Narrative:

Being vectored from the northwest to ILS 28R at pit. Was on 090 degree heading until 17 DME from mmj VOR. Then right turn to 180 degrees was given and a descent from 6000 to 5000'. Then further right to 250 degrees to intercept localizer and was cleared for approach. Upon reaching 250 degree heading I was further directed to 'turn further right, heading 270 degrees to intercept, descend to 4000'.' I read this back and copilot, who was flying, started the descent out of 5000' while intercepting the localizer. When passing through 4500' the controller gave me climb immediately to 5000', 'you have traffic off your left at 4000', maintain 5000 until kerrs intersection and call the tower at kerrs.' I responded, 'out of 4500 for 5000, you had cleared me to 4000. We (the copilot and I) both copied that I read that back to you.' the controller's reply was only, 'roger.' I reaffirmed I was cleared for the approach and then called the tower. The approach controller was on 124.15 MHZ. The copilot agreed that he had heard the clearance to descend from 5000 to 4000'. The approach plate for the ILS to runway 28R states 'mandatory' to cross kerrs intersection at 5000'. Callback conversation with reporter revealed the following: controller said nothing about loss of sep, except as stated aircraft on the parallel approach. Has heard nothing further on the incident.

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Original NASA ASRS Text

Title: OPERROR WHEN CTLR ISSUED DESCENT CLRNC TO ACR MLG ON PARALLEL APCH BEFORE LEGAL POINT.

Narrative: BEING VECTORED FROM THE NW TO ILS 28R AT PIT. WAS ON 090 DEG HDG UNTIL 17 DME FROM MMJ VOR. THEN RIGHT TURN TO 180 DEGS WAS GIVEN AND A DSCNT FROM 6000 TO 5000'. THEN FURTHER RIGHT TO 250 DEGS TO INTERCEPT LOC AND WAS CLRED FOR APCH. UPON REACHING 250 DEG HDG I WAS FURTHER DIRECTED TO 'TURN FURTHER RIGHT, HDG 270 DEGS TO INTERCEPT, DSND TO 4000'.' I READ THIS BACK AND COPLT, WHO WAS FLYING, STARTED THE DSCNT OUT OF 5000' WHILE INTERCEPTING THE LOC. WHEN PASSING THROUGH 4500' THE CTLR GAVE ME CLB IMMEDIATELY TO 5000', 'YOU HAVE TFC OFF YOUR LEFT AT 4000', MAINTAIN 5000 UNTIL KERRS INTXN AND CALL THE TWR AT KERRS.' I RESPONDED, 'OUT OF 4500 FOR 5000, YOU HAD CLRED ME TO 4000. WE (THE COPLT AND I) BOTH COPIED THAT I READ THAT BACK TO YOU.' THE CTLR'S REPLY WAS ONLY, 'ROGER.' I REAFFIRMED I WAS CLRED FOR THE APCH AND THEN CALLED THE TWR. THE APCH CTLR WAS ON 124.15 MHZ. THE COPLT AGREED THAT HE HAD HEARD THE CLRNC TO DSND FROM 5000 TO 4000'. THE APCH PLATE FOR THE ILS TO RWY 28R STATES 'MANDATORY' TO CROSS KERRS INTXN AT 5000'. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: CTLR SAID NOTHING ABOUT LOSS OF SEP, EXCEPT AS STATED ACFT ON THE PARALLEL APCH. HAS HEARD NOTHING FURTHER ON THE INCIDENT.

Data retrieved from NASA's ASRS site as of August 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.