Narrative:

I realize that the following narrative is slightly confusing for those who do not fly into mexico city often. These are some issues that have come up since mexico started using new arrival procedures. These are the issues that need to be addressed to our company; mexico ATC; and other airlines; to make the mexico operation safer. I've flown to MMMX twice since the new arrs came into effect in april. The first problem; we still have not changed our filed route of flight to reflect the new arrs. Mexico center always gives a rerte: fly paz UJ55 to datul for the datul one alpha or datul one bravo arrival. Second problem; UJ55 is not on our high charts or in our FMS navigation database. Reference to UJ55 can only be found on the MMMX chart; which shows that UJ55 goes from paz to datul to slm. This is the same routing as the datul one arrs (that can be pulled up on our FMS) and the same routing that we are always getting for our rerte from mexico center. Therefore; our flight plan filed route could be paz direct datul direct slm; since that exactly matches UJ55. Also; mexico center should be advised that we do not have UJ55 on our charts yet; and perhaps they should be giving paz direct datul as the amended routing. Third problem; the altitude and speed restrs on the MMMX commercial chart pages are depicted in a nonstandard way (boxes with arrows pointing to an arc that actually apply to numerous inbound radials). This format is a little confusing. This gotcha should be brought to every pilot's attention. Fourth problem; mexico center typically says cleared to intercept the 015 degree radial into slm and then just before you intercept the radial they typically say cleared direct to slm; datul one arrival; descend to 16000 ft. However; if you ask them if you are still required to comply with the datul one arrival speed and altitude restrs prior to slm; they say 'yes' 'absolutely' or 'affirmative.' they seem surprised that you would think anything else! It is not a good practice for them to give you a rerte to fly the arrival; then a 'helpful' but different clearance (like fly a radial that is 1 degree different than the arrival radial or to fly direct to slm; a VOR on the arrival and then continue with the arrival); then still expect you to comply with arrival restrs prior to slm. They are actually trying to be helpful; but all pilots flying into mexico should be aware that they still expect you to comply with the arrival restrs; even though they seemed to give you a different clearance. Fifth problem; many of our FMS aircraft will use their VNAV mode to fly these new MMMX arrs; and at least on the B737 VNAV path; the FMS will slow to the up bug; approaching slm; even though there is a 250 KT airspeed restr at slm. The B737 FMS calculates that you are high in relation to the airport and slows to the up bug; disregarding the airspeed restr. This VNAV gotcha may only happen on the B737-800's (I do not know); but it will inevitably reduce separation or get some crew violated at some point and our crews should be made aware of it.

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Original NASA ASRS Text

Title: A B737 CAPT EXPRESSED SOME CONCERNS ON THE OPERATIONS INTO MMMX; INCLUDING SOME AIRWAYS NOT APPEARING ON THE CHARTS; AND NON STANDARD ATC CLEARANCES AND PRACTICES.

