B767 flight crew reported momentary airspeed loss on approach due to windshear conditions.
Synopsis
B767 flight crew reported momentary airspeed loss on approach due to windshear conditions.
Narrative
While in the landing phase at approximately 100 ft. AGL I allowed the airspeed to decay to target airspeed minus approximately 17 kts. Prior to landing ZZZ Tower reported winds were 290 degrees at 27 gust 37 KIAS with LLWS in the area. This equated to a 34 kt. gusty crosswinds with a wintery mix of rain and snow. Preceding aircraft had reported gains of 15 KIAS below 100 ft. We had mitigated these risks by reviewing and briefing as a crew wind shear avoidance and go-around procedures as we transitioned to land at approximately 100 ft. the airspeed began to increase (as reported) and I retarded the throttles slightly then; almost instantaneously; the airspeed dropped rapidly from 156 KIAS to approximately 139 KIAS; although the First Officer (FO) (who was PM on the approach) remembers seeing as low as minus 20 kts. or 135 KIAS. They immediately called out 'Airspeed; Airspeed' which alerted me to the unexpected loss of airspeed. Now at around 40 ft. I added power to increase airspeed then; just as rapidly as the airspeed decayed; it returned to target plus approximately 3 KIAS. As the aircraft was now 20 ft. above the runway; on center line and in the TDZ so I elected to continue to land followed to an uneventful taxi to park. The entire event lasted less than 3 seconds and speaks to the high quality of the pilot group. The professional actions and inputs of the Relief Pilot's and FO (a new-hire and 2nd flight on the 767) were critical to a safe; caring; dependable and efficient completion of Aircraft X in this particularly dynamic environment..
Second reporter narrative
I was working Relief Pilot on approach into ZZZ with forecast chance of wind shear. This was a training flight with a new First Officer (FO); and we briefed extensively well before the top of descent; including all wind shear precautions (with an emphasis on cockpit indications of severe wind shear; i.e. unannunciated wind shear) and stabilized approach criteria. Line Check Airman (LCA) was Pilot flying (PF); and well-supported by excellent; highly-experienced new FO as PM. Saturated Approach Controller gave us a late turn on to localizer; cleared us for the approach; and Tower reported 'multiple reports of wind shear at 100 ft.; including plus 15 kts'. At approximately 150 ft.; we encountered a decreasing performance event of 15 kts.+ airspeed loss (NOT gain; as was reported by Tower); PM called 'airspeed; airspeed'; 'AIRSPEED LOW' EICAS appeared briefly; PF added appropriate power and landed uneventfully. In hindsight; there was no reactive 'Wind shear' warning; when there probably should have been with that level of decreasing performance and airspeed. The successful outcome in spite of these threats was the result of excellent leadership by the Captain; a very highly experienced and capable; well-trained and well-prepared new FO; a thoroughly briefed approach; and the highest degree of professionalism by the combined cockpit crew working together.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.