A B737-800 crossed a convective frontal boundary and after the tailwind increased to 105 kts the air...

Attributes
ACN	975507
Time
Date	201110
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Autothrottle/Speed Control
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying First Officer
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

Copilot's leg. Takeoff and departure uneventful. At FL390; line of weather extending from our departure airport northeast with lots of convective activity. Our flight was on top of all weather. After crossing the frontal boundary and without notice; winds increased to 105 knots out of the west (strong tailwind) and airspeed surged to about 5-10 knots into the red band (overspeed) and clacker sounded. Throttles manually retarded to 70% N1 and airspeed reduced back toward .78M but continued a slow decrease without any automatic addition of thrust from either engine toward selected mach. Thrust then manually added to selected cruise 'climb' setting (green carrot on N1 gauge) and engines did not respond. In addition; airspeed continued to slowly decrease. After about 10 seconds; captain selected engine anti-ice on and after approximately 5 seconds the thrust from both engines responded as selected. Both events; airframe overspeed and lack of response with autothrottles engaged; were recorded in aircraft maintenance logbook and a thorough discussion with maintenance upon arrival.

Original NASA ASRS Text

Title: A B737-800 crossed a convective frontal boundary and after the tailwind increased to 105 kts the airspeed decreased to MACH .74; then oversped before returning to .78. But the airspeed then bled off until the crew intervened to increase N1.

Narrative: Copilot's leg. Takeoff and departure uneventful. At FL390; line of weather extending from our departure airport northeast with lots of convective activity. Our flight was on top of all weather. After crossing the frontal boundary and without notice; winds increased to 105 knots out of the west (strong tailwind) and airspeed surged to about 5-10 knots into the red band (overspeed) and clacker sounded. Throttles manually retarded to 70% N1 and airspeed reduced back toward .78M but continued a slow decrease without any automatic addition of thrust from either engine toward selected Mach. Thrust then manually added to selected cruise 'CLB' setting (green carrot on N1 gauge) and engines did not respond. In addition; airspeed continued to slowly decrease. After about 10 seconds; Captain selected engine Anti-ice ON and after approximately 5 seconds the thrust from both engines responded as selected. Both events; airframe overspeed and lack of response with autothrottles engaged; were recorded in aircraft maintenance logbook and a thorough discussion with Maintenance upon arrival.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

A B737-800 crossed a convective frontal boundary and after the tailwind increased to 105 kts the airspeed decreased to mach .74; then oversped before returning to .78. But the airspeed then bled off until the crew intervened to increase N1.