Crew leaves assigned altitude when they do not realize their autoplt altitude hold is disengaged.

Attributes
ACN	465980
Time
Date	200003
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : dekal
State Reference	FL
Altitude	msl bound lower : 16000 msl bound upper : 16500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zma.artcc
Operator	general aviation : corporate
Make Model Name	Citation II S2/Bravo
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : cfi pilot : atp pilot : instrument pilot : commercial pilot : multi engine
Experience	flight time last 90 days : 60 flight time total : 1900 flight time type : 100
ASRS Report	465980
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : instrument pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 75 flight time total : 3300 flight time type : 250
ASRS Report	465979
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllerb
Resolutory Action	controller : issued advisory flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cruise flight at 16000 ft. Crew given discretion to 8000 ft. Captain was working with GPS. Unknown to the crew, autoplt had disengaged from altitude hold and aircraft climbed to 16500 ft before center called to verify altitude. Crew responded 16500 ft descending to 8000 ft. Flight continued to destination uneventfully.

Original NASA ASRS Text

Title: CREW LEAVES ASSIGNED ALT WHEN THEY DO NOT REALIZE THEIR AUTOPLT ALT HOLD IS DISENGAGED.

Narrative: CRUISE FLT AT 16000 FT. CREW GIVEN DISCRETION TO 8000 FT. CAPT WAS WORKING WITH GPS. UNKNOWN TO THE CREW, AUTOPLT HAD DISENGAGED FROM ALT HOLD AND ACFT CLBED TO 16500 FT BEFORE CTR CALLED TO VERIFY ALT. CREW RESPONDED 16500 FT DSNDING TO 8000 FT. FLT CONTINUED TO DEST UNEVENTFULLY.

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.