Air taxi pilot at cruise deviates from assigned altitude.

Attributes
ACN	142573
Time
Date	199004
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : llc
State Reference	NV
Altitude	msl bound lower : 14000 msl bound upper : 15500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	common carrier : air taxi
Make Model Name	Small Transport
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 40 flight time total : 3600
ASRS Report	142573
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

After approximately 3 1/2 hours of an eventual 5 1/2 hour flight from bil to oak, having just switched from heading to navigation mode on the autoplt, I was doing paperwork, (trend monitoring and VOR check) when slc called and said they showed my altitude readout as 15500' which when I looked down, was correct. When switching modes on the autoplt, my super giant sized finger evidently also hit the altitude hold and turned it off. I failed to properly monitor the gauges.

Original NASA ASRS Text

Title: AIR TAXI PLT AT CRUISE DEVIATES FROM ASSIGNED ALT.

Narrative: AFTER APPROX 3 1/2 HRS OF AN EVENTUAL 5 1/2 HR FLT FROM BIL TO OAK, HAVING JUST SWITCHED FROM HDG TO NAV MODE ON THE AUTOPLT, I WAS DOING PAPERWORK, (TREND MONITORING AND VOR CHK) WHEN SLC CALLED AND SAID THEY SHOWED MY ALT READOUT AS 15500' WHICH WHEN I LOOKED DOWN, WAS CORRECT. WHEN SWITCHING MODES ON THE AUTOPLT, MY SUPER GIANT SIZED FINGER EVIDENTLY ALSO HIT THE ALT HOLD AND TURNED IT OFF. I FAILED TO PROPERLY MONITOR THE GAUGES.

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.