Altitude deviation altitude excursion.

Attributes
ACN	292503
Time
Date	199412
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : vla
State Reference	IL
Altitude	msl bound lower : 28000 msl bound upper : 30000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Fokker 100
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 : first officer
Qualification	pilot : instrument pilot : atp
Experience	flight time last 90 days : 120 flight time total : 5000 flight time type : 900
ASRS Report	292503
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While at cruise altitude of FL280 with discretion to FL240, heading west direct vla, 40 east of vla, the autoplt started a gradual climb and slowly accelerated the climb until the aircraft approached FL300. The first officer first noticed the climb and immediately disconnected the autoplt and returned the aircraft manually to FL280. The altitude alerter did not go off because FL240 (the pilot's discretion altitude) was set in altitude window as is normal procedure. The pilots were briefing the approach during the incident. The climb began very insidiously by the autoplt for unknown reasons. The TCASII system was on at the time and did not advise of any conflicts. There were no traffic conflicts visible to either pilot. Center did not advise of any conflicts either. Possibly, if something were changed about the way the altitude alert works, the deviation could have been minimized. For example, if a lower altitude is set in the window, maybe the alerter should go off for deviations above the current altitude only. Also, during approach setup, pilots must be more vigilant than normal to avoid similar sits.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION.

Narrative: WHILE AT CRUISE ALT OF FL280 WITH DISCRETION TO FL240, HDG W DIRECT VLA, 40 E OF VLA, THE AUTOPLT STARTED A GRADUAL CLB AND SLOWLY ACCELERATED THE CLB UNTIL THE ACFT APCHED FL300. THE FO FIRST NOTICED THE CLB AND IMMEDIATELY DISCONNECTED THE AUTOPLT AND RETURNED THE ACFT MANUALLY TO FL280. THE ALT ALERTER DID NOT GO OFF BECAUSE FL240 (THE PLT'S DISCRETION ALT) WAS SET IN ALT WINDOW AS IS NORMAL PROC. THE PLTS WERE BRIEFING THE APCH DURING THE INCIDENT. THE CLB BEGAN VERY INSIDIOUSLY BY THE AUTOPLT FOR UNKNOWN REASONS. THE TCASII SYS WAS ON AT THE TIME AND DID NOT ADVISE OF ANY CONFLICTS. THERE WERE NO TFC CONFLICTS VISIBLE TO EITHER PLT. CTR DID NOT ADVISE OF ANY CONFLICTS EITHER. POSSIBLY, IF SOMETHING WERE CHANGED ABOUT THE WAY THE ALT ALERT WORKS, THE DEV COULD HAVE BEEN MINIMIZED. FOR EXAMPLE, IF A LOWER ALT IS SET IN THE WINDOW, MAYBE THE ALERTER SHOULD GO OFF FOR DEVS ABOVE THE CURRENT ALT ONLY. ALSO, DURING APCH SETUP, PLTS MUST BE MORE VIGILANT THAN NORMAL TO AVOID SIMILAR SITS.

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.