Narrative:

We were cleared via the midway SID, which among other restrictions, requires remaining within 4 DME of the field while turning to assigned headings. We departed runway 22L with clearance to climb straight out to 1300', then turn right to 090 degree, a 230 degree heading change. Surface wind was 180 degree at 13 KTS and I assume stronger at 3-4000' MSL. The first officer, who was flying, began to roll out on a heading of 290 degree instead of 090 degree. When I questioned her, she indicated that she understood the assigned heading to be 290 degree. I then attempted to verify the heading with ATC, however it took 20-30 seconds to get a word in due to frequency congestion. When I finally did get to ATC, she verified heading and we continued the turn using a maximum bank angle of 30 degree (company policy). When we completed the turn, ATC advised us we were 'in violation of the SID'. Since my DME had not locked onto the facility, I cannot verify this. The controller then gave me a phone number to call upon arriving at pittsburgh. I called the chicago TRACON 1-2 hours later and discussed the incident with a supervisor. It was a fruitful discussion and he indicated that this was just to make us aware of the reason for the 4 mi radius, to provide adequate clearance from the sears tower, a tall building. In summary, I was PIC of an aircraft which apparently deviated momentarily from a SID, I accept this. However, I must call into question a procedure which requires a heading change of 230 degree while operating at low airspeed, low altitude, complying with noise abatement procedures etc. A left turn to 090 degree would require only 130 degree heading change and would be turning us away from the sears tower, not toward it. I think maybe I should not have accepted the clearance in the first place.

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Original NASA ASRS Text

Title: ACR MLG DEVIATIES FROM ATC HEADING ASSIGNMENT ON SID FROM MDW.

Narrative: WE WERE CLRED VIA THE MIDWAY SID, WHICH AMONG OTHER RESTRICTIONS, REQUIRES REMAINING WITHIN 4 DME OF THE FIELD WHILE TURNING TO ASSIGNED HDGS. WE DEPARTED RWY 22L WITH CLRNC TO CLB STRAIGHT OUT TO 1300', THEN TURN R TO 090 DEG, A 230 DEG HDG CHANGE. SURFACE WIND WAS 180 DEG AT 13 KTS AND I ASSUME STRONGER AT 3-4000' MSL. THE F/O, WHO WAS FLYING, BEGAN TO ROLL OUT ON A HDG OF 290 DEG INSTEAD OF 090 DEG. WHEN I QUESTIONED HER, SHE INDICATED THAT SHE UNDERSTOOD THE ASSIGNED HDG TO BE 290 DEG. I THEN ATTEMPTED TO VERIFY THE HDG WITH ATC, HOWEVER IT TOOK 20-30 SECS TO GET A WORD IN DUE TO FREQ CONGESTION. WHEN I FINALLY DID GET TO ATC, SHE VERIFIED HDG AND WE CONTINUED THE TURN USING A MAX BANK ANGLE OF 30 DEG (COMPANY POLICY). WHEN WE COMPLETED THE TURN, ATC ADVISED US WE WERE 'IN VIOLATION OF THE SID'. SINCE MY DME HAD NOT LOCKED ONTO THE FAC, I CANNOT VERIFY THIS. THE CTLR THEN GAVE ME A PHONE NUMBER TO CALL UPON ARRIVING AT PITTSBURGH. I CALLED THE CHICAGO TRACON 1-2 HRS LATER AND DISCUSSED THE INCIDENT WITH A SUPVR. IT WAS A FRUITFUL DISCUSSION AND HE INDICATED THAT THIS WAS JUST TO MAKE US AWARE OF THE REASON FOR THE 4 MI RADIUS, TO PROVIDE ADEQUATE CLRNC FROM THE SEARS TWR, A TALL BUILDING. IN SUMMARY, I WAS PIC OF AN ACFT WHICH APPARENTLY DEVIATED MOMENTARILY FROM A SID, I ACCEPT THIS. HOWEVER, I MUST CALL INTO QUESTION A PROC WHICH REQUIRES A HDG CHANGE OF 230 DEG WHILE OPERATING AT LOW AIRSPD, LOW ALT, COMPLYING WITH NOISE ABATEMENT PROCS ETC. A L TURN TO 090 DEG WOULD REQUIRE ONLY 130 DEG HDG CHANGE AND WOULD BE TURNING US AWAY FROM THE SEARS TWR, NOT TOWARD IT. I THINK MAYBE I SHOULD NOT HAVE ACCEPTED THE CLRNC IN THE FIRST PLACE.

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.