A light twin aircraft on the arrival to ugn made an erroneous FMC smart turn early near veena inters...

Attributes
ACN	809747
Time
Date	200810
Place
Locale Reference	airport : ugn.airport
State Reference	IL
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mke.tracon
Operator	general aviation : personal
Make Model Name	Light Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	809747
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
ASRS Report	809748
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure non adherence : clearance other spatial deviation
Independent Detector	other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance controller : issued advisory
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

The event occurred at approximately XA56Z I was the PNF; pm. We were en route from ZZZ to ugn descending with milwaukee approach control. Route was jot-veena-ugn. Course jot-veena was 004 degrees. Clearance: cross veena at 10000 ft 250 KTS; then heading 050 degrees. Aircraft; with autoplt engaged was descending in vertical speed mode with lateral navigation engaged. 5 mi prior to veena the aircraft leveled at 10000 ft; slowing through 280 KTS for 250 KTS. Mke approach then cleared us to 8000 ft. The first officer engaged vertical speed for descent. While doing this; the FMS 'smart turned' the aircraft toward the IAF for runway 23 at ugn. The turn was estimated to be 4 mi early. Once the first officer saw this happening; he went to heading mode which was preselected for a 050 degree heading. He was going to return to a northerly heading; but we were so close to veena and the turn was so short (004-050 degrees) that he let the aircraft roll out on the 050 degree heading. ATC then gave us a 090 degree heading followed shortly after by a command to 'turn immediately to 360 degrees.' we complied with the instructions immediately and without hesitation. The controller also stated that several other aircraft have recently done the same thing leading me to believe the waypoint could be inaccurate in the FMS database. ATC advised us we were south of track and in the ord approach corridor. Error was caused by FMC 'smart turning' to the next fix even though there was a route discontinuity after veena intersection. As the PNF this all happened very quickly; leaving me very little time to react; and this happened as the first officer was engaging a descent mode on the autoplt. The error was compounded by the ATC instruction to turn further right to 090 degrees. The wind at altitude was 330 degrees at 55 KTS. Our ground track probably looked like we were past a 050 degree heading so he commanded a turn to 090 degrees which added to the track error instead of correcting it. Closer adherence to the tendency of the FMS to 'smart turn' and the use of the over-fly feature of the FMS which stops the early turn feature.

Original NASA ASRS Text

Title: A LIGHT TWIN AIRCRAFT ON THE ARRIVAL TO UGN MADE AN ERRONEOUS FMC SMART TURN EARLY NEAR VEENA INTERSECTION TOWARD THE UGN RUNWAY 23 IAF. ATC GAVE THE AIRCRAFT VECTORS OUT OF ORD AIRSPACE.

Narrative: THE EVENT OCCURRED AT APPROX XA56Z I WAS THE PNF; PM. WE WERE ENRTE FROM ZZZ TO UGN DSNDING WITH MILWAUKEE APCH CTL. RTE WAS JOT-VEENA-UGN. COURSE JOT-VEENA WAS 004 DEGS. CLRNC: CROSS VEENA AT 10000 FT 250 KTS; THEN HDG 050 DEGS. ACFT; WITH AUTOPLT ENGAGED WAS DSNDING IN VERT SPD MODE WITH LATERAL NAV ENGAGED. 5 MI PRIOR TO VEENA THE ACFT LEVELED AT 10000 FT; SLOWING THROUGH 280 KTS FOR 250 KTS. MKE APCH THEN CLRED US TO 8000 FT. THE FO ENGAGED VERT SPD FOR DSCNT. WHILE DOING THIS; THE FMS 'SMART TURNED' THE ACFT TOWARD THE IAF FOR RWY 23 AT UGN. THE TURN WAS ESTIMATED TO BE 4 MI EARLY. ONCE THE FO SAW THIS HAPPENING; HE WENT TO HDG MODE WHICH WAS PRESELECTED FOR A 050 DEG HDG. HE WAS GOING TO RETURN TO A NORTHERLY HDG; BUT WE WERE SO CLOSE TO VEENA AND THE TURN WAS SO SHORT (004-050 DEGS) THAT HE LET THE ACFT ROLL OUT ON THE 050 DEG HDG. ATC THEN GAVE US A 090 DEG HDG FOLLOWED SHORTLY AFTER BY A COMMAND TO 'TURN IMMEDIATELY TO 360 DEGS.' WE COMPLIED WITH THE INSTRUCTIONS IMMEDIATELY AND WITHOUT HESITATION. THE CTLR ALSO STATED THAT SEVERAL OTHER ACFT HAVE RECENTLY DONE THE SAME THING LEADING ME TO BELIEVE THE WAYPOINT COULD BE INACCURATE IN THE FMS DATABASE. ATC ADVISED US WE WERE S OF TRACK AND IN THE ORD APCH CORRIDOR. ERROR WAS CAUSED BY FMC 'SMART TURNING' TO THE NEXT FIX EVEN THOUGH THERE WAS A RTE DISCONTINUITY AFTER VEENA INTXN. AS THE PNF THIS ALL HAPPENED VERY QUICKLY; LEAVING ME VERY LITTLE TIME TO REACT; AND THIS HAPPENED AS THE FO WAS ENGAGING A DSCNT MODE ON THE AUTOPLT. THE ERROR WAS COMPOUNDED BY THE ATC INSTRUCTION TO TURN FURTHER R TO 090 DEGS. THE WIND AT ALT WAS 330 DEGS AT 55 KTS. OUR GND TRACK PROBABLY LOOKED LIKE WE WERE PAST A 050 DEG HDG SO HE COMMANDED A TURN TO 090 DEGS WHICH ADDED TO THE TRACK ERROR INSTEAD OF CORRECTING IT. CLOSER ADHERENCE TO THE TENDENCY OF THE FMS TO 'SMART TURN' AND THE USE OF THE OVER-FLY FEATURE OF THE FMS WHICH STOPS THE EARLY TURN FEATURE.

Data retrieved from NASA's ASRS site as of May 2009 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.

A light twin aircraft on the arrival to ugn made an erroneous FMC smart turn early near veena intersection toward the ugn runway 23 IAF. ATC gave the aircraft vectors out of ord airspace.