Altitude deviation. First officer flying using #2 air data computer and autoplt, air data computer failed, aircraft climbed 800 ft before flight crew disconnected autoplt and returned to assigned altitude.

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Attributes
ACN	331150
Time
Date	199603
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zdv
State Reference	CO
Altitude	msl bound lower : 33000 msl bound upper : 33800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
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 : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 16000 flight time type : 1900
ASRS Report	331150
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 4800 flight time type : 870
ASRS Report	331307
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

After experiencing an air data computer failure #2 and setting source select knob to #1 and transferring autoplt to flight data 1 the air data computer reset showing normal indications. So we switched back to normal on the source select then transferred the autoplt flight director back to #2 after 15 seconds or so, just long enough to be satisfied it would be ok and look away. The air data computer #2 failed again and the nose pitched up gaining 700-800 ft before the autoplt was disconnected and altitude reestablished.

Original NASA ASRS Text

Title: ALTDEV. FO FLYING USING #2 AIR DATA COMPUTER AND AUTOPLT, ADC FAILED, ACFT CLBED 800 FT BEFORE FLC DISCONNECTED AUTOPLT AND RETURNED TO ASSIGNED ALT.

Narrative: AFTER EXPERIENCING AN AIR DATA COMPUTER FAILURE #2 AND SETTING SOURCE SELECT KNOB TO #1 AND TRANSFERRING AUTOPLT TO FLT DATA 1 THE AIR DATA COMPUTER RESET SHOWING NORMAL INDICATIONS. SO WE SWITCHED BACK TO NORMAL ON THE SOURCE SELECT THEN TRANSFERRED THE AUTOPLT FLT DIRECTOR BACK TO #2 AFTER 15 SECONDS OR SO, JUST LONG ENOUGH TO BE SATISFIED IT WOULD BE OK AND LOOK AWAY. THE AIR DATA COMPUTER #2 FAILED AGAIN AND THE NOSE PITCHED UP GAINING 700-800 FT BEFORE THE AUTOPLT WAS DISCONNECTED AND ALT REESTABLISHED.

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.