Why at 600 feet was there a need for additional thrust? If the aircraft was at that stage being flown manually (I believe it is normal to disconnect the autopilot at approximately 1000 feet) had the sink rate become excessive and a need for more thrust? If so why? Sudden tailwind component or sharp drop in nosewind component?
Elementary meteorology my dear
Suggest one reads up on what the wind does as one gets closer to the surface, particularly with a HW from the L in the N hemisphere
NoD