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A B747-400 flight crew level at 5;000 MSL and approaching the FAF while performing an autoflight conducted RNAV overlay approach to a published NDB IAP inadvertently selected flch (flight level change) mode vice VNAV after setting the MDA (451 AGL) prior to crossing the FAF at the charted 5;000 MSL. As a result; the aircraft immediately began a descent below their cleared altitude. A relief pilot in a jumpseat and the tower controller provided alerts after a descent of about 800 ft.
| Attributes | |
| ACN | 1118622 |
| Time | |
| Date | 201309 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | EDFH.Airport |
| State Reference | FO |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Autoflight System |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Person 2 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy |
Narrative:
On arrival into edfh we were issued the NDB 03 approach at which point we set the aircraft up to perform an RNAV approach as the NDB 03 was not in the database. We were issued a final heading to intercept the inbound course and cleared to descend to 5;000 ft. The FAF; 'lulis;' [is to be crossed] at or above 5;000 ft. We intercepted the final approach course about five miles outside of lulis at 5;000 ft at which time I selected 2;100 on the MCP as this was the MDA. I then selected flch instead of VNAV which caused the aircraft to descend below the 5;000 foot restriction at lulis. At approximately 4;200 ft I realized my error and increased power to arrest the descent and climb back to 5;000 ft. At this point the tower questioned our altitude and asked us to return to 5;000 ft. I climbed to about 4;800 ft by the time we passed lulis and intercepted the glide path with no further events.
Original NASA ASRS Text
Title: A B747-400 flight crew level at 5;000 MSL and approaching the FAF while performing an autoflight conducted RNAV overlay approach to a published NDB IAP inadvertently selected FLCH (Flight Level Change) mode vice VNAV after setting the MDA (451 AGL) prior to crossing the FAF at the charted 5;000 MSL. As a result; the aircraft immediately began a descent below their cleared altitude. A Relief Pilot in a jumpseat and the Tower Controller provided alerts after a descent of about 800 FT.
Narrative: On arrival into EDFH we were issued the NDB 03 approach at which point we set the aircraft up to perform an RNAV approach as the NDB 03 was not in the database. We were issued a final heading to intercept the inbound course and cleared to descend to 5;000 FT. The FAF; 'LULIS;' [is to be crossed] at or above 5;000 FT. We intercepted the final approach course about five miles outside of LULIS at 5;000 FT at which time I selected 2;100 on the MCP as this was the MDA. I then selected FLCH instead of VNAV which caused the aircraft to descend below the 5;000 foot restriction at LULIS. At approximately 4;200 FT I realized my error and increased power to arrest the descent and climb back to 5;000 FT. At this point the Tower questioned our altitude and asked us to return to 5;000 FT. I climbed to about 4;800 FT by the time we passed LULIS and intercepted the glide path with no further events.
Data retrieved from NASA's ASRS site as of July 2013 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.