 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
While descending in flch mode; a B747-400 failed to level at the altitude set in the altitude alert window.
| Attributes | |
| ACN | 862174 |
| Time | |
| Date | 200911 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | RKSI.Airport |
| State Reference | FO |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | Vectors |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Altitude Hold/Capture |
| Person 1 | |
| Function | Pilot Flying First Officer |
| Experience | Flight Crew Last 90 Days 150 Flight Crew Total 7000 Flight Crew Type 650 |
| Person 2 | |
| Function | Other / Unknown |
| Experience | Flight Crew Last 90 Days 100 Flight Crew Total 20000 Flight Crew Type 454 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Overshoot Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT |
Narrative:
This was the first leg of the night of a two leg trip. We were on radar vectors for the ILS runway 33R approach at rksi; talking to seoul approach. We were cleared to descend and maintain 2600 feet; and given a vector of approximately 310 degrees to intercept the localizer. The captain put 2600 feet in the altitude window; and we both verified it on the pfd. We were already in a descent (in flch [flight level change] mode); so we just continued the descent in flch. We were then told by approach control that we were cleared for the ILS runway 33R approach; and to maintain 2600 feet until established. I selected the approach mode on the mode control panel; and we intercepted the localizer approximately 15 miles out; but were still in the descent to 2600 feet. At this time the glide slope was armed; but not captured; as we were still well below the glide slope driving in. Approaching 2600 feet; the aircraft did not level off; and continued to descend right through the 2600 feet that was set in the altitude window. At this time; the glide slope was still in the armed mode (not captured); indicating deflection all the way to the top of the scale. The captain noticed it first; and I reacted about 1 second later pulling back on the yoke to maintain our assigned altitude. Our altitude was approximately 2200 feet at the lowest point of deviation. Right at that moment; seoul approach notified us that they had a low altitude warning on us; and to maintain 2600 feet until established on the approach. I re-engaged the autopilot at 2600 feet; re-selected the approach mode on the mode control panel; and shot the approach to an uneventful landing. At this time; I still can't figure out why the aircraft didn't level off at 2600 feet. It is my understanding that the aircraft should have transitioned from the flch mode to altitude hold at 2600 feet until glide slope interception.
Original NASA ASRS Text
Title: While descending in FLCH mode; a B747-400 failed to level at the altitude set in the altitude alert window.
Narrative: This was the first leg of the night of a two leg trip. We were on radar vectors for the ILS Runway 33R approach at RKSI; talking to Seoul Approach. We were cleared to descend and maintain 2600 feet; and given a vector of approximately 310 degrees to intercept the localizer. The Captain put 2600 feet in the altitude window; and we both verified it on the PFD. We were already in a descent (in FLCH [Flight Level Change] mode); so we just continued the descent in FLCH. We were then told by approach control that we were cleared for the ILS Runway 33R approach; and to maintain 2600 feet until established. I selected the approach mode on the mode control panel; and we intercepted the localizer approximately 15 miles out; but were still in the descent to 2600 feet. At this time the glide slope was armed; but not captured; as we were still well below the glide slope driving in. Approaching 2600 feet; the aircraft did not level off; and continued to descend right through the 2600 feet that was set in the altitude window. At this time; the glide slope was still in the armed mode (not captured); indicating deflection all the way to the top of the scale. The Captain noticed it first; and I reacted about 1 second later pulling back on the yoke to maintain our assigned altitude. Our altitude was approximately 2200 feet at the lowest point of deviation. Right at that moment; Seoul Approach notified us that they had a low altitude warning on us; and to maintain 2600 feet until established on the approach. I re-engaged the autopilot at 2600 feet; re-selected the approach mode on the Mode Control Panel; and shot the approach to an uneventful landing. At this time; I still can't figure out why the aircraft didn't level off at 2600 feet. It is my understanding that the aircraft should have transitioned from the FLCH mode to ALT HOLD at 2600 feet until glide slope interception.
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.