Narrative:

Cleared to skrg via medal 1 arrival. Approaching rng from north; were cleared to 13000 ft. Approaching rng we were reclred the medal 1 arrival. The arrival entails crossing the 150 degree radial 7 DME fix at or above 12000 ft to start descent inbound on the 180 degree radial to cross the rng VOR at 10000 ft as a transition to the ILS runway 36. Experience has proven that it is almost a necessity to cross the 150 degree 7 DME fix at 12000 ft in order to make the rest of the profile and have an orderly transition to the ILS. Previously we had experienced ATC issuing clearance for the ILS and then issue numerous altitude restrs that basically precluded the interception of the GS and completion of the approach. In that case we forcefully asked for clarification as to whether we were in fact cleared for the approach or not. It took a moment on that occasion; but we were then reclred for the approach just in time to catch the GS. In this case as we approached the VOR from the north we received the clearance for the medal 1; cleared for the ILS runway 36. As we departed 13000 ft I noticed a TCAS target in our 10 O'clock position 1000 ft below converging range approximately 4 mi. I glanced in that direction and sighted a set of landing lights on constant bearing (converging). There was no immediate threat but as we continued descent; crossing the VOR we received sudden further amended clearance to maintain 13000 ft. We were at 12300 ft at this time; trying to maintain the descent profile. We stated that we had been cleared for the arrival and approach. There was then some interchange of communication in spanish with what may have been the other aircraft and we were reclred for the arrival/approach. The other aircraft crossed well clear to our rear and was never heard from or seen again. Although we received no TCAS RA; it concerns us that we were able to close within 300 ft vertically and probably 2 mi of this other unidented converging target. The lights of the traffic made it to be fixed wing; probably a transport. Language communication with ATC facility is poor at best. Procedures do not appear to be in accordance with published documents. Please correct me if I am in error; but if one receives a clearance for an approach; one is cleared for the entire approach; both horizontal and vertical tracks. This is as referenced before; the second time we experienced confusing clearance at this facility. It may be that ATC is clearing us the horizontal track only when clearing us for the medal 1; however; given the proximity to crossing altitudes published on the arrival when the clearance is issued; there could be no expectation of a successful approach if one did not follow the vertical profile as well. If altitude was to be restr; I would expect a clearance such as 'cleared medal 1; maintain 13000 ft.'

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Original NASA ASRS Text

Title: B737 CAPT ON APCH TO SKRG EXPRESSED CONCERN REGARDING ATC LANGUAGE AND ALT ASSIGNMENT CLARITY DURING MEDAL 1 ARR PROC.

Narrative: CLRED TO SKRG VIA MEDAL 1 ARR. APCHING RNG FROM N; WERE CLRED TO 13000 FT. APCHING RNG WE WERE RECLRED THE MEDAL 1 ARR. THE ARR ENTAILS XING THE 150 DEG RADIAL 7 DME FIX AT OR ABOVE 12000 FT TO START DSCNT INBOUND ON THE 180 DEG RADIAL TO CROSS THE RNG VOR AT 10000 FT AS A TRANSITION TO THE ILS RWY 36. EXPERIENCE HAS PROVEN THAT IT IS ALMOST A NECESSITY TO CROSS THE 150 DEG 7 DME FIX AT 12000 FT IN ORDER TO MAKE THE REST OF THE PROFILE AND HAVE AN ORDERLY TRANSITION TO THE ILS. PREVIOUSLY WE HAD EXPERIENCED ATC ISSUING CLRNC FOR THE ILS AND THEN ISSUE NUMEROUS ALT RESTRS THAT BASICALLY PRECLUDED THE INTERCEPTION OF THE GS AND COMPLETION OF THE APCH. IN THAT CASE WE FORCEFULLY ASKED FOR CLARIFICATION AS TO WHETHER WE WERE IN FACT CLRED FOR THE APCH OR NOT. IT TOOK A MOMENT ON THAT OCCASION; BUT WE WERE THEN RECLRED FOR THE APCH JUST IN TIME TO CATCH THE GS. IN THIS CASE AS WE APCHED THE VOR FROM THE N WE RECEIVED THE CLRNC FOR THE MEDAL 1; CLRED FOR THE ILS RWY 36. AS WE DEPARTED 13000 FT I NOTICED A TCAS TARGET IN OUR 10 O'CLOCK POS 1000 FT BELOW CONVERGING RANGE APPROX 4 MI. I GLANCED IN THAT DIRECTION AND SIGHTED A SET OF LNDG LIGHTS ON CONSTANT BEARING (CONVERGING). THERE WAS NO IMMEDIATE THREAT BUT AS WE CONTINUED DSCNT; XING THE VOR WE RECEIVED SUDDEN FURTHER AMENDED CLRNC TO MAINTAIN 13000 FT. WE WERE AT 12300 FT AT THIS TIME; TRYING TO MAINTAIN THE DSCNT PROFILE. WE STATED THAT WE HAD BEEN CLRED FOR THE ARR AND APCH. THERE WAS THEN SOME INTERCHANGE OF COM IN SPANISH WITH WHAT MAY HAVE BEEN THE OTHER ACFT AND WE WERE RECLRED FOR THE ARR/APCH. THE OTHER ACFT CROSSED WELL CLR TO OUR REAR AND WAS NEVER HEARD FROM OR SEEN AGAIN. ALTHOUGH WE RECEIVED NO TCAS RA; IT CONCERNS US THAT WE WERE ABLE TO CLOSE WITHIN 300 FT VERTICALLY AND PROBABLY 2 MI OF THIS OTHER UNIDENTED CONVERGING TARGET. THE LIGHTS OF THE TFC MADE IT TO BE FIXED WING; PROBABLY A TRANSPORT. LANGUAGE COM WITH ATC FACILITY IS POOR AT BEST. PROCS DO NOT APPEAR TO BE IN ACCORDANCE WITH PUBLISHED DOCUMENTS. PLEASE CORRECT ME IF I AM IN ERROR; BUT IF ONE RECEIVES A CLRNC FOR AN APCH; ONE IS CLRED FOR THE ENTIRE APCH; BOTH HORIZ AND VERT TRACKS. THIS IS AS REFED BEFORE; THE SECOND TIME WE EXPERIENCED CONFUSING CLRNC AT THIS FACILITY. IT MAY BE THAT ATC IS CLRING US THE HORIZ TRACK ONLY WHEN CLRING US FOR THE MEDAL 1; HOWEVER; GIVEN THE PROX TO XING ALTS PUBLISHED ON THE ARR WHEN THE CLRNC IS ISSUED; THERE COULD BE NO EXPECTATION OF A SUCCESSFUL APCH IF ONE DID NOT FOLLOW THE VERT PROFILE AS WELL. IF ALT WAS TO BE RESTR; I WOULD EXPECT A CLRNC SUCH AS 'CLRED MEDAL 1; MAINTAIN 13000 FT.'

Data retrieved from NASA's ASRS site as of January 2009 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.