Was the F70 airborne? Then it might have been the speedbrakes. They are mainly used to reduce the speed on final approach. After touch-down (low speed) the speedbrakes are less effective. They also allow the pilots to set a higher throttle/thrust setting on final. In case of a go-around the crew simply retract the speedbrakes (and apply full power). There the engines are already at a higher power setting then normal there will be less sink rate in the beginning of the go-around. The climb out can be a lot steeper which can be useful when landing in mountainous areas.
It's not unusual when the crew make use of the speedbrakes.
Cheers,
Regional
Fokker Services Airline support