B737-700
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented; General Maintenance Action
Human Factors; Aircraft; Weather
We were on final into DEN (16L) and cleared to land. There were some rain shafts on the final approach course that generated turbulence as well as airspeed fluctuations (plus/minus 15 to 20 KTS). We were fully configured and stabilized well before 1;000 FT AGL. After passing the FAF; I could feel the pitch increase and airspeed started dropping. It took what felt like 80% full throttle to maintain my target speed of 151 KTS. Then; the airspeed rapidly increased to 170 KTS and we oversped the flaps 30 configuration. Concerned about the overspeed; I called for a flap retraction. At about 800 FT; we were back in stable/smooth air. The First Officer did suggest a go-around; however; I decided to land. My biggest concern was having to circle around and fly through that same weather again. We reconfigured to flaps 30 and landed without any further incident. At no time did we ever get a windshear warning.In retrospect; I believe that my mistake was calling for a flap retraction below 1;000 without initiating a go-around. I focused on the flap overspeed issue and tried to resolve that while continuing the approach. I went from a stable approach to an unstable approach and failed to make the right decision to go-around. The whole event probably took less than one minute. I think that some of the factors that weighed on me and contributed to this wrong decision were the gusty winds and turbulent conditions. At the time; I believed the safer course of action was to land; even though I was not stable until approximately 800 AGL than to have to circle around and try to fly through the turbulence and gust a second time. I was wrong!
Shooting the visual to 16L; we encountered virga and light turbulence. We were stabilized by 1;000 FT AGL but not long after that the wind shifted dramatically; it felt like we were sinking; and the pilot flying added a large amount of thrust to arrest the sink rate. There were no windshear warnings from the plane; only the airspeed drop and thrust lever angle. Just as that happened; I noticed the airspeed increase into the red band; up to 170 KTS (5-KT overspeed) and called it out. Ref and target were 131 and 151 for a flaps 30 approach due to gusty conditions. Placard speed is 165. Pilot flying said 'bring them up' which I assumed meant to bring the flaps up before the overspeed got worse and we caused damage; and also assumed this meant we would go-around. I brought the flaps to 15 and; after a few seconds; airspeed started to come back down. We were still on glideslope with a descent rate of less than 1;000 FPM. Since we were no longer configured for landing; and thus; unstable below 1;000 FT; I recommended a go-around. The pilot flying said; 'let's land' and called for flaps 30. As with the call to retract flaps; there wasn't a lot of time to discuss. I saw that we were on speed and stable and decided to comply with the pilot flying's instruction since I believed we could still safely land and thought he may have some reason he thought this was a better decision. There wasn't time to discuss and I was hesitant to override him. We appeared safe to land by resetting the flaps so I did what I was told. Afterward; we talked about it and agreed that we probably should have left the flaps set at 30 and continued; or gone around since we were greater than target +10; or gone around once we were no longer configured below 1;000 FT. In the moment; we were doing the best we could with limited time to communicate; and did the best we could. In hindsight; after calling for the go-around I should have left the flaps at 15 instead of resetting landing flaps as instructed; and called for the go-around again.In the moment; I made the best decision I could with what little information I had. Our windshear training usually doesn't have us landing with a target speed so close to overspeed. Maintenance says flap overspeeds in that kind of weather are common there. If that's the case; maybe a [heads-up] circular to all pilots discussing flap overspeeds due to high target speed and gusty conditions on final would help crews mentally prepare for what they will do in a situation they may not have thought about before. Without an audible windshear alert; my gut reaction wasn't that we were in windshear. In the simulator for training; we usually push well past our comfort zone and into the shaker before we execute the escape maneuver. From the side lines; it's easy to say we should have just gone around. In the moment though; in the real world; it was a little greyer.
B737-700 flight crew encounters turbulence and windshear during approach resulting in a flap overspeed but no windshear warning. The Captain calls for the flaps to be raised to 15 initially and when clear of the virga flaps 30 are called for again (below 1;000 FT) and the approach continues to landing.