B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 205
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Aircraft Damaged; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft; Human Factors
As Pilot Flying; we encountered stick shaker upon rotation. Aircraft was flying properly but we determined the Captain's indications were inaccurate resulting in the stick shaker warning. Transferred control of the aircraft to my First Officer (FO) and we continued climbout until we had reached a safe altitude. While continuing climbout; I consulted our QRH and ran through all checklists pertinent to the conditions we encountered. Contacted Dispatch and Maintenance for guidance. Knowing that we were overweight for return; we continued with aircraft flying fine utilizing the FO's and standby instruments. Knowing that the weather enroute was VMC all the way; we continued and with fuel calculations by both ourselves and Dispatch determining that we would land with approximately 5000 pounds of fuel. With alternates available if weather conditions changed; we continued on to our destination. Arrival; approach; and landing were uneventful.Autopilot initially available and then inoperative; Captain's side IAS; AOA; and ALT disagree warnings displayed. Fuel Diff Press light intermittent the entire flight. Approximately 40 minutes into the flight with stick shaker continuous; we pulled the associated circuit breaker and silenced the stick shaker. Upon arrival; post-flight inspection revealed the Captain's side Alpha/AOA vane to be damaged. A return; while considered; should have been accomplished. A reconsideration of pulling the stick shaker circuit breaker should have been conducted.
Takeoff roll was normal; but I did notice Captain airspeed was a few knots (three to five) slower than my airspeed indicator as we were accelerating. When Captain rotated and lifted off the ground; the stick shaker activated continuously. I saw the airspeed difference now was between 10-15 knots. The Captain was PF and maintained aircraft control and rotation attitude while I crosschecked the Standby Airspeed indicator. The Standby Airspeed indicator matched my (FO side); and I told the Captain I thought his airspeed was bad. Indications now were; 'airspeed disagree' and he had no flight director. LNAV was engaged off the ground. We elected to keep climbing; using my indications; and cleaned up the aircraft based on my Mach Airspeed Indicator speeds. The Captain side airspeed indicator had the red dotted vertical line for stall speed covering the entire airspeed range; and the stick shaker was still activated. Since my indications appeared normal; we transferred aircraft control; and I flew off my instruments while the Captain became Pilot Monitoring and started consulting the QRH. We did not [advise] ATC. Cockpit indications now were: airspeed disagree; altitude disagree (2000 feet difference); AOA disagree; and a flight control FUEL DIFF PRESS light. The wind readout on the ND read 249/249 knots; so that was incorrect; but Ground Speed and TAS were correct. The Captain started reading the Airspeed Disagree Checklist; and I told ATC we were non-RVSM capable and needed an altitude below FL290. We were cleared to FL280 eastbound; and remained there for the flight. The Captain talked to Dispatch and asked if they had any ideas of the root problem; and Dispatch patched in Maintenance Control (MC). MC stated they could not troubleshoot the issue while we were flying and recommended to just follow the QRH. The nose of the aircraft was 'hunting around' in light chop; and the Flight Attendants stated the tail was swaying back and forth. The symptoms were like the Yaw Damper was disconnected; but we had no indication of that in the cockpit. The entire flight there was nothing greater than occasional light chop.After coordinating with Dispatch for the fuel burn at FL270; we made the decision to keep heading to destination; knowing we had divert options along the way; if needed. Also; we pulled the Captain stall warning stick shaker circuit breaker; and the stick shaker ceased. I hand flew the aircraft; as autopilot was not available. VNAV was not available; and there were no altitudes in the LEGS page. I informed ATC we would need an enroute descent; and we were switched to the RNAV Arrival. I hand flew the arrival and vectors to land. Approach; landing; and taxi to the gate were uneventful.Upon parking at the gate; we opened the side windows and looked at the AOA vane and pitot probes. The Captain side AOA vane was broken and bent down flush with the aircraft. We had Maintenance meet us at the gate; and we went down to the ramp to look at the broken AOA vane. It appeared as if it was just hanging by part of the metal stem. I didn't notice anything unusual during the preflight walk around. We have no idea how the vane broke; but now know the cockpit indications in flight when that happens!The only procedural and policy error we committed was pulling the Captain side circuit breaker to silence the erroneous continuous stick shaker. We believed this was the safer course of action because the FO side stick shaker could now function normally. With the Captain side stick shaker continuously activated; we would have no additional warning if the airspeed approached a stall. We thought we were preserving the validity of the warning system by pulling the malfunctioning stick shaker circuit breaker. Only today did I realize that is prohibited in the Flight Operations Manual (FOM). I didn't know about that limitation at the time. The FOM has an 'L' limitation against pulling a circuit breaker to silence any warning horn. So; unfortunately in trying to do the safer course of action; we violated an FOM limitation.
B737 Captain experienced stick shaker at rotation and after determining that the Captain's instruments are faulty; control is transferred to the First Officer. With the aircraft flying normally the crew elected to continue to destination. Post flight inspection revealed a damaged AOA vane on the Captain's side.