<< >> NASA ASRS Report 480020, July 2000

A falcon 50 in cruise at FL370 experienced an altitude excursion caused by the autoplt altitude hold mode malfunction.

Attributes
ACN	480020
Time
Date	200007
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : las.vortac
Altitude	msl single value : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc
Operator	general aviation : corporate
Make Model Name	Falcon 50
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute airway : j76.airway
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 100 flight time total : 7300 flight time type : 2400
ASRS Report	480020
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : company policies other anomaly
Independent Detector	aircraft equipment other aircraft equipment : altitude warning horn
Resolutory Action	flight crew : regained aircraft control
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

While in cruise at FL370, we were both performing routine duties with autoplt and altitude hold on. We both heard the altitude alerter and noticed the aircraft had climbed to FL374. We disengaged the autoplt and leveled the aircraft at FL370. ZLA said nothing. It is important for pilots not to completely trust the autoplt and for 1 pilot to monitor the flight instruments. Also it might help if altitude alerters sounded at +/-100 ft instead of +/-300 ft.

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Original NASA ASRS Text

Title: A FALCON 50 IN CRUISE AT FL370 EXPERIENCED AN ALT EXCURSION CAUSED BY THE AUTOPLT ALT HOLD MODE MALFUNCTION.

Narrative: WHILE IN CRUISE AT FL370, WE WERE BOTH PERFORMING ROUTINE DUTIES WITH AUTOPLT AND ALT HOLD ON. WE BOTH HEARD THE ALT ALERTER AND NOTICED THE ACFT HAD CLBED TO FL374. WE DISENGAGED THE AUTOPLT AND LEVELED THE ACFT AT FL370. ZLA SAID NOTHING. IT IS IMPORTANT FOR PLTS NOT TO COMPLETELY TRUST THE AUTOPLT AND FOR 1 PLT TO MONITOR THE FLT INSTS. ALSO IT MIGHT HELP IF ALT ALERTERS SOUNDED AT +/-100 FT INSTEAD OF +/-300 FT.

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.