Small transport near mzv altitude deviation while descending to another altitude.

Attributes
ACN	449720
Time
Date	199909
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mzv.airport
State Reference	IL
Altitude	msl bound lower : 17200 msl bound upper : 18000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Operating Under FAR Part	Part 135
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : cfi pilot : atp
Experience	flight time total : 2900
ASRS Report	449720
Person 2
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	altitude deviation : overshoot non adherence : clearance non adherence : far
Independent Detector	aircraft equipment : altitude alert other flight crewa
Resolutory Action	controller : issued alert flight crew : became reoriented 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:

We were asked to leave our filed altitude of FL190 and given a choice of which altitude we could change to 17000 ft, FL180, FL200, FL210. We chose FL180. Upon disengaging the autoplt and descending to FL180 we did not properly engage the altitude hold and the aircraft continued a slow descent to approximately 17200 ft before we recognized the change at about the same time the controller questioned us. This was a human performance problem and showed me that I always must remain as alert as possible -- even on severe clear, smooth days as I would in IMC, constantly checking and xchking my instruments.

Original NASA ASRS Text

Title: SMT NEAR MZV ALTDEV WHILE DSNDING TO ANOTHER ALT.

Narrative: WE WERE ASKED TO LEAVE OUR FILED ALT OF FL190 AND GIVEN A CHOICE OF WHICH ALT WE COULD CHANGE TO 17000 FT, FL180, FL200, FL210. WE CHOSE FL180. UPON DISENGAGING THE AUTOPLT AND DSNDING TO FL180 WE DID NOT PROPERLY ENGAGE THE ALT HOLD AND THE ACFT CONTINUED A SLOW DSCNT TO APPROX 17200 FT BEFORE WE RECOGNIZED THE CHANGE AT ABOUT THE SAME TIME THE CTLR QUESTIONED US. THIS WAS A HUMAN PERFORMANCE PROB AND SHOWED ME THAT I ALWAYS MUST REMAIN AS ALERT AS POSSIBLE -- EVEN ON SEVERE CLR, SMOOTH DAYS AS I WOULD IN IMC, CONSTANTLY CHKING AND XCHKING MY INSTS.

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.