Narrative:

Small transport X on IFR flight plan, was mistaken for a VFR call-up by approach control and was given descent clearance, then descended to within 700' and 1 1/4 mi of small aircraft Y. Center altitude alert and approach controller discovered problem at same time. Both aircraft had been worked by approach control as IFR overflts and had left approach airspace, small aircraft Y ahead, slower, and at 6000'. When small aircraft X was told to contact center, no acknowledgement was received (mistake #1) and approach controller was distracted by another aircraft call. 15 mi and 7 minutes later, small transport X at 8000', called approach control with a descent request. Controller didn't recognize aircraft call sign and wrote a VFR flight progress strip. As a VFR call-up, small transport X was assigned a low priority, and realizing controller would be unable to handle the aircraft for the next few minutes due to other duties, small transport X was advised 'altitudes your discretion' (mistake #2). Small transport X started descent. Within 2 or 3 minutes and after several questions to the aircraft, approach controller ascertained small transport X was, in fact, in IFR flight plan and advised center of the situation. At this point center controller realized small transport X had penetrated his airspace 10-15 mi and descended 1500' into small aircraft Y's airspace (allowed to wander off the airway?]) all without radio contact (mistake #3). Center 'snitch' alarmed about the same time. No evasive action required and small transport X was climbed back to 8000'. Several factors lead up to this deviation, any of which could have prevented it. Pilot didn't hear frequency change; controller didn't confirm acknowledgement; center controller didn't observe small transport X entering his airspace or descending; center controller didn't observe small aircraft Y off-course; approach controller ok'ed descent to an unidentified aircraft; and pilot accepted 'altitudes your discretion' as an IFR descent clearance (the phrase if often used for VFR operations, but never for IFR aircraft. Two asides: approach controller had just taken position so had little exposure to the aircraft call-sign, thus was confused by the later call-up. After '20 questions' by approach controller, pilot should have realized there was some confusion, and clarified his situation. Official accountability, by the way, went to approach controller.

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Original NASA ASRS Text

Title: APCH CTLR FAILED TO MAKE HANDOFF TO ARTCC ON SMT AND THEN LATER DESCENDED THE ACFT IN ARTCC AIRSPACE CAUSING A LESS THAN STANDARD SITUATION WITH AN SMA.

Narrative: SMT X ON IFR FLT PLAN, WAS MISTAKEN FOR A VFR CALL-UP BY APCH CTL AND WAS GIVEN DSCNT CLRNC, THEN DSNDED TO WITHIN 700' AND 1 1/4 MI OF SMA Y. CTR ALT ALERT AND APCH CTLR DISCOVERED PROB AT SAME TIME. BOTH ACFT HAD BEEN WORKED BY APCH CTL AS IFR OVERFLTS AND HAD LEFT APCH AIRSPACE, SMA Y AHEAD, SLOWER, AND AT 6000'. WHEN SMA X WAS TOLD TO CONTACT CTR, NO ACKNOWLEDGEMENT WAS RECEIVED (MISTAKE #1) AND APCH CTLR WAS DISTRACTED BY ANOTHER ACFT CALL. 15 MI AND 7 MINUTES LATER, SMT X AT 8000', CALLED APCH CTL WITH A DSCNT REQUEST. CTLR DIDN'T RECOGNIZE ACFT CALL SIGN AND WROTE A VFR FLT PROGRESS STRIP. AS A VFR CALL-UP, SMT X WAS ASSIGNED A LOW PRIORITY, AND REALIZING CTLR WOULD BE UNABLE TO HANDLE THE ACFT FOR THE NEXT FEW MINUTES DUE TO OTHER DUTIES, SMT X WAS ADVISED 'ALTS YOUR DISCRETION' (MISTAKE #2). SMT X STARTED DSCNT. WITHIN 2 OR 3 MINUTES AND AFTER SEVERAL QUESTIONS TO THE ACFT, APCH CTLR ASCERTAINED SMT X WAS, IN FACT, IN IFR FLT PLAN AND ADVISED CTR OF THE SITUATION. AT THIS POINT CTR CTLR REALIZED SMT X HAD PENETRATED HIS AIRSPACE 10-15 MI AND DSNDED 1500' INTO SMA Y'S AIRSPACE (ALLOWED TO WANDER OFF THE AIRWAY?]) ALL WITHOUT RADIO CONTACT (MISTAKE #3). CTR 'SNITCH' ALARMED ABOUT THE SAME TIME. NO EVASIVE ACTION REQUIRED AND SMT X WAS CLBED BACK TO 8000'. SEVERAL FACTORS LEAD UP TO THIS DEVIATION, ANY OF WHICH COULD HAVE PREVENTED IT. PLT DIDN'T HEAR FREQ CHANGE; CTLR DIDN'T CONFIRM ACKNOWLEDGEMENT; CTR CTLR DIDN'T OBSERVE SMT X ENTERING HIS AIRSPACE OR DSNDING; CTR CTLR DIDN'T OBSERVE SMA Y OFF-COURSE; APCH CTLR OK'ED DSCNT TO AN UNIDENTIFIED ACFT; AND PLT ACCEPTED 'ALTS YOUR DISCRETION' AS AN IFR DSCNT CLRNC (THE PHRASE IF OFTEN USED FOR VFR OPS, BUT NEVER FOR IFR ACFT. TWO ASIDES: APCH CTLR HAD JUST TAKEN POS SO HAD LITTLE EXPOSURE TO THE ACFT CALL-SIGN, THUS WAS CONFUSED BY THE LATER CALL-UP. AFTER '20 QUESTIONS' BY APCH CTLR, PLT SHOULD HAVE REALIZED THERE WAS SOME CONFUSION, AND CLARIFIED HIS SITUATION. OFFICIAL ACCOUNTABILITY, BY THE WAY, WENT TO APCH CTLR.

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.