B747-400
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Communication Breakdown
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Undershoot; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors; Weather; Procedure
We departed VHHH to the NE (Northeast) into convective conditions and poor visibility at flight levels. Encountered turbulence in IMC (Instrument Meteorological Conditions); some of which was not indicated by radar returns. The Captain acting as PM (Pilot Monitoring) attempted to negotiate deviations with ATC (Air Traffic Control) (Hong Kong Radar); as ATC requested we slowed to 270kts. PM stated we were heavy and would require a faster speed. ATC then issued 280kts; which was still too slow. It was very difficult to communicate with ATC due to frequency congestion. I selected speed intervene to 285kts; about 3kts above Maneuvering speed; while PM continued to attempt to request a faster speed. As we approached cruise at FL310 (31;000 ft) in IMC; radar return indicated precipitation ahead less than 5nm. PM advised maneuvering around it. HDG SEL was employed to begin a turn; but we entered convection and very quickly got a stick shaker and the airspeed went into the red by approximately 10 kts. At this time we were in IMC in a slight left bank in HDG SEL; SPD and VNAV PTH; FL310. I disconnected the Autopilot and reduced bank and angle of attack; followed by an increase in thrust to ref. Shaker ceased quickly and I began to gently pitch up. Shaker briefly activated one more time as I pitched up. I shallowed the pitch angle again and allowed the aircraft to accelerate more and gradually began to climb back to FL310; with thrust at ref. Max altitude loss for the entire event was 500-600ft. While still around 400ft low ATC advised us to maintain FL310 due to traffic at which point PM announced to ATC we had a stall; were attempting to climb to FL310 and requesting a faster speed. ATC gave us 310kts which PM entered into the MCP (Mode Control Panel) and the other FO (First Officer) verified; as we had not heard the instruction very clearly. After leveling at FL310 and accelerating; I requested right autopilot; which the PM selected. At this point the aircraft was stabilized and we were able to avoid the rest of the weather in and around the area.The most immediate reason why the stick shaker activated was the lack of sufficient margin above maneuvering speed at the time we encountered turbulence. This situation developed because we had a very high gross weight; in an area of very unstable atmosphere and yet were attempting to comply with or come close to complying with an ATC issued speed restriction. I did not see the weather on my screen until we were very close; and we had difficulty getting either relief on the airspeed or clearance to deviate due to frequency congestion. A solution may have been to simply leave the speed selected for a larger margin above maneuvering speed until relief on the airspeed restriction or deviation clear of the entire area of precipitation could be obtained.
Flight Crew flying 747-400 encountered stick shaker during climb.