<< >> NASA ASRS Report 170297, February 1991

Large transport lost air data computer. Switching to operative equipment. Flight crew excursioned 500' off assigned altitude.

Attributes
ACN	170297
Time
Date	199102
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : aex
State Reference	LA
Altitude	msl bound lower : 35000 msl bound upper : 35500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zhu tracon : lax
Operator	common carrier : air carrier
Make Model Name	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 : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 60 flight time total : 10000 flight time type : 4000
ASRS Report	170297
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 150 flight time total : 8900 flight time type : 130
ASRS Report	170305
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance
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:

On autoplt #1 navigation mode (omega) selected. #1 central air data system malfunctioned. Lost captain airspeed, altimeter, vertical speed, autothrottle, autoplt, and the associated instrument (including altitude reporting). Flew on standby instrument and selected #2 autoplt and captain auxiliary CADC. Aircraft deviated 500' during process. Notified ATC. They stated there was no problem.

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Original NASA ASRS Text

Title: LGT LOST AIR DATA COMPUTER. SWITCHING TO OPERATIVE EQUIPMENT. FLT CREW EXCURSIONED 500' OFF ASSIGNED ALT.

Narrative: ON AUTOPLT #1 NAV MODE (OMEGA) SELECTED. #1 CENTRAL AIR DATA SYS MALFUNCTIONED. LOST CAPT AIRSPD, ALTIMETER, VERT SPD, AUTOTHROTTLE, AUTOPLT, AND THE ASSOCIATED INSTRUMENT (INCLUDING ALT RPTING). FLEW ON STANDBY INSTRUMENT AND SELECTED #2 AUTOPLT AND CAPT AUX CADC. ACFT DEVIATED 500' DURING PROCESS. NOTIFIED ATC. THEY STATED THERE WAS NO PROB.

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.