Narrative:

Cleared wyldd 2 (RNAV) departure. Las tower cleared us (air carrier X) for takeoff runway 25L and to report the air carrier Y flight I sight (he had just lifted off). On climb out (cleared to FL290) after passing the eyne fix en route to idale, with a programmed turn to hitme fix, the FMS calculated a turn (approximately 100 degrees) with a lead point so as not to overfly idale. Idale is not a mandatory flyover point as depicted, so the FMS made its calculations accordingly. Air carrier Y was on the same departure as us, but was closer to idale before starting his turn. Since our turn radius was inside his, and we were outclbing him, we were concerned about our separation and queried the controller while leveling off at 10000 ft MSL. His reply was our inquiry was 'why did we turn early?' there was no loss of separation and we had the air carrier Y flight in sight at all times. A different controller came on and we continued our climb. The flight continued and no more was said by the controllers. I believe that a clarification should be made whether or not the controllers expect aircraft to fly over idale or use appropriate lead points. There was nothing in the NOTAMS or on the current ATIS. Also, no speed restr is depicted, so when passing 10000 ft, the FMS calculates a turn using a faster speed, thus requiring a longer lead point. Since we were climbing faster than air carrier Y, this may have been a factor.

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Original NASA ASRS Text

Title: AN AIRBUS A310 IS PERCEIVED TO HAVE MADE AN EARLY TURN AT IDALE WHEN FLYING THE WYLDD RNAV 2 DEP FROM LAS, NV.

Narrative: CLRED WYLDD 2 (RNAV) DEP. LAS TWR CLRED US (ACR X) FOR TKOF RWY 25L AND TO RPT THE ACR Y FLT I SIGHT (HE HAD JUST LIFTED OFF). ON CLBOUT (CLRED TO FL290) AFTER PASSING THE EYNE FIX ENRTE TO IDALE, WITH A PROGRAMMED TURN TO HITME FIX, THE FMS CALCULATED A TURN (APPROX 100 DEGS) WITH A LEAD POINT SO AS NOT TO OVERFLY IDALE. IDALE IS NOT A MANDATORY FLYOVER POINT AS DEPICTED, SO THE FMS MADE ITS CALCULATIONS ACCORDINGLY. ACR Y WAS ON THE SAME DEP AS US, BUT WAS CLOSER TO IDALE BEFORE STARTING HIS TURN. SINCE OUR TURN RADIUS WAS INSIDE HIS, AND WE WERE OUTCLBING HIM, WE WERE CONCERNED ABOUT OUR SEPARATION AND QUERIED THE CTLR WHILE LEVELING OFF AT 10000 FT MSL. HIS REPLY WAS OUR INQUIRY WAS 'WHY DID WE TURN EARLY?' THERE WAS NO LOSS OF SEPARATION AND WE HAD THE ACR Y FLT IN SIGHT AT ALL TIMES. A DIFFERENT CTLR CAME ON AND WE CONTINUED OUR CLB. THE FLT CONTINUED AND NO MORE WAS SAID BY THE CTLRS. I BELIEVE THAT A CLARIFICATION SHOULD BE MADE WHETHER OR NOT THE CTLRS EXPECT ACFT TO FLY OVER IDALE OR USE APPROPRIATE LEAD POINTS. THERE WAS NOTHING IN THE NOTAMS OR ON THE CURRENT ATIS. ALSO, NO SPD RESTR IS DEPICTED, SO WHEN PASSING 10000 FT, THE FMS CALCULATES A TURN USING A FASTER SPD, THUS REQUIRING A LONGER LEAD POINT. SINCE WE WERE CLBING FASTER THAN ACR Y, THIS MAY HAVE BEEN A FACTOR.

Data retrieved from NASA's ASRS site as of July 2007 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.