Narrative:

Departed runway 24L with an original clearance to do the toronto 6 departure which is to track the 237 degree inbound course to juliet rbn and then 230 degree heading for vectors to course. The SID states follow SID noise track until above 3600 ft. It also states remain on track towards the appropriate NDB until instructed to turn. Prior to brake release tower gave us instructions to fly heading 240 degrees or runway heading, not sure which was the exact phrase. On departure maintained runway heading, 240 degrees, until instructed to turn to a more swesterly heading. Not sure of exact heading instructed to turn to. Began the turn at approximately 2000 ft. As I rolled out of the turn my first officer said he thought we were to hold the turn until reaching 3600 ft. I felt that we were to turn at the time the controller issued the instruction. I felt also that because we were given a heading to fly on takeoff this basically negated our requirement to fly the SID unless instructed to return to the SID. I feel this SID is written in an ambiguous way in that the 2 of us interpreted the intent of the SID differently. I felt that the phrase 'remain on track until instructed to turn,' meant that one should turn when controller said to. My first officer felt that we were required to continue on the assigned heading until reaching 3600 ft and then turn to the heading assigned by the departure controller, even though there is a time delay between instruction to turn and actual execution of the turn. If the intent of the SID is to have no turns before 3600 ft then I think that should be stated more clearly and/or the controller should not issue a turn until he observes the altitude readout to be 3600 ft or if he issues the turn earlier we should state turn to heading such and such at 3600 ft. Again, I feel that there is ambiguity built into this SID and a definite trap one could fall into if a turn instruction is issued to you prior to reaching 3600 ft.

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Original NASA ASRS Text

Title: FLC NOT SURE HOW TO FLY THE SID WHEN THEY RECEIVED AN AMENDED CLRNC.

Narrative: DEPARTED RWY 24L WITH AN ORIGINAL CLRNC TO DO THE TORONTO 6 DEP WHICH IS TO TRACK THE 237 DEG INBOUND COURSE TO JULIET RBN AND THEN 230 DEG HDG FOR VECTORS TO COURSE. THE SID STATES FOLLOW SID NOISE TRACK UNTIL ABOVE 3600 FT. IT ALSO STATES REMAIN ON TRACK TOWARDS THE APPROPRIATE NDB UNTIL INSTRUCTED TO TURN. PRIOR TO BRAKE RELEASE TWR GAVE US INSTRUCTIONS TO FLY HDG 240 DEGS OR RWY HDG, NOT SURE WHICH WAS THE EXACT PHRASE. ON DEP MAINTAINED RWY HDG, 240 DEGS, UNTIL INSTRUCTED TO TURN TO A MORE SWESTERLY HDG. NOT SURE OF EXACT HDG INSTRUCTED TO TURN TO. BEGAN THE TURN AT APPROX 2000 FT. AS I ROLLED OUT OF THE TURN MY FO SAID HE THOUGHT WE WERE TO HOLD THE TURN UNTIL REACHING 3600 FT. I FELT THAT WE WERE TO TURN AT THE TIME THE CTLR ISSUED THE INSTRUCTION. I FELT ALSO THAT BECAUSE WE WERE GIVEN A HDG TO FLY ON TKOF THIS BASICALLY NEGATED OUR REQUIREMENT TO FLY THE SID UNLESS INSTRUCTED TO RETURN TO THE SID. I FEEL THIS SID IS WRITTEN IN AN AMBIGUOUS WAY IN THAT THE 2 OF US INTERPRETED THE INTENT OF THE SID DIFFERENTLY. I FELT THAT THE PHRASE 'REMAIN ON TRACK UNTIL INSTRUCTED TO TURN,' MEANT THAT ONE SHOULD TURN WHEN CTLR SAID TO. MY FO FELT THAT WE WERE REQUIRED TO CONTINUE ON THE ASSIGNED HDG UNTIL REACHING 3600 FT AND THEN TURN TO THE HDG ASSIGNED BY THE DEP CTLR, EVEN THOUGH THERE IS A TIME DELAY BTWN INSTRUCTION TO TURN AND ACTUAL EXECUTION OF THE TURN. IF THE INTENT OF THE SID IS TO HAVE NO TURNS BEFORE 3600 FT THEN I THINK THAT SHOULD BE STATED MORE CLRLY AND/OR THE CTLR SHOULD NOT ISSUE A TURN UNTIL HE OBSERVES THE ALT READOUT TO BE 3600 FT OR IF HE ISSUES THE TURN EARLIER WE SHOULD STATE TURN TO HDG SUCH AND SUCH AT 3600 FT. AGAIN, I FEEL THAT THERE IS AMBIGUITY BUILT INTO THIS SID AND A DEFINITE TRAP ONE COULD FALL INTO IF A TURN INSTRUCTION IS ISSUED TO YOU PRIOR TO REACHING 3600 FT.

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.