Narrative:

FL370, mach .83, autoplt on, autothrottles-thrust management on, cruise flight had been established approximately 1 hour. The copilot suddenly stated, 'check airspeed.' airspeed was 220 KTS and decreasing. Copilot advanced throttles some. I disconnected autoplt and autothrottles. Took control of aircraft, advanced power, called for mct, lowered the nose to the horizon (normal cruise in widebody transport is 3 1/2 degrees nose up) and started a descent. Copilot canned moncton center for lower altitude. Cleared to FL290. As airspeed increased to approximately 260 KTS, mach .82. Leveled at FL350 and requested FL330 as a final. After stabilized cruise at FL330, returned autoplt, autothrottles on, operation normal. It is not known what the power was at the time of the incident, as we immediately advanced power. However, after discussion we feel the throttles were approximately 12 O'clock, straight up. FMS was set for mach .835. The F/east had checked the engine INS several moments before the incident and everything was normal. I put the following write-up in the log book: 'at 37000 autothrottles retarded--observed a.south. 250 KTS--went mct--descended 2000' to 350, operation normal with autothrottles and T.M. For last 30 mins of flight.'

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Original NASA ASRS Text

Title: AFTER BEING STABILIZED AT CRUISE FOR OVER AN HOUR, FLT CREW NOTICED AIRSPEED DECREASING. ADVANCED POWER LEVERS AND DESCENDED TO REGAIN AIRSPEED. STABILIZED AGAIN AT FL330.

Narrative: FL370, MACH .83, AUTOPLT ON, AUTOTHROTTLES-THRUST MGMNT ON, CRUISE FLT HAD BEEN ESTABLISHED APPROX 1 HR. THE COPLT SUDDENLY STATED, 'CHK AIRSPD.' AIRSPD WAS 220 KTS AND DECREASING. COPLT ADVANCED THROTTLES SOME. I DISCONNECTED AUTOPLT AND AUTOTHROTTLES. TOOK CTL OF ACFT, ADVANCED PWR, CALLED FOR MCT, LOWERED THE NOSE TO THE HORIZON (NORMAL CRUISE IN WDB IS 3 1/2 DEGS NOSE UP) AND STARTED A DSNT. COPLT CANNED MONCTON CENTER FOR LOWER ALT. CLRED TO FL290. AS AIRSPD INCREASED TO APPROX 260 KTS, MACH .82. LEVELED AT FL350 AND REQUESTED FL330 AS A FINAL. AFTER STABILIZED CRUISE AT FL330, RETURNED AUTOPLT, AUTOTHROTTLES ON, OPERATION NORMAL. IT IS NOT KNOWN WHAT THE PWR WAS AT THE TIME OF THE INCIDENT, AS WE IMMEDIATELY ADVANCED PWR. HOWEVER, AFTER DISCUSSION WE FEEL THE THROTTLES WERE APPROX 12 O'CLOCK, STRAIGHT UP. FMS WAS SET FOR MACH .835. THE F/E HAD CHKED THE ENG INS SEVERAL MOMENTS BEFORE THE INCIDENT AND EVERYTHING WAS NORMAL. I PUT THE FOLLOWING WRITE-UP IN THE LOG BOOK: 'AT 37000 AUTOTHROTTLES RETARDED--OBSERVED A.S. 250 KTS--WENT MCT--DSNDED 2000' TO 350, OPERATION NORMAL WITH AUTOTHROTTLES AND T.M. FOR LAST 30 MINS OF FLT.'

Data retrieved from NASA's ASRS site as of July 2007 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.