Total beginner asks: Just out of interest, what would happen in this scenario?
Although not quite the same as your question, worth a read is this extract from:
REPORT 7/2003 - Date: 22 January 2003
serious incident to icelandair BOEING 757-200 at oslo airport gardermoen norway 22 january 2002
At the time, 0946 UTC, the aircraft was cleared by ATC down to 2 500 ft, and this altitude was set on the MCP. This setting was maintained through the aborted approach. The gear was selected down. When the aircraft finally was established on the LLZ, it was at least 1 dot high on the GP. Flaps 20o had been set with appropriate speed selection.The aircraft descended through 1 000 ft AAL (Above Aerodrome Level) in an unstabilized mode without the mandatory “call out”.
At an altitude of approx. 580 ft AAL (Flight Data Recorder (FDR) radio altimeter reading) the Commander decided that he discontinued the unstabilized approach and initiated a missed approach. The time was 09:49:11 UTC. He announced his decision to the First Officer and started a “Go-Around” (GA).
The status of the flight was as follows: The aircraft was above the GP, and the SOP calls for the GA altitude to be set when stabilized on GP, therefore the GA altitude was not set on the MCP. Flaps were not in landing configuration, because landing Check List was not completed. The Commander’s instrument panel indicated intermittent ILS failures of raw data without any flag warnings. The lowest altitude AAL indicated on the FDR was approx 460 ft.
The “pitch over” incident is here described mainly based on the FDR information with the Commander’s and First Officer’s reports incorporated:
When the go-around manoeuvre was started by the use of the auto go-around system, the speed was 182 kt. The aircraft was flown manually. The aircraft pitch was increased to approx. 20o and the aircraft started to climb. Upon initiating the go-around, the A/T automatically engaged and increased the thrust to the EPR (Engine Pressure Ratio) limit. In addition, the application of the under wing engine power also gave pitch up movement. During the climb the landing gear was retracted. The flight director pitch initially targeted a pitch attitude of 15o. The airspeed reached a maximum of 198 kt before it started to decrease.
Because of the aircrafts proximity to the MCP selected altitude of 2 500 ft when the go-around was started; the AFDS transitioned to Altitude Capture almost immediately after a positive rate of climb was achieved. At time 09:49:19 UTC the aircraft climbed rapidly through the MCP altitude of 2 500 ft, The FD continued to give commands targeting the MCP selected altitude. The A/T changed from go-around mode to targeting the MCP selected speed (150 kt). The maximum aircraft pitch (21o) was reached. The thrust remained near maximum because the Commander held the throttles forward. The speed was decelerating and quickly dropped below MCP speed. The pitch flight director continued to give command to lead the pilot back to the MCP altitude.
At time 09:49:34 UTC the aircraft reached a peak altitude of 2895 ft (FDR QNH corrected altitude) and the speed had decreased to 137 kt. (The reference speed for flaps 20o is 131 kt.) Nose down was applied manually by the control column. The First Officer called for “bug up” (for the flap up manoeuvring speed) to set the airspeed indicator, and the Commander pushed on the Flight Level Change Switch (FLCH) button to break the flight director altitude lock on. The speed selected on MCP was changed from 150 kt to 210 kt. During the next seconds, a full nose down input on the control column was made manually. The aircraft pitched over to an attitude of approx. –30o, and for a period of approx. 5 seconds the FDR indicates negative g-values with a maximum load factor of –0.6 g.
The control column was briefly returned to near neutral, and then another abrupt large nose down column input was made. The aircraft pitched over rapidly with the speed increasing excessively. The FDR data show that the Ground Proximity Warning System (GWPS) aural warning of “Pull up” was activated. The aircraft was now in a steep dive and rapidly descending. During the dive the flight director pitch bar gave pitch up commands relative to the pitch attitude. The A/T reduced the trust from 98% N1 to 45% N1. At time 09:49:44 UTC the aircraft pitch attitude had peaked at -49o and was beginning to increase positively.
At this time the First Officer called out “PULL UP!” - “PULL UP!”. The GPWS aural warnings of “TERRAIN” and then “TOO LOW TERRAIN” were activated. Both pilots were active at the control columns and a maximum “up” input was made. A split between left and right elevator was indicated at this time. It appears the split occurred due to both pilots being active at the controls. The pilots did not register the aural warnings. During the dive the airspeed increased to 251 kt and the lowest altitude in the recovery was 321 ft radio altitude with a peaked load factor of +3.59 g’s.