B737 Undifferentiated or Other Model
Air Traffic Control Fully Certified
Situational Awareness; Training / Qualification; Communication Breakdown; Confusion
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Airspace Structure; Chart Or Publication; Procedure; Human Factors
A B737 on the FISSK3 arrival to MDW descending to FL110 was issued 'direct to HALIE Intersection; fly the Runway 4R transition'. The 737 turned toward HALIE but then descended into an IFR M-20P that was at 10;000 descending to 4;000. The B737 pilot stated he was descending on the arrival.The 'descend via' clearance is an accident waiting to happen. Whether it's because the ATC workforce has bad phraseology and the pilots interpret what we say into what they think we should have said or the pilots just don't understand that they require specific language to be able to descend on their own is irrelevant. What has happened is that ATC [the FAA] has established a procedure that has introduced risk into what had been a cut and dried situation. Prior to 'descend via' the pilot descended when instructed to do so. There was no ambiguity. Now pilots can misinterpret a phrase and cause a conflict; if not an accident.My last report was about this very situation. Last time it was an airspace deviation. This time it's a Loss of Separation. Will it be an aircraft accident next time?
When the reporter/Approach Controller cleared the B737 (descending to 11;000 FT while established on the FISSK RNAV STAR to MDW) to proceed '...direct to HALIE; fly the Runway 4R transition' the 737 crew continued their descent and suffered a loss of separation with an IFR M-20 at 10;000 FT. The flight crew advised they were descending on the arrival.