Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Time Pressure
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control; Flight Crew Took Evasive Action
Weather
Windshear and power lever over-travel event. Route of flight was from the north into Boise. There had been occasional light chop along the way; coinciding with the tops and bases of the different cloud layers. This happened on the RNAV (RNP) Z 10L approach into Boise via the LIBYY transition. We were night VMC from LIBYY on. There was a scattered layer of clouds over the Boise airport about 4500 feet AFE. Reported wind was 120/7. We had ice on the wings and REF SPEEDS INCR selected; but it was 6 degrees Celsius at Boise.Sequence of events; as best remembered: Airspeed was moving between 200 and 205 on the VPATH approaching CAMML; which is 9 miles from the runway; and almost 3000 feet AFE. Airspeed jumped very quickly. Power was retarded to flight idle as airspeed approached the high speed redline for flaps zero. The power reduction wasn't enough; so VS was pushed and rolled to less of a descent rate; maybe 200 feet per minute. The speed still wasn't slowing; so the autopilot was disengaged and a level flight pitch was added. Maximum airspeed reached was a few knots below redline before the airspeed was under control and moving toward 200 again. Approaching SEPRE (5.3 miles from the runway) there was a rapid reversal of the airspeed; and it required a pitch down and huge power input to keep the airspeed from dropping into the red stickshaker region. Minimum airspeed reached was 2 kts. above the low speed redline; and for just a few seconds. Later; after the flight; it was noted that the power levers had slipped marginally beyond the rating detent for a second. We had overshot the centerline for 10L and were lined up for 10R. There was no traffic conflict with other aircraft. The wind seemed steady at that point. We had flown out of the windshear by the time we turned final; and a return to the centerline of 10L was made by using gentle banking. A smooth landing was made. Maintenance was notified about the power lever over-travel and windshear event. Dispatch was also notified. The maintenance inspection and diagnostic code retrieval delayed the next flight about 20 extra minutes.Later; we talked with Boise Tower. He told us that when we were on approach to the airport that the west end (where we were on the approach to 10L) winds were directionally 220 V 340 gusting to 30 knots. He also said that the east end winds had been 70 V 190 gusting to 24. This had not been previously reported. There were indications for a missed approach; from the big airspeed swings to lining up on the incorrect close parallel runway. Why not go missed approach? We both considered it after the final approach fix. Perhaps the VMC conditions and the eventual smoothness above 1000 feet AFE gave us a 'Can Do' bias. We decided that to land was safe after the windshear had subsided. When we debriefed later; we discussed how fast the airspeed had changed when pitch; power; airspeed; glidepath had been mostly steady. The increased groundspeed at the beginning of the event took away more distance and time than we had initially perceived in flight. I kept thinking that this was a momentary deviation from a stabilized approach; and it appeared to be that as we made corrections along the way. These events hit so hard and fast; and you try to follow the proper procedures as best you can. Just keep reviewing and studying your procedures. Try to be as methodical as you can.
[Report narrative contained no additional information.]
Air Carrier Captain reported power lever over travel event while executing windshear maneuver and resulted in an overspeed condition.