT PAB SECTOR. (125.55/398.9- 127.1/290.4-127.4/269.4). 1 PLT BLOCKED THE OTHER OUT. THESE 6 FREQS ARE A DEFINITE PROB AT THIS SECTOR. SUPPLEMENTAL INFO FROM ACN 286552: I WAS ACTING AS PNF AND USING THE PA SYS TO SPEAK WITH OUR PAX. I WAS DOING THIS AS WE WERE CLBING THROUGH APPROX 13000 FT. UPON RESUMING 'HEADS-UP' ACTIVE FLT DUTIES WE WERE CLBING THROUGH APPROX 17000 FT. THE CAPT ADVISED ME WE HAD BEEN TOLD TO EXPEDITE CLB TO FL210. AS WE CLBED THROUGH APPROX 17200 FT ATC QUESTIONED WHAT ALT WE WERE CLBING TO AND I RESPONDED THAT WE HAD BEEN CLRED TO FL210. ZID SAID THAT OUR CLRNC WAS 17000 FT; TOLD US TO DSND IMMEDIATELY TO 17000 FT AND TURN R TO 090 DEG WHICH WE DID. WE HAD VISUAL CONTACT WITH ANOTHER ACFT APPROX 5 MI AWAY; ABOVE US; AND AT OUR APPROX 10-11 O'CLOCK POS. THERE DID NOT SEEM TO BE A CONFLICT. TCASII DID NOT ALERT. THE CAPT REITERATED THE CLRNC HE HAD RECEIVED (FL210) TO ATC BUT WE WERE TOLD THAT OUR CLRNC WAS TO 17000 FT. I DO NOT KNOW WHY THE CTLR DID NOT CORRECT THE CAPT WHEN HE READ BACK THE CLRNC TO FL210. OFTENTIMES THE CTLRS ARE EXTREMELY BUSY AS ARE PLTS. SOMETIMES FREQS ARE CONGESTED; CALL SIGNS ARE SIMILAR; CTLRS DON'T ACKNOWLEDGE BECAUSE 'THEY ARE ON THE OTHER LINE' (PLTS INCLUDED) -- SOMETIMES THINGS ARE JUST VERY BUSY AND THERE IS A LOT OF 'STUFF' GOING ON. SUPPLEMENTAL INFO FROM ACN 286952: 2ND ACFT TURBO PROP MIL C26 IFR.