B747-400
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 160; Flight Crew Total 9000; Flight Crew Type 3000
Situational Awareness
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors
We were on a 25 mile downwind. We were at 170 KIAS; flaps 20; gear up; descending through 4000 feet for 3000 feet. We were given a turn to 090 for base leg. During the turn and descent; PF must have inadvertently hit the TOGA switches on the throttles. Airplane went into a 10-12 degree nose up attitude with Go-Around thrust. PF and PM announced the TOGA status; and PF attempted to disengage both autopilot and autothrottles. Autopilot disengaged normally; and PF pushed over as airplane reached ~4200 feet. Autothrottles did not disengage; so PF manually held them in idle in an attempt to control airspeed. PF announced 'autothrottles will not disengage'; so PM turned off the autothrottle switch on the MCP. As PF tried to level the aircraft at 3000 feet (at this time the aircraft had descended to ~2900 feet); the airspeed slowed to ~156 KIAS (the top of the yellow band) and the crew got a brief stick shaker. PF immediately recovered by advancing the throttles to full power; rolled wings level and climbing back to 3000 feet. Automation was restored; ATC cleared the crew for the approach approximately 25 miles from the field; and the rest of the flight continued uneventfully.
Aircraft did what it was commanded by FMC and automation modes engaged; but not what the crew was cleared to do or what crew wanted. Being heavy; configured; low and slow complicated crew communications as aircraft took time to recover pitch and power/speed. When PF called for A/T ON; I should have selected either ALT HLD or FLCH instead of VNAV (which had been our previously selected mode); which gave us bad F/D commands and a much higher commanded speed initially. PF did a good job of recovery hand flying aircraft when split automation did not do what was expected. Lesson learned: Don't hit TO/GA switches unless needed.
B747 flight crew reported receiving a stick shaker when they lost situational awareness while dealing with the inadvertent selection of TOGA mode while on approach.