B757 Undifferentiated or Other Model
Flight Crew Last 90 Days 110; Flight Crew Total 29000; Flight Crew Type 7000
Situational Awareness
Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors
For our departure from EWR we were given runway 4L with the Newark one departure. While climbing to our initial altitude of 3;000 feet there was moderate turbulance. ATC gave us an assigned heading which required a left turn. Prior to reaching our 3;000 foot level off altitude and still in the turn we were retracting flaps. At this time we got a momentary stick shaker activation. Corrective action was taken immediately. During this time ATC was giving further climb instructions which I did not comply with immediately. We were given the instructions again for the turn and climb and did comply once the speed was increased to normal. The rest of the flight was uneventful. I think what caused the problem was an early altitude capture causing the window to open and the throttle to retard.
The pilot flying call for VNAV at approximately 1;000 feet which was selected and verified by the FMAs after which the call was made to Departure Control. Acceleration was normal with flap retraction commanded at the appropriate schedule. Almost simultaneously; as the Pilot Flying (PF) called for flaps up; ATC issued a heading change. The selection of the new heading was interrupted to select the flaps up; after speed verification; and completed once the flap lever was in the up detent and the needle indicating movement to up. A short time later; a second heading change and a hand over to the subsequent departure controller were issued. After frequency selection; I looked out to clear the airspace in the direction of turn and about that time; still being bounced around the turbulent air; I felt the aircraft leveling. A scan of the altimeter to confirm level off at our assigned altitude indicated approximately 2;800 feet with descending needles. A glance at the VSI confirmed the descent which I immediately verbalized. Quickly scanning the speed tape I notice the airspeed in a low state; which was simultaneously accompanied by a momentary stick shaker. The PF was already applying corrective action with the throttle levers which were in the idle position. However; the autothrottle attempted to return the throttle levers to idle as it was not immediately disconnected. The PF again applied thrust and ask that I set the proper thrust setting; and with the autothrottles now disconnected; was accomplished and throttle levers returned to the PF. With the aircraft flight state stabilize; in further assessing and discussing the probable cause of the autothrottle's behavior; it became evident that the MCP speed window was open; indicating a low speed selection. I do not recall a change in FMA after verifying VNAV annunciation when it was previously selected and the speed trend and vertical rate of change during flap retraction were normal. Much of my focus was crosschecking raw data during the recovery and the assumption thus was that altitude capture came very early in the climb hence the open MCP speed window. The flight continued normally to [destination] post this event.
B757 flight crew reported getting a momentary stick shaker when the speed window opened at level off; causing the autothrottles to retard for the slower commanded speed.