Narrative:

Departing changi airport on runway 20R, immediately after a widebody transport had departed on 20L, apparently on same SID the vtk 1B. Tower advised us just prior to takeoff to climb runway heading to 5000, maintain 5000. After passing vtk 8 DME, departure control instructed 'resume tekong 1B departure, contact radar.' out of 3000 we began our left turn to vtk and noticed the widebody transport at 1-2 O'clock northbound, apparently level at 5000. Radar apparently noticed the conflict at the same time as us. They asked our heading several times and just as we arrived at 4000 gave us a heading back to the right and told us to maintain 4000'. If our flight had continued to 5000 our proximity to the other aircraft would have been extremely close. The departure procedures for 20R and 20L and identical. We did not hear the clearance that widebody transport B was given but presumably we were both cleared initially to maintain 5000. Our original instruction given by the tower, to maintain runway heading would have kept us well clear. In order for the other aircraft to be at our 2 O'clock he apparently used a greater rate of turn than us, we on the other hand, were relatively light and probably reached 3000 MSL and began our turn sooner, bringing us under his aircraft. Singapore radar seemed unaware that departure had reclred us onto the SID but recognized the potential conflict almost immediately and reacted correctly, so the aircraft were never less than 1000' vertically for one another. I would recommend that since aircraft performance, airline procedures and pilot techniques vary, that the procedures from the 2 runways not be the same, that 2 almost simultaneous departures not be given the same initial altitude restriction. If the course reversal came at a specific DME rather than an altitude it would be almost impossible for one aircraft to turn inside the other. Additionally, communication on handoff between controling agencies should include any changes to previously issued clrncs or changes to original clearance.

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Original NASA ASRS Text

Title: TWO WDB ACFT DEPARTING SIN FROM PARALLEL RWYS ON SAME SID. SECOND WDB CLIMBED FASTER AND TURNED SHORTER CREATING A POTENTIAL CONFLICT THAT WAS OBSERVED BY TRACON CTLR WHO STOPPED THE SECOND WDB AT 4000' UNTIL FURTHER SEPARATION WAS ACHIEVED.

Narrative: DEPARTING CHANGI ARPT ON RWY 20R, IMMEDIATELY AFTER A WDB HAD DEPARTED ON 20L, APPARENTLY ON SAME SID THE VTK 1B. TWR ADVISED US JUST PRIOR TO TKOF TO CLIMB RWY HDG TO 5000, MAINTAIN 5000. AFTER PASSING VTK 8 DME, DEP CTL INSTRUCTED 'RESUME TEKONG 1B DEP, CONTACT RADAR.' OUT OF 3000 WE BEGAN OUR LEFT TURN TO VTK AND NOTICED THE WDB AT 1-2 O'CLOCK NBND, APPARENTLY LEVEL AT 5000. RADAR APPARENTLY NOTICED THE CONFLICT AT THE SAME TIME AS US. THEY ASKED OUR HDG SEVERAL TIMES AND JUST AS WE ARRIVED AT 4000 GAVE US A HDG BACK TO THE RIGHT AND TOLD US TO MAINTAIN 4000'. IF OUR FLT HAD CONTINUED TO 5000 OUR PROX TO THE OTHER ACFT WOULD HAVE BEEN EXTREMELY CLOSE. THE DEP PROCS FOR 20R AND 20L AND IDENTICAL. WE DID NOT HEAR THE CLRNC THAT WDB B WAS GIVEN BUT PRESUMABLY WE WERE BOTH CLRED INITIALLY TO MAINTAIN 5000. OUR ORIGINAL INSTRUCTION GIVEN BY THE TWR, TO MAINTAIN RWY HDG WOULD HAVE KEPT US WELL CLEAR. IN ORDER FOR THE OTHER ACFT TO BE AT OUR 2 O'CLOCK HE APPARENTLY USED A GREATER RATE OF TURN THAN US, WE ON THE OTHER HAND, WERE RELATIVELY LIGHT AND PROBABLY REACHED 3000 MSL AND BEGAN OUR TURN SOONER, BRINGING US UNDER HIS ACFT. SINGAPORE RADAR SEEMED UNAWARE THAT DEP HAD RECLRED US ONTO THE SID BUT RECOGNIZED THE POTENTIAL CONFLICT ALMOST IMMEDIATELY AND REACTED CORRECTLY, SO THE ACFT WERE NEVER LESS THAN 1000' VERTICALLY FOR ONE ANOTHER. I WOULD RECOMMEND THAT SINCE ACFT PERFORMANCE, AIRLINE PROCS AND PLT TECHNIQUES VARY, THAT THE PROCS FROM THE 2 RWYS NOT BE THE SAME, THAT 2 ALMOST SIMULTANEOUS DEPS NOT BE GIVEN THE SAME INITIAL ALT RESTRICTION. IF THE COURSE REVERSAL CAME AT A SPECIFIC DME RATHER THAN AN ALT IT WOULD BE ALMOST IMPOSSIBLE FOR ONE ACFT TO TURN INSIDE THE OTHER. ADDITIONALLY, COM ON HANDOFF BETWEEN CTLING AGENCIES SHOULD INCLUDE ANY CHANGES TO PREVIOUSLY ISSUED CLRNCS OR CHANGES TO ORIGINAL CLRNC.

Data retrieved from NASA's ASRS site as of August 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.