B767-300 throttles retarded without the flight crew's awareness. The airspeed decreased; stick shake...

Attributes
ACN	755370
Time
Date	200709
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : sbbs.artcc
State Reference	FO
Altitude	msl single value : 30000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : sbbs.artcc
Operator	common carrier : air carrier
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	755370
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	755366
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly
Independent Detector	other flight crewa other flight crewb other other : 3
Resolutory Action	flight crew : regained aircraft control flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

Shortly after the top of climb at FL300; the stick shaker activated. At first; I thought that it might be an erroneous activation; because the aircraft attitude looked normal; we were in level flight; and I had not noticed any change in aircraft wind noise; pitch angle; or trim. I noted that my airspeed was approximately 220 KIAS. I called out to the first officer; who was PF; that it might be a false stick shaker. I then noted his airspeed; which was also very low. I called out lower the nose; but by this time he had already advanced the throttles; disconnected the autoplt and begun a descent. We also had inoperative eec's to consider. I informed brasilia center of the situation; and they cleared us into airspace from 280 to 300. We regained airspeed and returned to normal cruise. Our lowest altitude was approximately 28700 ft. As we were discussing what might have happened; the autothrottles started to pull the throttles back for no reason. At this point; we disconnected them. This aircraft had a recent history of autothrottle malfunctions; most of which described uncommanded disconnect. However; there was one describing an autothrottle malfunction like we had; but I was not aware of it because it was further back than I had reviewed. I am guessing that the autothrottles had retarded from climb to a below cruise power setting; and in the dark we did not detect the throttle position. At about this time; I was preparing my charts for position reports; and the first officer was editing the FMS. Although I always attempt to make sure only 1 pilot is heads down at a time; I cannot say for sure what happened in this case. In retrospect; I probably should not have accepted this trip; which started out in ZZZ1 and required me to deadhead on very short notice to ZZZ2 and fly the all-nighter to sbgl. I was awake for almost 30 hours; followed by a 34 hour layover and another all-nighter; during which this event happened. Obviously; I was not performing at my best.

Original NASA ASRS Text

Title: B767-300 THROTTLES RETARDED WITHOUT THE FLT CREW'S AWARENESS. THE AIRSPEED DECREASED; STICK SHAKER ACTIVATED; AND THE ACFT LOST APPROX 1300 FT WHILE AIRSPEED WAS REGAINED.

Narrative: SHORTLY AFTER THE TOP OF CLB AT FL300; THE STICK SHAKER ACTIVATED. AT FIRST; I THOUGHT THAT IT MIGHT BE AN ERRONEOUS ACTIVATION; BECAUSE THE ACFT ATTITUDE LOOKED NORMAL; WE WERE IN LEVEL FLT; AND I HAD NOT NOTICED ANY CHANGE IN ACFT WIND NOISE; PITCH ANGLE; OR TRIM. I NOTED THAT MY AIRSPD WAS APPROX 220 KIAS. I CALLED OUT TO THE FO; WHO WAS PF; THAT IT MIGHT BE A FALSE STICK SHAKER. I THEN NOTED HIS AIRSPD; WHICH WAS ALSO VERY LOW. I CALLED OUT LOWER THE NOSE; BUT BY THIS TIME HE HAD ALREADY ADVANCED THE THROTTLES; DISCONNECTED THE AUTOPLT AND BEGUN A DSCNT. WE ALSO HAD INOP EEC'S TO CONSIDER. I INFORMED BRASILIA CTR OF THE SITUATION; AND THEY CLRED US INTO AIRSPACE FROM 280 TO 300. WE REGAINED AIRSPD AND RETURNED TO NORMAL CRUISE. OUR LOWEST ALT WAS APPROX 28700 FT. AS WE WERE DISCUSSING WHAT MIGHT HAVE HAPPENED; THE AUTOTHROTTLES STARTED TO PULL THE THROTTLES BACK FOR NO REASON. AT THIS POINT; WE DISCONNECTED THEM. THIS ACFT HAD A RECENT HISTORY OF AUTOTHROTTLE MALFUNCTIONS; MOST OF WHICH DESCRIBED UNCOMMANDED DISCONNECT. HOWEVER; THERE WAS ONE DESCRIBING AN AUTOTHROTTLE MALFUNCTION LIKE WE HAD; BUT I WAS NOT AWARE OF IT BECAUSE IT WAS FURTHER BACK THAN I HAD REVIEWED. I AM GUESSING THAT THE AUTOTHROTTLES HAD RETARDED FROM CLB TO A BELOW CRUISE PWR SETTING; AND IN THE DARK WE DID NOT DETECT THE THROTTLE POS. AT ABOUT THIS TIME; I WAS PREPARING MY CHARTS FOR POS RPTS; AND THE FO WAS EDITING THE FMS. ALTHOUGH I ALWAYS ATTEMPT TO MAKE SURE ONLY 1 PLT IS HEADS DOWN AT A TIME; I CANNOT SAY FOR SURE WHAT HAPPENED IN THIS CASE. IN RETROSPECT; I PROBABLY SHOULD NOT HAVE ACCEPTED THIS TRIP; WHICH STARTED OUT IN ZZZ1 AND REQUIRED ME TO DEADHEAD ON VERY SHORT NOTICE TO ZZZ2 AND FLY THE ALL-NIGHTER TO SBGL. I WAS AWAKE FOR ALMOST 30 HRS; FOLLOWED BY A 34 HR LAYOVER AND ANOTHER ALL-NIGHTER; DURING WHICH THIS EVENT HAPPENED. OBVIOUSLY; I WAS NOT PERFORMING AT MY BEST.

Data retrieved from NASA's ASRS site as of January 2009 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.

B767-300 throttles retarded without the flight crew's awareness. The airspeed decreased; stick shaker activated; and the aircraft lost approximately 1300 ft while airspeed was regained.