Narrative:

Captain's leg, we were climbing out shortly after departing from mdw, when chicago departure told us to 'turn right to 250 degrees, climb to 7000 ft.' I replied with the proper response, and the captain began moving the jet per that instruction. Passing through approximately 5500 ft, the captain asked me to query departure to confirm 7000 ft. I did, and immediately the controller replied, 'negative, 5000 ft, turn right immediately to 320 degrees, climb to 6000 ft, you have traffic at your 1 O'clock position, and need to turn now.' we immediately spotted the traffic at approximately 5+ mi away, turned to the heading, knowing this heading would clear us behind that traffic. The controller then told us to climb to 12000 ft, and to confirm we had a visual with the traffic. We did and responded once again. The controller never said anything further about the conflict, gave us another vector once level at 12000 ft, and routinely sent us to ZAU to continue our departure. Both the captain and I believed the controller had initially given us a 7000 ft initial clearance, and that I had read that altitude back to him. I think the controller meant to say 270 degrees and 5000 ft, versus 250 degrees and 7000 ft which the captain and I believed we heard him say. Upon further discussion, the captain had asked me to query the controller during the climb due to the unique altitude (7000 ft) given to us for an intermediate altitude on a typical departure from mdw. The aircraft we turned away for never got closer than 3-5 mi.

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Original NASA ASRS Text

Title: B737 DEPARTING MDW EXPERIENCED UNCERTAINTY WITH ATC ASSIGNED ALT.

Narrative: CAPT'S LEG, WE WERE CLBING OUT SHORTLY AFTER DEPARTING FROM MDW, WHEN CHICAGO DEP TOLD US TO 'TURN R TO 250 DEGS, CLB TO 7000 FT.' I REPLIED WITH THE PROPER RESPONSE, AND THE CAPT BEGAN MOVING THE JET PER THAT INSTRUCTION. PASSING THROUGH APPROX 5500 FT, THE CAPT ASKED ME TO QUERY DEP TO CONFIRM 7000 FT. I DID, AND IMMEDIATELY THE CTLR REPLIED, 'NEGATIVE, 5000 FT, TURN R IMMEDIATELY TO 320 DEGS, CLB TO 6000 FT, YOU HAVE TFC AT YOUR 1 O'CLOCK POS, AND NEED TO TURN NOW.' WE IMMEDIATELY SPOTTED THE TFC AT APPROX 5+ MI AWAY, TURNED TO THE HEADING, KNOWING THIS HEADING WOULD CLR US BEHIND THAT TFC. THE CTLR THEN TOLD US TO CLB TO 12000 FT, AND TO CONFIRM WE HAD A VISUAL WITH THE TFC. WE DID AND RESPONDED ONCE AGAIN. THE CTLR NEVER SAID ANYTHING FURTHER ABOUT THE CONFLICT, GAVE US ANOTHER VECTOR ONCE LEVEL AT 12000 FT, AND ROUTINELY SENT US TO ZAU TO CONTINUE OUR DEP. BOTH THE CAPT AND I BELIEVED THE CTLR HAD INITIALLY GIVEN US A 7000 FT INITIAL CLRNC, AND THAT I HAD READ THAT ALT BACK TO HIM. I THINK THE CTLR MEANT TO SAY 270 DEGS AND 5000 FT, VERSUS 250 DEGS AND 7000 FT WHICH THE CAPT AND I BELIEVED WE HEARD HIM SAY. UPON FURTHER DISCUSSION, THE CAPT HAD ASKED ME TO QUERY THE CTLR DURING THE CLB DUE TO THE UNIQUE ALT (7000 FT) GIVEN TO US FOR AN INTERMEDIATE ALT ON A TYPICAL DEP FROM MDW. THE ACFT WE TURNED AWAY FOR NEVER GOT CLOSER THAN 3-5 MI.

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.