B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 138; Flight Crew Type 964
Situational Awareness; Confusion; Distraction; Workload
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Aircraft Equipment Problem Dissipated; Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory; Flight Crew FLC Overrode Automation
Aircraft; Procedure; Weather
On approach to Runway XXL; the airport was experiencing high and gusty winds; last called 220/22G33; we configured at the final approach fix at setting flaps 30 with accompanying green light at approximately 1;200 feet AGL. Autothrottles and autopilot were engaged. Passing through 1;000 feet; we got a good gust wind/airspeed increase to approximately 178-180 KIAS. This must have activated the flap blowback feature and it pushed the flaps back to approximately 26 degrees. At that point; I took the aircraft and disconnected the autopilot and autothrottles. I did not notice the flaps had been pushed back and continued to fly the approach. Passing through 200 feet we received the too low terrain warning. I verbally confirmed visual with the First Officer and continued the approach. Upon receiving the aural warning a third time at approximately 50 feet; First Officer noted the abnormal flap setting. The airplane was easily controllable and I had already started to flare; so I landed with 26 degrees final flap setting and taxied uneventfully from the landing runway to the gate. During taxi; we reset the flaps to 25 and then 30 degrees and the flaps worked normally; without issue.
Airspeed correction due to steady state headwind plus gust was 19 KTS. Approach target speed approximately 164 KIAS (flap 30 approach/flap 30 speed 175 placard). Airspeed on approach was observed during FO crosscheck consistently above target but within stable criteria. At approximately 100-200 feet AGL GPWS 'too low' warning sounded. FO crosscheck analysis picked up flap setting at 30 degrees/25 degrees on indicator. Aircraft was approaching threshold stable on normal glide path. FO incorrectly verbalized 'flaps asymmetry' as the words 'trailing edge flap disagree' did not come to my mouth at the time. Captain elected to continue to land as we were now initiating flare.Following landing crew discussed potential that as airspeed was near flap placard limit it was possible that a gust resulted in activation of flap load limiter following full extension on approach resulting in flap blowback to 25 degrees. Clearing runway Captain had FO set flaps up one notch back to 30 which alleviated condition in accordance with trailing edge flap disagree checklist.
A B737 encountered 19 knot gusts on short final which caused a flap blow up from 30 to 25. The EGPWS TOO LOW alert sounded but the First Officer thought flap asymmetry. After landing the flaps were cycled with normal results.