Narrative:

While holding short for departure on 12R in sat, tower cleared us for takeoff on 12R with no specific heading assignment (not even to 'fly runway heading'). At about 1000 ft, the captain began a left turn to intercept the 359 degree radial from sat as depicted on alamo 2 SID (with henley transition). At the same time, we were told by tower to 'contact departure.' departure queried our heading, which at time we were flying through 040 degrees. He then issued instructions for us to maintain our current heading, which I reported as 010 degrees. He questioned what is heading sat tower had assigned us, then located traffic at our 11 O'clock position that was descending to pass below us. There was no conflict with the traffic. Our TCASII didn't show any TA/RA or TA. The controller explained that the SID said to 'fly runway heading for vector to assigned route.' we continued the flight without incident. In my opinion the tower controller should have assigned runway heading along with the takeoff clearance to further enhance SID instructions.

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Original NASA ASRS Text

Title: FLC OF ACR LGT ACFT TURNED PREMATURELY FROM THE RWY HDG AFTER TKOF DUE TO A LACK OF 'SID' CLRNC UNDERSTANDING.

Narrative: WHILE HOLDING SHORT FOR DEP ON 12R IN SAT, TWR CLRED US FOR TKOF ON 12R WITH NO SPECIFIC HDG ASSIGNMENT (NOT EVEN TO 'FLY RWY HDG'). AT ABOUT 1000 FT, THE CAPT BEGAN A L TURN TO INTERCEPT THE 359 DEG RADIAL FROM SAT AS DEPICTED ON ALAMO 2 SID (WITH HENLEY TRANSITION). AT THE SAME TIME, WE WERE TOLD BY TWR TO 'CONTACT DEP.' DEP QUERIED OUR HDG, WHICH AT TIME WE WERE FLYING THROUGH 040 DEGS. HE THEN ISSUED INSTRUCTIONS FOR US TO MAINTAIN OUR CURRENT HDG, WHICH I RPTED AS 010 DEGS. HE QUESTIONED WHAT IS HDG SAT TWR HAD ASSIGNED US, THEN LOCATED TFC AT OUR 11 O'CLOCK POS THAT WAS DSNDING TO PASS BELOW US. THERE WAS NO CONFLICT WITH THE TFC. OUR TCASII DIDN'T SHOW ANY TA/RA OR TA. THE CTLR EXPLAINED THAT THE SID SAID TO 'FLY RWY HDG FOR VECTOR TO ASSIGNED RTE.' WE CONTINUED THE FLT WITHOUT INCIDENT. IN MY OPINION THE TWR CTLR SHOULD HAVE ASSIGNED RWY HDG ALONG WITH THE TKOF CLRNC TO FURTHER ENHANCE SID INSTRUCTIONS.

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.