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Md-11 captain reported an erroneous stick shaker activation during climb after retracting flaps.
| Attributes | |
| ACN | 1711081 |
| Time | |
| Date | 201912 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZ.TRACON |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | MD-11 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb Initial Climb |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Angle of Attack Vane |
| Person 1 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence |
Narrative:
After nearly an hour of de-icing to remove significant ice from the entire aircraft; we taxied to the runway; did a 30-second run-up; and took off normally. Flaps were retracted at approximately 180 kts. And accelerating on climb out. After flaps were up; we got both stick shakers. Copilot was flying and initially lowered the nose a few degrees from climb pitch as we looked for problems. Aoa was normal; pitch and power settings were normal for climb out; there was no auto slat extension; flaps and slats indicated up; and all 3 airspeed indicators agreed as we stabilized at 245 kts. Our initial thought was that we had faulty input to one or both fccs because everything else looked normal regarding airspeed and aoa. We also had several other intermittent warnings throughout our troubleshooting process - altitude comparator flags (even when altitude did not disagree); as comparator flags (even when airspeeds did not disagree); and pred wshear fail. We continued towards destination while we attempted to troubleshootunable to determine a definite reason for the stick shakers; we conference called [dispatch]; [maintenance control]; and md-11 chief tech pilot. After extensive discussion about how and when the stick shakers activated; and everything about airplane performance being normal; we pulled the captain stick shaker circuit breaker; and the stick shaker stopped. The first officer stick shaker circuit breaker was still operational; so the assumption seemed correct; that the cause of the stick shaker was a faulty flap position input to the #1 FCC. After we extended the flaps at destination; we reset the captain stick shaker circuit breaker; and the stick shaker did not return; which again supported the assumption that it was a faulty flap position input to FCC #1From [maintenance log] - FCC-1 fails test alpha vane N135.9. T/south per fim 22-xx-xx. Found aoa-2 sensor bearing bad not allowing sensor to move freely.
Original NASA ASRS Text
Title: MD-11 Captain reported an erroneous stick shaker activation during climb after retracting flaps.
Narrative: After nearly an hour of de-icing to remove significant ice from the entire aircraft; we taxied to the runway; did a 30-second run-up; and took off normally. Flaps were retracted at approximately 180 kts. and accelerating on climb out. After flaps were up; we got both stick shakers. Copilot was flying and initially lowered the nose a few degrees from climb pitch as we looked for problems. AOA was normal; pitch and power settings were normal for climb out; there was no Auto Slat Extension; Flaps and Slats indicated UP; and all 3 airspeed indicators agreed as we stabilized at 245 kts. Our initial thought was that we had faulty input to one or both FCCs because everything else looked normal regarding airspeed and AOA. We also had several other intermittent warnings throughout our troubleshooting process - ALT comparator flags (even when altitude did not disagree); AS comparator flags (even when airspeeds did not disagree); and PRED WSHEAR FAIL. We continued towards destination while we attempted to troubleshootUnable to determine a definite reason for the stick shakers; we conference called [Dispatch]; [Maintenance Control]; and MD-11 Chief Tech pilot. After extensive discussion about how and when the stick shakers activated; and everything about airplane performance being normal; we pulled the CAPT STICK SHAKER circuit breaker; and the stick shaker stopped. The First Officer STICK SHAKER circuit breaker was still operational; so the assumption seemed correct; that the cause of the stick shaker was a faulty flap position input to the #1 FCC. After we extended the flaps at destination; we reset the CAPT STICK SHAKER circuit breaker; and the stick shaker did NOT return; which again supported the assumption that it was a faulty flap position input to FCC #1From [Maintenance Log] - FCC-1 FAILS TEST ALPHA VANE N135.9. T/S PER FIM 22-XX-XX. FOUND AOA-2 SENSOR BEARING BAD NOT ALLOWING SENSOR TO MOVE FREELY.
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.