AN ACR B737-300 FLC EXCEEDED THE 4 MI LIMIT FOR THEIR TURN COMPLETION ON THE MDW 4 DEP.

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ON MAR/XA/99; AT APPROX XA00; OUR ACR FLT BTWN MDW AND EWR WAS ISSUED THE FOLLOWING TKOF/DEP CLRNC FROM MDW TWR ON RWY 31C. 'FLY THE MDW 4 DEP; TURN R HDG 090 DEGS; CLRED FOR TKOF.' THE MIDWAY 4 DEP FOR RWY 31C NARRATIVE STATES; 'CLB ON RWY HDG UNTIL 1300 FT BEFORE TURNING ON COURSE. COMPLETE INITIALLY ASSIGNED TURN WITHIN 4 DME OF MDW; MAINTAIN 3000 FT OR ASSIGNED LOWER ALT.' WITH THE MXT LOC 109.9 TUNED TO PROVIDE DME INFO; WE MADE A NORMAL TKOF ON RWY 31C; CLBED ON RWY HDG UNTIL 1300 FT; THEN COMMENCED A R TURN TO A 090 DEG HDG; AND CLBED TO 3000 FT AS ASSIGNED AT CLEAN MANEUVERING AIRSPD. UPON CHK-IN WITH ORD DEP; THE CTLR TOLD US TO TURN FURTHER R TO HDG 120 DEGS. HE STATED WE HAD EXCEEDED THE 4 DME TURN COMPLETION REQUIREMENT OF THE MDW 4 DEP. THE FOLLOWING INFO IS NOTEWORTHY. AT NO TIME DID THE MXT LOC PROVIDE DME INFO. HAD THE DME BEEN WORKING PROPERLY; YOU SHOULD NOTE WE DEPARTED RWY 31C AND WERE ISSUED A DEP WHICH REQUIRED US TO FLY RWY HDG UNTIL 1300 FT THEN COMMENCE A R TURN TO 090 DEGS; A 140 DEG TURN. IN THIS CASE AFTER CLBING TO 1300 FT RWY HDG WHICH IS APPROX 2 MI; WE WOULD HAVE TO COMPLETE A 140 DEG TURN IN THE REMAINING 2 DME WHICH IS BEYOND THE NORMAL TURN CAPABILITIES OF THE B737-300 AT 30 DEG BANK AND 210 KIAS. IN SUMMARY; I RECOMMEND THAT A CLARIFICATION BE MADE AS TO THE MDW 4 DEP TURN REQUIREMENTS. IF THE INTENT STILL IS TO HAVE ACFT REACH 1300 FT PRIOR TO TURNING THE TURN RADIUS MUST BE REALISTIC OR AMOUNT OF TURN REDUCED.