Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Inflight Event / Encounter Unstabilized Approach
Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented; Flight Crew Executed Go Around / Missed Approach
Aircraft; Human Factors
While configuring on final; the Captain (CA) selected gear down and flaps 15 about one and a half miles outside the ILS marker. Speed was 170; autopilot was off; autothrottes on. Vref was set at 144 knots. As the aircraft continued to slow; the CA called for flaps 25. I then noticed both the amber min maneuver bar and red min airspeed bar were rising close to our current speed. I asked the CA if he wanted flaps 30. He set his bug speed back to 150 knots. I had set flaps to 25. At that point; the red bar rose above our indicated speed of 150. I looked at the speed window and saw 'a150'. We simultaneously got the 'airspeed low; airspeed low' callout; and the throttles were advancing. We executed a go-around uneventfully. On the subsequent approach; we configured early and slowly looking for reoccurrence; but approach and landing were normal.We suspect a flap indication malfunction.Closely checking the position of the red bar for reasonableness throughout configuration; and be ready to execute go around with conflicting indications.
B737-800 First Officer reported an airspeed deviation during approach that resulted in a go-around.