<< >> NASA ASRS Report 200514, December 1991

Airspeed deviation while air carrier medium large transport is on autoplt and automatic thrust senses a speed decrease command through the FMC system.

Attributes
ACN	200514
Time
Date	199112
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zab
State Reference	NM
Altitude	msl bound lower : 37000 msl bound upper : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
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 : commercial pilot : cfi pilot : atp pilot : instrument
Experience	flight time last 90 days : 230 flight time total : 9500 flight time type : 510
ASRS Report	200514
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Climbing to FL370, autoplt #2 and autothrust system engaged and active. Level off maneuver was normal, however, speed bug rapidly (approximately 1 second) decreased from approximately .755 mach to below predicted stall. Autothrust system reduced engine power to idle. No ECAM warning or messages appeared. PF deselected managed speed to selected speed and then immediately reselected managed speed. Target airspeed immediately returned to normal (approximately .75 M) and autothrust responded normally. Total anomaly and restoration to normal function took less than 10 seconds and less than 10 KTS of airspeed were lost during the power reduction to idle. Maintenance notified at destination. No failures discovered.

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Original NASA ASRS Text

Title: AIRSPD DEV WHILE ACR MLG IS ON AUTOPLT AND AUTO THRUST SENSES A SPD DECREASE COMMAND THROUGH THE FMC SYS.

Narrative: CLBING TO FL370, AUTOPLT #2 AND AUTOTHRUST SYS ENGAGED AND ACTIVE. LEVEL OFF MANEUVER WAS NORMAL, HOWEVER, SPD BUG RAPIDLY (APPROX 1 SECOND) DECREASED FROM APPROX .755 MACH TO BELOW PREDICTED STALL. AUTOTHRUST SYS REDUCED ENG PWR TO IDLE. NO ECAM WARNING OR MESSAGES APPEARED. PF DESELECTED MANAGED SPD TO SELECTED SPD AND THEN IMMEDIATELY RESELECTED MANAGED SPD. TARGET AIRSPD IMMEDIATELY RETURNED TO NORMAL (APPROX .75 M) AND AUTOTHRUST RESPONDED NORMALLY. TOTAL ANOMALY AND RESTORATION TO NORMAL FUNCTION TOOK LESS THAN 10 SECONDS AND LESS THAN 10 KTS OF AIRSPD WERE LOST DURING THE PWR REDUCTION TO IDLE. MAINT NOTIFIED AT DEST. NO FAILURES DISCOVERED.

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.