B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 9000
Distraction; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors; Weather
The event took place in about 5-10 seconds and everything happened so fast that I am not 100% sure about every event; but I will give my best recollection...The Captain was hand flying. As we approached level off at 8000 feet (assigned altitude) during climb out; the FMS speed dropped off; reducing the auto throttle power. I went heads down to try and figure out why the speeds dropped out; then the throttle and FMS speed kicked back in and advanced the throttle. The subtraction and then addition of power caused us to climb to about 8;300 feet. ATC alerted us to the deviation and we returned to 8;000 feet. I think the distraction of having the auto throttles drop out and back on at a critical moment caused us to loose Situational Awareness. For me personally.... this event emphasizes the importance of 'the Big Picture'...and don't let a little thing become a big thing. Altitude awareness might be the single most important item to monitor in the cock pit. [During prior employment] I saw hundreds of SOP's for cockpit procedures. One procedure I really liked was an 'Approaching' callout when 100 feet from level off altitude. To me this was a last chance callout to bring your attention back to the altimeter. I wish we used this procedure.
I was Captain; acting as Pilot Flying on this leg. Autopilot not engaged during incident. Presentation displays normal; and in VNAV mode. During departure; assigned heading 040 degrees and climb to altitude of 8000 feet MSL. During climb; on assigned heading; after aircraft cleanup and at a speed of 250 KIAS; the aircraft entered a broken to overcast layer of clouds; with accompanying increasing turbulence at an altitude of approximately 6800 feet MSL. I was manually flying the aircraft with reference to the HUD display. I made a verbal statement passing 7000 feet for 8000 feet; which was acknowledged by the First Officer (Pilot Monitoring). At approximately 7400 feet; the aircraft encountered a moderate turbulence 'jolt'. The flight director; 'pitch steering bar' blanked; and was followed by a commanded airspeed increasing from the indicated 250 KIAS; up to 280 KIAS on the airspeed indication tape. I announced the indication loss and change of commanded airspeed to the PM; which was acknowledged. I became distracted by the unusual display occurrence. Now passing 7800 feet; I realized the aircraft auto throttles were not going to retard power in order to level off at 8000 feet. I manually overrode the auto throttles to idle without disconnecting the auto throttles; and then took my hand away to select another flight mode (Level Change) in an attempt to restore the flight director pitch display. The pitch display returned and the airspeed window opened to show 280 knots. By this time the aircraft had passed through the assigned altitude of 8000 feet MSL; reaching an altitude of 8300 feet MSL. ATC (Departure Control) made a radio transmission stating that our assigned altitude was 8000 feet MSL; and for us to descend to 8000 feet MSL immediately. The PM acknowledged the radio call; and stated that we were in moderate chop; and descending to 8000 feet. I selected a speed of 250 knots on the MCP; and again manually retarded the throttles to idle; while decreasing pitch; in attempt to return to assigned altitude. Still in moderate turbulence in clouds complicated the maneuver. Decrease in selected airspeed and accompanying pitch reduction allowed the aircraft to descend and return to assigned altitude of 8000 feet MSL. I am unaware of the total time that the aircraft was above the assigned altitude of 8000 feet MSL. Highest variation from assigned altitude noted was 300 feet. After achieving assigned altitude; ATC gave another vector and climb to a different assigned altitude. Climbing above the overcast layer on assigned heading and achieving VMC conditions; we noted a building cumulus cloud on our assigned vector. I requested the PM to notify ATC that we needed a turn to the left or right to avoid. With delay in response from ATC; I exercised Captain's authority; and deviated from assigned heading to the left; and then returned to assigned heading passing the building cumulus cloud. Prior to clearing the cloud; we were again given a clearance to continue climbing to a higher altitude; and cleared to an enroute fix on the RNAV departure. Distraction by unusual PFD display and instrument presentation from what was expected; and increasing occurrence of turbulence caused me to lose situational awareness and inadvertently climb through assigned altitude. When there is a recognizable situation where the aircraft will enter IMC conditions; engaging the autopilot; allowing the pilot flying to monitor performance and instrument display; would greatly reduce workload and help maintain and preserve situational awareness.
B737NG flight crew reported exceeding assigned altitude by three hundred feet caused by turbulence and auto thrust malfunction at the time of level off.