B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 243
Distraction; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
Flight Crew FLC complied w / Automation / Advisory
Procedure; Human Factors
On final for 17L; runway changed to 17R and had Company 2.5 miles ahead. We were closing fast on Company and were configuring to slow. First Officer (Pilot flying (PF)) called for flaps 30. I thought I had selected flaps 30; but was distracted by Company ahead and our closure rate on him. FO called for Landing Checklist and we both verified flaps at 30. At roughly 500 feet; we got a Too Low Flaps warning. I checked the flap gauge; saw they were at 25; and moved them to 30. FO confirmed and landing was uneventful. The approach was on speed and stable except for the flap setting.
B737 Captain reports being distracted by a late runway change; resulting in the final flap setting not being set until a 'too low flaps' warning is annunciated at 500 feet.