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A B747-400 on descent declared an emergency due to unable to extend the trailing edge flaps normally. Alternate extension used. Caused by false asymmetric shutoff.
| Attributes | |
| ACN | 512846 |
| Time | |
| Date | 200105 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : phl.airport |
| State Reference | PA |
| Altitude | msl single value : 4000 |
| Environment | |
| Flight Conditions | IMC |
| Weather Elements | Rain |
| Light | Dusk |
| Aircraft 1 | |
| Controlling Facilities | tracon : phl.tracon artcc : zla.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other other vortac |
| Flight Phase | descent : holding |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time total : 9000 |
| ASRS Report | 512846 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : t.e. flap position indicator other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem flight crew : declared emergency |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft Chart Or Publication |
| Primary Problem | Aircraft |
Narrative:
Could not extend flaps using normal procedures. Held at mxe VOR while troubleshooting problem. Initially concerned that flaps were locked up due to asymmetry problem, as there was a small separation of the gauge needles in the up position. Visual inspection of the flaps from cabin confirmed that they were retracted. Abnormal procedures (QRH) were accomplished for alternate flap extension. An emergency was declared. Flaps 15 degrees and leading edge extended -- approach and landing were normal. Flaps were left extended for maintenance inspection. No anomalies were found by maintenance. Procedures in QRH and CRM techniques taught by training worked well. Initial confusion and discussion was centered around trying to identify which checklist to refer to (alternate flap extension or asymmetric flap). No circuit breakers were pulled or reset (as per company policy) although maintenance merely reset 'box' which may have perceived an asymmetric situation.
Original NASA ASRS Text
Title: A B747-400 ON DSCNT DECLARED AN EMER DUE TO UNABLE TO EXTEND THE TRAILING EDGE FLAPS NORMALLY. ALTERNATE EXTENSION USED. CAUSED BY FALSE ASYMMETRIC SHUTOFF.
Narrative: COULD NOT EXTEND FLAPS USING NORMAL PROCS. HELD AT MXE VOR WHILE TROUBLESHOOTING PROB. INITIALLY CONCERNED THAT FLAPS WERE LOCKED UP DUE TO ASYMMETRY PROB, AS THERE WAS A SMALL SEPARATION OF THE GAUGE NEEDLES IN THE UP POS. VISUAL INSPECTION OF THE FLAPS FROM CABIN CONFIRMED THAT THEY WERE RETRACTED. ABNORMAL PROCS (QRH) WERE ACCOMPLISHED FOR ALTERNATE FLAP EXTENSION. AN EMER WAS DECLARED. FLAPS 15 DEGS AND LEADING EDGE EXTENDED -- APCH AND LNDG WERE NORMAL. FLAPS WERE LEFT EXTENDED FOR MAINT INSPECTION. NO ANOMALIES WERE FOUND BY MAINT. PROCS IN QRH AND CRM TECHNIQUES TAUGHT BY TRAINING WORKED WELL. INITIAL CONFUSION AND DISCUSSION WAS CTRED AROUND TRYING TO IDENT WHICH CHKLIST TO REFER TO (ALTERNATE FLAP EXTENSION OR ASYMMETRIC FLAP). NO CIRCUIT BREAKERS WERE PULLED OR RESET (AS PER COMPANY POLICY) ALTHOUGH MAINT MERELY RESET 'BOX' WHICH MAY HAVE PERCEIVED AN ASYMMETRIC SIT.
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.