Narrative:

We were cruising at FL410. Everything appeared normal when there seemed to be a rapid loss of airspeed and we noticed a slight burble. The first officer, PF, noticed the airspeed was around 190 KTS and he firewalled the throttles. When the airspeed did not rise promptly, he started a slight descent. When passing FL403 and 800 FPM we notified center what we were doing. They cleared us to FL390 and then down to FL370. At FL390 we had normal airspeed back. At no time was the aircraft out of control. When all system seemed to be working normal and having double-checked our weight we requested clearance back to FL410. It must have been an autothrottle system problem and/or also a sinking air mass. Had no further problems but had maintenance check the autothrottle system at jfk. Supplemental information from acn 319668: the captain's leadership, crew coordination and team building was a large help in dealing with this occurrence. In his initial briefing and subsequent actions, the captain made it very clear that the PF was in charge of the aircraft on their leg and never micro-managed the flying from the left seat. Because of his command style, I did not hesitate to begin the corrective actions, even though we both discovered the problem at about the same time. Since I was the PF, I took control of the aircraft assuming that if the captain wanted to take subsequent control, he would announce his intentions and do so. We had worked together for the balance of the month and had a good idea of what each expected of the other. This allowed each to anticipate the needs and requirements of each other without excessive verbal communication. With all the cautions and alerts on the B757/76 aircraft, one would think there would be a low airspeed caution alert for just such an occurrence, but the speed command in the ADI changing color to amber and flashing is the only low speed warning, before the stick shaker and stall warning activate.

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Original NASA ASRS Text

Title: FLC OF B757 HAS LOSS OF AIRSPD AND UNABLE TO MAINTAIN ALT.

Narrative: WE WERE CRUISING AT FL410. EVERYTHING APPEARED NORMAL WHEN THERE SEEMED TO BE A RAPID LOSS OF AIRSPD AND WE NOTICED A SLIGHT BURBLE. THE FO, PF, NOTICED THE AIRSPD WAS AROUND 190 KTS AND HE FIREWALLED THE THROTTLES. WHEN THE AIRSPD DID NOT RISE PROMPTLY, HE STARTED A SLIGHT DSCNT. WHEN PASSING FL403 AND 800 FPM WE NOTIFIED CTR WHAT WE WERE DOING. THEY CLRED US TO FL390 AND THEN DOWN TO FL370. AT FL390 WE HAD NORMAL AIRSPD BACK. AT NO TIME WAS THE ACFT OUT OF CTL. WHEN ALL SYS SEEMED TO BE WORKING NORMAL AND HAVING DOUBLE-CHKED OUR WT WE REQUESTED CLRNC BACK TO FL410. IT MUST HAVE BEEN AN AUTOTHROTTLE SYS PROB AND/OR ALSO A SINKING AIR MASS. HAD NO FURTHER PROBS BUT HAD MAINT CHK THE AUTOTHROTTLE SYS AT JFK. SUPPLEMENTAL INFO FROM ACN 319668: THE CAPT'S LEADERSHIP, CREW COORD AND TEAM BUILDING WAS A LARGE HELP IN DEALING WITH THIS OCCURRENCE. IN HIS INITIAL BRIEFING AND SUBSEQUENT ACTIONS, THE CAPT MADE IT VERY CLR THAT THE PF WAS IN CHARGE OF THE ACFT ON THEIR LEG AND NEVER MICRO-MANAGED THE FLYING FROM THE L SEAT. BECAUSE OF HIS COMMAND STYLE, I DID NOT HESITATE TO BEGIN THE CORRECTIVE ACTIONS, EVEN THOUGH WE BOTH DISCOVERED THE PROB AT ABOUT THE SAME TIME. SINCE I WAS THE PF, I TOOK CTL OF THE ACFT ASSUMING THAT IF THE CAPT WANTED TO TAKE SUBSEQUENT CTL, HE WOULD ANNOUNCE HIS INTENTIONS AND DO SO. WE HAD WORKED TOGETHER FOR THE BALANCE OF THE MONTH AND HAD A GOOD IDEA OF WHAT EACH EXPECTED OF THE OTHER. THIS ALLOWED EACH TO ANTICIPATE THE NEEDS AND REQUIREMENTS OF EACH OTHER WITHOUT EXCESSIVE VERBAL COM. WITH ALL THE CAUTIONS AND ALERTS ON THE B757/76 ACFT, ONE WOULD THINK THERE WOULD BE A LOW AIRSPD CAUTION ALERT FOR JUST SUCH AN OCCURRENCE, BUT THE SPD COMMAND IN THE ADI CHANGING COLOR TO AMBER AND FLASHING IS THE ONLY LOW SPD WARNING, BEFORE THE STICK SHAKER AND STALL WARNING ACTIVATE.

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.