B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
General None Reported / Taken
Human Factors
I was PF and had briefed a CAT 3 Eval. The weather was day VFR with good meteorological conditions. We were on approach and gotten vectors to intercept the localizer for 25R; then were cleared for the approach; maintaining 170 knots. We were not handed off to tower; so the PNF switched over to tower himself and the tower controller cleared us to land on 25R and suggested where we could plan to turn off. The approach seemed stable; and we prepared for landing. I looked up and saw the landing light on. I believed at that point that the before landing checklist was complete. At less than 500 AGL the 'Too low; Terrain' warning sounded. I stated something to the effect that it was not a valid warning; and we were in agreement that terrain was not an issue. Being day VFR on short final; with what I deemed a stabilized approach; I dismissed the warning as a nuisance and continued the approach. As the approach continued; the PNF told me that the flaps were not fully extended. I believed I was still at flaps 25. Our target speed for flaps 30 was to be 150; but 170 was still in the window. Believing the flaps to be at 25; I accepted a target speed of 170 for that setting and I continued the approach and landing. We had an 11;000 foot runway and turned off at our planned taxiway to the left. However; it turned out that we had actually landed at flaps 20.To ensure task completion; such as verification of before landing checklist completion; I would; in the future; verify checklist status at the FAF and after landing clearance reception. Other than that; at the moment of suggestion that the flaps were not fully set; I would ask for verification of flap setting. Had that clarity been realized; a go around would have prevented the ASAP event. Executing a go around would have been the most prudent action; in hindsight.
In retrospect it is obvious that I allowed distraction of ATC communications to disrupt the Before Landing Checklist and the completion of the checklist. With the addition of fatigue factors I was more easily task saturated and needed to prioritize the completion of the checklist. Also; the Captain was probably similarly distracted and did not complete the tasks required for configuring the aircraft. Greater diligence in not allowing distractions to inhibit task completion.
B767-300 flight crew reported landing with Flaps 20 after being distracted with communications. Fatigue was also cited as a factor.