Flight crew deviation from ATC clearance in speed deviation. Automatic throttle system failure. Crew...

Attributes
ACN	276142
Time
Date	199407
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ztl
State Reference	GA
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	L-1011-500 Series
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 10000
ASRS Report	276142
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 21000
ASRS Report	276139
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other anomaly other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

I was the first officer on flight atl-lgw. We were cruising at FL330 between spa and gso. It was the captain's leg and he was doing the required navigation accuracy checks for an oceanic crossing. I was filling in the flight log and the so was working on the fuel chart. The L-1011-500 we were flying had the performance management system which was in use, giving commands to the automatic throttle system indicating .83 mach. Apparently the performance management system started commanding bad input to the automatic throttles. Instead of disconnecting and giving some kind of warning, the automatic throttle system responded by reducing the throttles to idle thrust. With no warning or indications of anything abnormal, the airspeed apparently decayed about 40 KTS low. Observing the low airspeed the captain immediately shoved the throttles forward and called for a lower altitude in an attempt to regain the airspeed. I called ATC and asked for FL310 immediately. The captain had some difficulty disconnecting the automatic throttle system and had to fight the throttles momentarily. We were given FL310 by ATC and regained the airspeed during the descent. After everything appeared to be working normal again, we requested and received FL330 and climbed back up without incident. Later in-flight the performance management system and automatic throttle system again malfunctioned and we discontinued the use of the authority/authorized throttle system. The appropriate logbook entries were recorded.

Original NASA ASRS Text

Title: FLC DEV FROM ATC CLRNC IN SPD DEV. AUTO THROTTLE SYS FAILURE. CREW EXPERIENCED DIFFICULTY IN THE DISCONNECT OF THE AUTO THROTTLE SYS.

Narrative: I WAS THE FO ON FLT ATL-LGW. WE WERE CRUISING AT FL330 BTWN SPA AND GSO. IT WAS THE CAPT'S LEG AND HE WAS DOING THE REQUIRED NAV ACCURACY CHKS FOR AN OCEANIC XING. I WAS FILLING IN THE FLT LOG AND THE SO WAS WORKING ON THE FUEL CHART. THE L-1011-500 WE WERE FLYING HAD THE PERFORMANCE MGMNT SYS WHICH WAS IN USE, GIVING COMMANDS TO THE AUTO THROTTLE SYS INDICATING .83 MACH. APPARENTLY THE PERFORMANCE MGMNT SYS STARTED COMMANDING BAD INPUT TO THE AUTO THROTTLES. INSTEAD OF DISCONNECTING AND GIVING SOME KIND OF WARNING, THE AUTO THROTTLE SYS RESPONDED BY REDUCING THE THROTTLES TO IDLE THRUST. WITH NO WARNING OR INDICATIONS OF ANYTHING ABNORMAL, THE AIRSPD APPARENTLY DECAYED ABOUT 40 KTS LOW. OBSERVING THE LOW AIRSPD THE CAPT IMMEDIATELY SHOVED THE THROTTLES FORWARD AND CALLED FOR A LOWER ALT IN AN ATTEMPT TO REGAIN THE AIRSPD. I CALLED ATC AND ASKED FOR FL310 IMMEDIATELY. THE CAPT HAD SOME DIFFICULTY DISCONNECTING THE AUTO THROTTLE SYS AND HAD TO FIGHT THE THROTTLES MOMENTARILY. WE WERE GIVEN FL310 BY ATC AND REGAINED THE AIRSPD DURING THE DSCNT. AFTER EVERYTHING APPEARED TO BE WORKING NORMAL AGAIN, WE REQUESTED AND RECEIVED FL330 AND CLBED BACK UP WITHOUT INCIDENT. LATER INFLT THE PERFORMANCE MGMNT SYS AND AUTO THROTTLE SYS AGAIN MALFUNCTIONED AND WE DISCONTINUED THE USE OF THE AUTH THROTTLE SYS. THE APPROPRIATE LOGBOOK ENTRIES WERE RECORDED.

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.

Flight crew deviation from ATC clearance in speed deviation. Automatic throttle system failure. Crew experienced difficulty in the disconnect of the automatic throttle system.