Narrative:

Arriving into winnipeg with an RVR of 2600 ft; we set up for the ILS CAT 2 approach to runway 36. Previously; we had been cleared direct to dunex intersection and were level at 5000 ft approaching from a bearing of 170 degrees. At approximately 5 NM from the dunex intersection; approach control cleared us for the approach but did not reference an altitude. I did not think we could successfully fly the approach if we remained at 5000 ft. The MSA is 2900 ft and it is based on 25 NM from zww NDB and the procedure turn altitude for the approach is 2700 ft. I elected to xchk the NDB approach course on my ADI and descend to 3000 ft in order to capture the GS and complete the approach. Once on the ground; my copilot and I discussed whether the controller had assumed we would maintain 5000 ft until GS intercept or expected us to descend to 2700 ft and capture the GS. I believe most of the confusion arose because the controller did not make a reference to the altitude when clearing us for the approach. Perhaps that is primarily done in the united states.

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Original NASA ASRS Text

Title: B757-200 FLT CREW IS CLEARED FOR AN ILS APCH WHILE INBOUND TO THE FAF AT 5000 FT. THE FLT CREW INITIATED A DESCENT PRIOR TO LOC CAPTURE TO FACILITATE A STABLE APCH FOR THE LOW VISIBILITY ILS.

Narrative: ARRIVING INTO WINNIPEG WITH AN RVR OF 2600 FT; WE SET UP FOR THE ILS CAT 2 APCH TO RWY 36. PREVIOUSLY; WE HAD BEEN CLRED DIRECT TO DUNEX INTXN AND WERE LEVEL AT 5000 FT APCHING FROM A BEARING OF 170 DEGS. AT APPROX 5 NM FROM THE DUNEX INTXN; APCH CTL CLRED US FOR THE APCH BUT DID NOT REF AN ALT. I DID NOT THINK WE COULD SUCCESSFULLY FLY THE APCH IF WE REMAINED AT 5000 FT. THE MSA IS 2900 FT AND IT IS BASED ON 25 NM FROM ZWW NDB AND THE PROC TURN ALT FOR THE APCH IS 2700 FT. I ELECTED TO XCHK THE NDB APCH COURSE ON MY ADI AND DSND TO 3000 FT IN ORDER TO CAPTURE THE GS AND COMPLETE THE APCH. ONCE ON THE GND; MY COPLT AND I DISCUSSED WHETHER THE CTLR HAD ASSUMED WE WOULD MAINTAIN 5000 FT UNTIL GS INTERCEPT OR EXPECTED US TO DSND TO 2700 FT AND CAPTURE THE GS. I BELIEVE MOST OF THE CONFUSION AROSE BECAUSE THE CTLR DID NOT MAKE A REF TO THE ALT WHEN CLRING US FOR THE APCH. PERHAPS THAT IS PRIMARILY DONE IN THE UNITED STATES.

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.