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A cpr flight crew en route to dtw deviated from ATC instructions while flying the polar one arrival by descending below their assigned altitude.
| Attributes | |
| ACN | 430339 |
| Time | |
| Date | 199903 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | intersection : polar |
| State Reference | MI |
| Altitude | msl single value : 12000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : d21.tracon |
| Operator | general aviation : corporate |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | other vortac |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : polar 1 |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : corporate |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 102 flight time total : 14000 flight time type : 1812 |
| ASRS Report | 430339 |
| Person 2 | |
| Affiliation | company : corporate |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : instrument pilot : commercial |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : published procedure |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | controller : provided flight assist flight crew : returned to original clearance |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
On an IFR flight from apa to dtw with an IFR clearance via mkg and the polar one arrival to dtw we were cleared to cross polar intersection at 12000 ft. Upon reaching polar intersection following a rapid descent (the FMS programmed for the next possible altitude restr of 6000 ft after scubi intersection) and thinking I needed to cross scubi at 6000 ft, also observing the FMS giving a high rate of descent to cross the perceived restr I began descent from 12000 ft and at the same time requesting a verification from the ATC controller. The controller came right back with negative maintain 12000 ft. I immediately returned to 12000 ft observing no other aircraft in the vicinity and no returns on the TCASII. I feel a more thorough review of the arrival and the reading of the arrival text rather than looking only at the expect altitude clearance limits may have prevented the altitude excursion. Also most important I should never have deviated before verifying the clearance.
Original NASA ASRS Text
Title: A CPR FLC ENRTE TO DTW DEVIATED FROM ATC INSTRUCTIONS WHILE FLYING THE POLAR ONE ARR BY DSNDING BELOW THEIR ASSIGNED ALT.
Narrative: ON AN IFR FLT FROM APA TO DTW WITH AN IFR CLRNC VIA MKG AND THE POLAR ONE ARR TO DTW WE WERE CLRED TO CROSS POLAR INTXN AT 12000 FT. UPON REACHING POLAR INTXN FOLLOWING A RAPID DSCNT (THE FMS PROGRAMMED FOR THE NEXT POSSIBLE ALT RESTR OF 6000 FT AFTER SCUBI INTXN) AND THINKING I NEEDED TO CROSS SCUBI AT 6000 FT, ALSO OBSERVING THE FMS GIVING A HIGH RATE OF DSCNT TO CROSS THE PERCEIVED RESTR I BEGAN DSCNT FROM 12000 FT AND AT THE SAME TIME REQUESTING A VERIFICATION FROM THE ATC CTLR. THE CTLR CAME RIGHT BACK WITH NEGATIVE MAINTAIN 12000 FT. I IMMEDIATELY RETURNED TO 12000 FT OBSERVING NO OTHER ACFT IN THE VICINITY AND NO RETURNS ON THE TCASII. I FEEL A MORE THOROUGH REVIEW OF THE ARR AND THE READING OF THE ARR TEXT RATHER THAN LOOKING ONLY AT THE EXPECT ALT CLRNC LIMITS MAY HAVE PREVENTED THE ALT EXCURSION. ALSO MOST IMPORTANT I SHOULD NEVER HAVE DEVIATED BEFORE VERIFYING THE CLRNC.
Data retrieved from NASA's ASRS site as of July 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.