<< >> NASA ASRS Report 298641, February 1995

Altitude deviation, autoplt operation aural altitude warning system failure with late crew intervention.

Attributes
ACN	298641
Time
Date	199502
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : jvl
State Reference	IL
Altitude	msl bound lower : 28400 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute airway : zau
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 14000 flight time type : 1000
ASRS Report	298641
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

While in descent from FL330 to FL290, at FL300 SOP call made by captain 'FL300 for FL290.' autoplt 'B' in command mode, INS FL290 set and selected. 'Altitude alert' light came on on captain's instrument panel, but no warning horn. No 'altitude alert' light illuminated on first officer's panel. At FL28.6, captain called out altitude and disengaged autoplt and initiated climb back to FL290, lowest altitude reached was FL28.4. ZAU inquired about our altitude at FL28.8. First officer continued balance of flight to ord. Subsequent trouble-shooting determined altitude select and hold functions of 'B' autoplt had failed along with warning horn and 'altitude alert' light on first officer's panel. Autoplt 'B' failed to capture set altitude. Entered defects in logbook for maintenance action.

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Original NASA ASRS Text

Title: ALTDEV, AUTOPLT OP AURAL ALT WARNING SYS FAILURE WITH LATE CREW INTERVENTION.

Narrative: WHILE IN DSCNT FROM FL330 TO FL290, AT FL300 SOP CALL MADE BY CAPT 'FL300 FOR FL290.' AUTOPLT 'B' IN COMMAND MODE, INS FL290 SET AND SELECTED. 'ALT ALERT' LIGHT CAME ON ON CAPT'S INSTRUMENT PANEL, BUT NO WARNING HORN. NO 'ALT ALERT' LIGHT ILLUMINATED ON FO'S PANEL. AT FL28.6, CAPT CALLED OUT ALT AND DISENGAGED AUTOPLT AND INITIATED CLB BACK TO FL290, LOWEST ALT REACHED WAS FL28.4. ZAU INQUIRED ABOUT OUR ALT AT FL28.8. FO CONTINUED BAL OF FLT TO ORD. SUBSEQUENT TROUBLE-SHOOTING DETERMINED ALT SELECT AND HOLD FUNCTIONS OF 'B' AUTOPLT HAD FAILED ALONG WITH WARNING HORN AND 'ALT ALERT' LIGHT ON FO'S PANEL. AUTOPLT 'B' FAILED TO CAPTURE SET ALT. ENTERED DEFECTS IN LOGBOOK FOR MAINT ACTION.

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.