Narrative:

We were departing ont flying the prado 4 departure. At the time, we were flying radar vectors for traffic. At approximately XA00 local time, the departure controller issued us a clearance to 'fly a 100 degree heading to intercept the thermal transition on the departure, east of the pdz 130 degree radial.' I read back this clearance and proceeded to actively watch for traffic both visually and with the use of TCASII. The captain was flying, and was confused as to the controller's intentions with this clearance. He asked me to clarify our clearance, but the frequency was so busy that I couldn't get a word in. The captain understood the clearance to mean that he should fly the 100 degree heading to intercept the pdz 130 degree radial. I understood the clearance to mean that we should fly the 100 degree heading to intercept the trm 263 degree radial. (Apparently both interps are inaccurate because after looking at the departure, the only possible way to navigation an intercept of the trm 263 degree radial from our position is to intercept the sli 080 degree radial to the 59 DME changeover point. Then we could fly to trm via the 263 degree radial.) as the captain flew his own mental interpretation of our clearance (without verbalizing), he intercepted the pdz 130 degree radial and we encountered a TCASII RA of an aircraft 500 ft above us and 3 mi. We discontinued our climb, visually avoided the traffic, and then resumed our climb. The controller then contacted us to ask if we were still climbing. I told him that we received an RA, and discontinued the climb. The controller said that we were to intercept the trm 263 degree radial (not possible from our position) in order to avoid that traffic. I said that we misunderstood the clearance. We were unable to clarify the controller's intentions of our original clearance due to frequency congestion, and all of the traffic we were trying to visually avoid in that airspace. Factors: vague clearance, crew miscom, frequency congestion, GA aircraft flying in departure corridors of busy airports.

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Original NASA ASRS Text

Title: FLC OF A B727 MISUNDERSTOOD DEP CLRNC AFTER VECTORS DURING DEP ON A SID ROUTING RESULTING IN A TCASII RA AND EVASIVE ACTION BY STOPPING THEIR CLB.

Narrative: WE WERE DEPARTING ONT FLYING THE PRADO 4 DEP. AT THE TIME, WE WERE FLYING RADAR VECTORS FOR TFC. AT APPROX XA00 LCL TIME, THE DEP CTLR ISSUED US A CLRNC TO 'FLY A 100 DEG HDG TO INTERCEPT THE THERMAL TRANSITION ON THE DEP, E OF THE PDZ 130 DEG RADIAL.' I READ BACK THIS CLRNC AND PROCEEDED TO ACTIVELY WATCH FOR TFC BOTH VISUALLY AND WITH THE USE OF TCASII. THE CAPT WAS FLYING, AND WAS CONFUSED AS TO THE CTLR'S INTENTIONS WITH THIS CLRNC. HE ASKED ME TO CLARIFY OUR CLRNC, BUT THE FREQ WAS SO BUSY THAT I COULDN'T GET A WORD IN. THE CAPT UNDERSTOOD THE CLRNC TO MEAN THAT HE SHOULD FLY THE 100 DEG HDG TO INTERCEPT THE PDZ 130 DEG RADIAL. I UNDERSTOOD THE CLRNC TO MEAN THAT WE SHOULD FLY THE 100 DEG HDG TO INTERCEPT THE TRM 263 DEG RADIAL. (APPARENTLY BOTH INTERPS ARE INACCURATE BECAUSE AFTER LOOKING AT THE DEP, THE ONLY POSSIBLE WAY TO NAV AN INTERCEPT OF THE TRM 263 DEG RADIAL FROM OUR POS IS TO INTERCEPT THE SLI 080 DEG RADIAL TO THE 59 DME CHANGEOVER POINT. THEN WE COULD FLY TO TRM VIA THE 263 DEG RADIAL.) AS THE CAPT FLEW HIS OWN MENTAL INTERP OF OUR CLRNC (WITHOUT VERBALIZING), HE INTERCEPTED THE PDZ 130 DEG RADIAL AND WE ENCOUNTERED A TCASII RA OF AN ACFT 500 FT ABOVE US AND 3 MI. WE DISCONTINUED OUR CLB, VISUALLY AVOIDED THE TFC, AND THEN RESUMED OUR CLB. THE CTLR THEN CONTACTED US TO ASK IF WE WERE STILL CLBING. I TOLD HIM THAT WE RECEIVED AN RA, AND DISCONTINUED THE CLB. THE CTLR SAID THAT WE WERE TO INTERCEPT THE TRM 263 DEG RADIAL (NOT POSSIBLE FROM OUR POS) IN ORDER TO AVOID THAT TFC. I SAID THAT WE MISUNDERSTOOD THE CLRNC. WE WERE UNABLE TO CLARIFY THE CTLR'S INTENTIONS OF OUR ORIGINAL CLRNC DUE TO FREQ CONGESTION, AND ALL OF THE TFC WE WERE TRYING TO VISUALLY AVOID IN THAT AIRSPACE. FACTORS: VAGUE CLRNC, CREW MISCOM, FREQ CONGESTION, GA ACFT FLYING IN DEP CORRIDORS OF BUSY ARPTS.

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.