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A B757-200 captain believed the autoflight system started a descent at akrij on the GPS runway 21 approach to gtf prematurely.
| Attributes | |
| ACN | 864887 |
| Time | |
| Date | 200912 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | GTF.TRACON |
| State Reference | MT |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B757 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | Direct |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Autoflight System |
| Person 1 | |
| Function | Captain Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 90 Flight Crew Total 7800 Flight Crew Type 110 |
| Events | |
| Anomaly | Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy |
Narrative:
Arrival into gtf and doing a practice GPS 21 approach. At 7000 ft MSL at noxwy IAF; I believe the aircraft software commanded an early descent 3NM from akrij down to 6200 MSL and turning inbound to the FAF and intercepting the glideslope. It is difficult to tell how early (if at all) the descent began given the close proximity of akrij to the glidepath. The segment altitude from noxwy to akrij is 7000 MSL and given the winds; aircraft speed; and turn radius it; it is possible that the turn would commence and descent be initiated prior to akrij. If possible I would recommend that all altitudes on this approach begin at 6200 MSL into akrij intersection to allow time for glide path intercept and avoid altitude deviations.
Original NASA ASRS Text
Title: A B757-200 Captain believed the autoflight system started a descent at AKRIJ on the GPS Runway 21 approach to GTF prematurely.
Narrative: Arrival into GTF and doing a practice GPS 21 approach. At 7000 FT MSL at NOXWY IAF; I believe the aircraft software commanded an early descent 3NM from AKRIJ down to 6200 MSL and turning inbound to the FAF and intercepting the glideslope. It is difficult to tell how early (if at all) the descent began given the close proximity of AKRIJ to the glidepath. The segment altitude from NOXWY to AKRIJ is 7000 MSL and given the winds; aircraft speed; and turn radius it; it is possible that the turn would commence and descent be initiated prior to AKRIJ. If possible I would recommend that all altitudes on this approach begin at 6200 MSL into AKRIJ intersection to allow time for glide path intercept and avoid altitude deviations.
Data retrieved from NASA's ASRS site as of April 2012 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.