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A B737-800 pilot reports an aggressive autopilot pitch down to a minus 5 degrees at 2200 ft on an ILS approach to sea 16L. One aircraft was in position on runway 16C and otherwise no ILS interference was noted.
| Attributes | |
| ACN | 815001 |
| Time | |
| Date | 200812 |
| Local Time Of Day | 0001 To 0600 |
| Place | |
| Locale Reference | airport : sea.airport |
| State Reference | WA |
| Altitude | msl single value : 2200 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 200 flight time type : 10000 |
| ASRS Report | 815001 |
| Events | |
| Anomaly | other anomaly other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : unable |
| Supplementary | |
| Problem Areas | FAA Navigational Facility |
| Primary Problem | Navigational Facility |
Narrative:
During an autoplt B coupled ILS approach to runway 16L (approximately 2200 ft MSL; 2 NM north of dglas) autoplt aggressively pitched down to a negative 5 degrees. Autoplt was disconnected and aircraft returned to proper flight path. GS and localizer seemed normal and steady. Aircraft was flaps 5 degrees 180 KTS. One aircraft was in position on runway 16C and no other aircraft were at the north end of the airport or taking off. I don't know if this was an aircraft problem or ground based NAVAID or interference problem.
Original NASA ASRS Text
Title: A B737-800 PILOT REPORTS AN AGGRESSIVE AUTOPILOT PITCH DOWN TO A MINUS 5 DEGS AT 2200 FT ON AN ILS APPROACH TO SEA 16L. ONE AIRCRAFT WAS IN POSITION ON RUNWAY 16C AND OTHERWISE NO ILS INTERFERENCE WAS NOTED.
Narrative: DURING AN AUTOPLT B COUPLED ILS APCH TO RWY 16L (APPROX 2200 FT MSL; 2 NM N OF DGLAS) AUTOPLT AGGRESSIVELY PITCHED DOWN TO A NEGATIVE 5 DEGS. AUTOPLT WAS DISCONNECTED AND ACFT RETURNED TO PROPER FLT PATH. GS AND LOC SEEMED NORMAL AND STEADY. ACFT WAS FLAPS 5 DEGS 180 KTS. ONE ACFT WAS IN POS ON RWY 16C AND NO OTHER ACFT WERE AT THE N END OF THE ARPT OR TAKING OFF. I DON'T KNOW IF THIS WAS AN ACFT PROB OR GND BASED NAVAID OR INTERFERENCE PROB.
Data retrieved from NASA's ASRS site as of May 2009 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.