Narrative:

Taxi out and takeoff were normal. Climbout was VFR avoiding a line of weather. Intermediate level off at 360 was normal. We were cleared to FL400. At FL395 had an aural caution and an autopilot EICAS warning. At this point; as pilot not flying; I noticed the airspeed passing through 180 KTS on both sides (although I failed to check standby airspeed indicator) and announced (loudly) 'airspeed.' the captain acknowledged; pushed the throttles up and pushed the nose over. Ground speed indication was 340ish. Headwind indicated 140 KTS almost off the nose. Forecast was for only 40 KTS of headwind at FL400. The captain announced that we had an airspeed indication problem and an air data computer problem. My feeling was that the indications were all correct and that we needed to accelerate immediately. I called center and declared an emergency and asked them to verify my ground speed indication. At that point my ground speed was 365 KTS and ATC verified that as accurate. The captain was still thinking we were having air data computer problems and shallowed the descent and the airspeed began degrading past 190 KTS. At this point I physically put the throttles on the firewall and asked the captain to keep descending. I verified again with ATC that our ground speed was reading what theirs was showing. Leveled off at FL360 initially and then continued to FL340. The captain was asking to land nearest suitable; I felt that the aircraft was safe and stable and advocated continuing on to denver. After leveling at FL340 for a few minutes the captain began to trust the instrumentation again and the aircraft was returned to a normal status with the autopilot and auto throttle engaged. We canceled the emergency condition and proceeded on to den.

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Original NASA ASRS Text

Title: A B757-200 suffered an abrupt loss of airspeed when climbing to FL400. First Officer noted headwinds were much stronger than forecast.

Narrative: Taxi out and takeoff were normal. Climbout was VFR avoiding a line of weather. Intermediate level off at 360 was normal. We were cleared to FL400. At FL395 had an aural caution and an AUTOPILOT EICAS warning. At this point; as pilot not flying; I noticed the airspeed passing through 180 KTS on both sides (although I failed to check standby airspeed indicator) and announced (loudly) 'Airspeed.' The Captain acknowledged; pushed the throttles up and pushed the nose over. Ground speed indication was 340ish. Headwind indicated 140 KTS almost off the nose. Forecast was for only 40 KTS of headwind at FL400. The Captain announced that we had an airspeed indication problem and an air data computer problem. My feeling was that the indications were all correct and that we needed to accelerate immediately. I called Center and declared an emergency and asked them to verify my ground speed indication. At that point my ground speed was 365 KTS and ATC verified that as accurate. The Captain was still thinking we were having Air Data Computer problems and shallowed the descent and the airspeed began degrading past 190 KTS. At this point I physically put the throttles on the firewall and asked the Captain to keep descending. I verified again with ATC that our ground speed was reading what theirs was showing. Leveled off at FL360 initially and then continued to FL340. The Captain was asking to land nearest suitable; I felt that the aircraft was safe and stable and advocated continuing on to Denver. After leveling at FL340 for a few minutes the Captain began to trust the instrumentation again and the aircraft was returned to a normal status with the autopilot and auto throttle engaged. We canceled the emergency condition and proceeded on to DEN.

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.