Narrative: I REALIZE THAT THE FOLLOWING NARRATIVE IS SLIGHTLY CONFUSING FOR THOSE WHO DO NOT FLY INTO MEXICO CITY OFTEN. THESE ARE SOME ISSUES THAT HAVE COME UP SINCE MEXICO STARTED USING NEW ARR PROCS. THESE ARE THE ISSUES THAT NEED TO BE ADDRESSED TO OUR COMPANY; MEXICO ATC; AND OTHER AIRLINES; TO MAKE THE MEXICO OP SAFER. I'VE FLOWN TO MMMX TWICE SINCE THE NEW ARRS CAME INTO EFFECT IN APRIL. THE FIRST PROB; WE STILL HAVE NOT CHANGED OUR FILED RTE OF FLT TO REFLECT THE NEW ARRS. MEXICO CTR ALWAYS GIVES A RERTE: FLY PAZ UJ55 TO DATUL FOR THE DATUL ONE ALPHA OR DATUL ONE BRAVO ARR. SECOND PROB; UJ55 IS NOT ON OUR HIGH CHARTS OR IN OUR FMS NAV DATABASE. REF TO UJ55 CAN ONLY BE FOUND ON THE MMMX CHART; WHICH SHOWS THAT UJ55 GOES FROM PAZ TO DATUL TO SLM. THIS IS THE SAME ROUTING AS THE DATUL ONE ARRS (THAT CAN BE PULLED UP ON OUR FMS) AND THE SAME ROUTING THAT WE ARE ALWAYS GETTING FOR OUR RERTE FROM MEXICO CTR. THEREFORE; OUR FLT PLAN FILED RTE COULD BE PAZ DIRECT DATUL DIRECT SLM; SINCE THAT EXACTLY MATCHES UJ55. ALSO; MEXICO CTR SHOULD BE ADVISED THAT WE DO NOT HAVE UJ55 ON OUR CHARTS YET; AND PERHAPS THEY SHOULD BE GIVING PAZ DIRECT DATUL AS THE AMENDED ROUTING. THIRD PROB; THE ALT AND SPD RESTRS ON THE MMMX COMMERCIAL CHART PAGES ARE DEPICTED IN A NONSTANDARD WAY (BOXES WITH ARROWS POINTING TO AN ARC THAT ACTUALLY APPLY TO NUMEROUS INBOUND RADIALS). THIS FORMAT IS A LITTLE CONFUSING. THIS GOTCHA SHOULD BE BROUGHT TO EVERY PLT'S ATTN. FOURTH PROB; MEXICO CTR TYPICALLY SAYS CLRED TO INTERCEPT THE 015 DEG RADIAL INTO SLM AND THEN JUST BEFORE YOU INTERCEPT THE RADIAL THEY TYPICALLY SAY CLRED DIRECT TO SLM; DATUL ONE ARR; DSND TO 16000 FT. HOWEVER; IF YOU ASK THEM IF YOU ARE STILL REQUIRED TO COMPLY WITH THE DATUL ONE ARR SPD AND ALT RESTRS PRIOR TO SLM; THEY SAY 'YES' 'ABSOLUTELY' OR 'AFFIRMATIVE.' THEY SEEM SURPRISED THAT YOU WOULD THINK ANYTHING ELSE! IT IS NOT A GOOD PRACTICE FOR THEM TO GIVE YOU A RERTE TO FLY THE ARR; THEN A 'HELPFUL' BUT DIFFERENT CLRNC (LIKE FLY A RADIAL THAT IS 1 DEG DIFFERENT THAN THE ARR RADIAL OR TO FLY DIRECT TO SLM; A VOR ON THE ARR AND THEN CONTINUE WITH THE ARR); THEN STILL EXPECT YOU TO COMPLY WITH ARR RESTRS PRIOR TO SLM. THEY ARE ACTUALLY TRYING TO BE HELPFUL; BUT ALL PLTS FLYING INTO MEXICO SHOULD BE AWARE THAT THEY STILL EXPECT YOU TO COMPLY WITH THE ARR RESTRS; EVEN THOUGH THEY SEEMED TO GIVE YOU A DIFFERENT CLRNC. FIFTH PROB; MANY OF OUR FMS ACFT WILL USE THEIR VNAV MODE TO FLY THESE NEW MMMX ARRS; AND AT LEAST ON THE B737 VNAV PATH; THE FMS WILL SLOW TO THE UP BUG; APCHING SLM; EVEN THOUGH THERE IS A 250 KT AIRSPD RESTR AT SLM. THE B737 FMS CALCULATES THAT YOU ARE HIGH IN RELATION TO THE ARPT AND SLOWS TO THE UP BUG; DISREGARDING THE AIRSPD RESTR. THIS VNAV GOTCHA MAY ONLY HAPPEN ON THE B737-800'S (I DO NOT KNOW); BUT IT WILL INEVITABLY REDUCE SEPARATION OR GET SOME CREW VIOLATED AT SOME POINT AND OUR CREWS SHOULD BE MADE AWARE OF IT.

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.