Narrative:

We were cleared from mdw via mdw 4 departure (SID) as filed. Our takeoff clearance from runway 22L called for a right turn to a heading of 110 degrees (long way around -- 250 degree turn), which must be completed within 4 DME of mdw. I put a heading of 110 degrees in the MCP window and on initial climb requested the captain (PNF) to select heading at 1300 ft per procedure. The flight director commanded a left turn (quickest way) to heading 110 degrees so I had to ignore v-bars and turn right to comply with procedure. This may have caused a momentary hesitation on my part and initially I could have banked more aggressively (30 degree bank). As we leveled off, departure control stated 'that you must stay within 4 DME of mdw and there's a possible conflict with an ord departure at 2300 ft, 5 mi away.' the captain saw the traffic and noted his DME reading 3.8 DME. To assist the captain and to reduce workload, I requested to have him engage the right autoplt. As it engaged and since the flight director still commanded a left turn, the aircraft rolled out and initiated a left turn (opposite). I immediately disconnected the autoplt and banked right as instructed, compensating for the early rollout by banking greater than 30 degrees. In the process we may have exceeded the 4 DME limit. We did not note the actual DME. After rolling out on the correct heading, we were given a frequency change and the following statement from the departure controller, 'today was ok but for planning purposes, in the future you must stay within 4 DME.' the wind (estimated 250 degrees at 30 KTS) tailwind most of the turn, may have been a contributing factor. A 250 degree turn right after takeoff is also a bit extreme. It was also my first time flying out of mdw on the B757. It's a very busy departure and I wish had briefed it better and controled the flight director and autoplt correctly by 'leading' the turn on the heading selector (turn it slowly, less than 180 degrees in the right direction). Callback conversation with reporter revealed the following information: the reporter advised this was his first departure from mdw. Complying with the large scale turn within the 4 mi limit requires some modifications to the normal takeoff procedure for his aircraft, primarily a slower airspeed to minimize the turn radius. His company has since instituted a special takeoff procedure to ensure compliance with the 4 DME limit.

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Original NASA ASRS Text

Title: ASSIGNED A 250 DEG R-HAND TURN ON DEP, FLT CREW OF B757 FLYING MIDWAY DEP PROC EXCEED 4 DME LIMIT FROM MDW.

Narrative: WE WERE CLRED FROM MDW VIA MDW 4 DEP (SID) AS FILED. OUR TKOF CLRNC FROM RWY 22L CALLED FOR A R TURN TO A HDG OF 110 DEGS (LONG WAY AROUND -- 250 DEG TURN), WHICH MUST BE COMPLETED WITHIN 4 DME OF MDW. I PUT A HDG OF 110 DEGS IN THE MCP WINDOW AND ON INITIAL CLB REQUESTED THE CAPT (PNF) TO SELECT HDG AT 1300 FT PER PROC. THE FLT DIRECTOR COMMANDED A L TURN (QUICKEST WAY) TO HDG 110 DEGS SO I HAD TO IGNORE V-BARS AND TURN R TO COMPLY WITH PROC. THIS MAY HAVE CAUSED A MOMENTARY HESITATION ON MY PART AND INITIALLY I COULD HAVE BANKED MORE AGGRESSIVELY (30 DEG BANK). AS WE LEVELED OFF, DEP CTL STATED 'THAT YOU MUST STAY WITHIN 4 DME OF MDW AND THERE'S A POSSIBLE CONFLICT WITH AN ORD DEP AT 2300 FT, 5 MI AWAY.' THE CAPT SAW THE TFC AND NOTED HIS DME READING 3.8 DME. TO ASSIST THE CAPT AND TO REDUCE WORKLOAD, I REQUESTED TO HAVE HIM ENGAGE THE R AUTOPLT. AS IT ENGAGED AND SINCE THE FLT DIRECTOR STILL COMMANDED A L TURN, THE ACFT ROLLED OUT AND INITIATED A L TURN (OPPOSITE). I IMMEDIATELY DISCONNECTED THE AUTOPLT AND BANKED R AS INSTRUCTED, COMPENSATING FOR THE EARLY ROLLOUT BY BANKING GREATER THAN 30 DEGS. IN THE PROCESS WE MAY HAVE EXCEEDED THE 4 DME LIMIT. WE DID NOT NOTE THE ACTUAL DME. AFTER ROLLING OUT ON THE CORRECT HDG, WE WERE GIVEN A FREQ CHANGE AND THE FOLLOWING STATEMENT FROM THE DEP CTLR, 'TODAY WAS OK BUT FOR PLANNING PURPOSES, IN THE FUTURE YOU MUST STAY WITHIN 4 DME.' THE WIND (ESTIMATED 250 DEGS AT 30 KTS) TAILWIND MOST OF THE TURN, MAY HAVE BEEN A CONTRIBUTING FACTOR. A 250 DEG TURN RIGHT AFTER TKOF IS ALSO A BIT EXTREME. IT WAS ALSO MY FIRST TIME FLYING OUT OF MDW ON THE B757. IT'S A VERY BUSY DEP AND I WISH HAD BRIEFED IT BETTER AND CTLED THE FLT DIRECTOR AND AUTOPLT CORRECTLY BY 'LEADING' THE TURN ON THE HDG SELECTOR (TURN IT SLOWLY, LESS THAN 180 DEGS IN THE RIGHT DIRECTION). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR ADVISED THIS WAS HIS FIRST DEP FROM MDW. COMPLYING WITH THE LARGE SCALE TURN WITHIN THE 4 MI LIMIT REQUIRES SOME MODIFICATIONS TO THE NORMAL TKOF PROC FOR HIS ACFT, PRIMARILY A SLOWER AIRSPD TO MINIMIZE THE TURN RADIUS. HIS COMPANY HAS SINCE INSTITUTED A SPECIAL TKOF PROC TO ENSURE COMPLIANCE WITH THE 4 DME LIMIT.

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.