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B767-300 flight crew reported conducting three ILS approaches to egll during which the flight director exhibited reverse sensing causing the aircraft to zig zag down the localizer. After two go arounds the third approach was hand flown to minimums successfully; with the flight director still oscillating.
| Attributes | |
| ACN | 1399460 |
| Time | |
| Date | 201611 |
| Place | |
| Locale Reference | EGLL.Airport |
| State Reference | FO |
| Environment | |
| Flight Conditions | IMC |
| Aircraft 1 | |
| Make Model Name | B767 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Final Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Flight Director |
| Person 1 | |
| Function | Pilot Not Flying First Officer |
| Person 2 | |
| Function | Pilot Flying Captain |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe |
Narrative:
On approach to egll briefed a CAT ii auto land due to low visibility and ceilings. Approach was normal until starting localizer intercept. Intercept angle was 30 degrees and the flight director (FD) started giving guidance that was opposite of what the raw data was showing. Eventually settled down and captured the localizer and GS. Approaching 1;500 feet AGL the localizer FMA disappeared followed by a yellow arrow through the localizer FMA and a go around was initiated. We thought that maybe the ILS critical area had been compromised and since no one else was having issues requested vectors for another ILS CAT ii to runway 9L. Cleared for the approach on about a 30 degree intercept and on localizer capture FD guidance was once again contrary to raw data and started south turning down the localizer with GS capture. There was no deviation on the GS. We again went around and were offered vectors to runway 9R. The weather had improved to CAT I minimums so the decision was made for the first officer to fly a raw data CAT I ILS. Once again the FD were giving erroneous data until about 1;000 feet AGL. Approach and landing were uneventful. Contacted egll maintenance and had a technician meet the airplane to debrief the malfunction.
Original NASA ASRS Text
Title: B767-300 flight crew reported conducting three ILS approaches to EGLL during which the flight director exhibited reverse sensing causing the aircraft to zig zag down the localizer. After two go arounds the third approach was hand flown to minimums successfully; with the flight director still oscillating.
Narrative: On approach to EGLL briefed a CAT II Auto land due to low visibility and ceilings. Approach was normal until starting LOC intercept. Intercept angle was 30 degrees and the Flight Director (FD) started giving guidance that was opposite of what the raw data was showing. Eventually settled down and captured the LOC and GS. Approaching 1;500 feet AGL the LOC FMA disappeared followed by a yellow arrow through the LOC FMA and a go around was initiated. We thought that maybe the ILS critical area had been compromised and since no one else was having issues requested vectors for another ILS CAT II to runway 9L. Cleared for the approach on about a 30 degree intercept and on LOC capture FD guidance was once again contrary to raw data and started S turning down the LOC with GS capture. There was no deviation on the GS. We again went around and were offered vectors to Runway 9R. The weather had improved to CAT I minimums so the decision was made for the First Officer to fly a raw data CAT I ILS. Once again the FD were giving erroneous data until about 1;000 feet AGL. Approach and landing were uneventful. Contacted EGLL maintenance and had a technician meet the airplane to debrief the malfunction.
Data retrieved from NASA's ASRS site 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.