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Flight crew of an air carrier during cruise descent has altitude deviation when autoplt begins steep descent in IAS mode. Aircraft below gets a TCASII RA.
| Attributes | |
| ACN | 422824 |
| Time | |
| Date | 199812 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : slt |
| State Reference | MO |
| Altitude | msl bound lower : 28800 msl bound upper : 29000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Flight Phase | cruise other descent other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Commercial Fixed Wing |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 120 flight time total : 4800 flight time type : 250 |
| ASRS Report | 422824 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | altitude deviation : overshoot conflict : airborne less severe other anomaly other |
| Independent Detector | other flight crewa |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | Pilot Deviation |
Narrative:
During descent in cruise from FL330 to FL290, aircraft autoplt began steep descent in IAS mode. Captain (PF) changed to vertical speed mode which did not appear to help. Approaching FL290 (assigned), captain disconnected autoplt to stop descent. Aircraft reached FL288. Aircraft below us got RA on TCASII and descended 300 ft. We got an RA and climbed immediately to FL290.
Original NASA ASRS Text
Title: FLC OF AN ACR DURING CRUISE DSCNT HAS ALTDEV WHEN AUTOPLT BEGINS STEEP DSCNT IN IAS MODE. ACFT BELOW GETS A TCASII RA.
Narrative: DURING DSCNT IN CRUISE FROM FL330 TO FL290, ACFT AUTOPLT BEGAN STEEP DSCNT IN IAS MODE. CAPT (PF) CHANGED TO VERT SPD MODE WHICH DID NOT APPEAR TO HELP. APCHING FL290 (ASSIGNED), CAPT DISCONNECTED AUTOPLT TO STOP DSCNT. ACFT REACHED FL288. ACFT BELOW US GOT RA ON TCASII AND DSNDED 300 FT. WE GOT AN RA AND CLBED IMMEDIATELY TO FL290.
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.