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An air carrier pilot reports his aircraft pitching in response to glideslope and localizer fluctuations at 3;300 ft while flying a coupled ILS to sea runway 16L.
| Attributes | |
| ACN | 818413 |
| Time | |
| Date | 200901 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | SEA.Airport |
| State Reference | WA |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | Other Instrument Precision |
| Flight Plan | IFR |
| Person 1 | |
| Function | Captain Pilot Flying |
| Experience | Flight Crew Last 90 Days 210 Flight Crew Type 400 |
| Events | |
| Anomaly | Deviation - Procedural Published Material / Policy Inflight Event / Encounter Loss Of Aircraft Control |
Narrative:
On approach to runway 16L at sea at XA30 in IMC; the aircraft pitched up and then down fairly abruptly while coupled to the localizer and glide slope. Aircraft in IMC at 3300 ft MSL and approximately 11 DME. The crew disconnected the autopilot and the autothrottles to regain positive control of the aircraft. No further anomalies were noted on the continuation of the hand-flown approach. Stop allowing the crossing of aircraft in the ILS critical area during approaches.
Original NASA ASRS Text
Title: AN AIR CARRIER PILOT REPORTS HIS AIRCRAFT PITCHING IN RESPONSE TO GLIDESLOPE AND LOCALIZER FLUCTUATIONS AT 3;300 FT WHILE FLYING A COUPLED ILS TO SEA RUNWAY 16L.
Narrative: ON APPROACH TO RUNWAY 16L AT SEA AT XA30 IN IMC; THE AIRCRAFT PITCHED UP AND THEN DOWN FAIRLY ABRUPTLY WHILE COUPLED TO THE LOCALIZER AND GLIDE SLOPE. AIRCRAFT IN IMC AT 3300 FT MSL AND APPROXIMATELY 11 DME. THE CREW DISCONNECTED THE AUTOPILOT AND THE AUTOTHROTTLES TO REGAIN POSITIVE CONTROL OF THE AIRCRAFT. NO FURTHER ANOMALIES WERE NOTED ON THE CONTINUATION OF THE HAND-FLOWN APPROACH. STOP ALLOWING THE CROSSING OF AIRCRAFT IN THE ILS CRITICAL AREA DURING APPROACHES.
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.