Pilot of small transport twin jet excursioned from assigned altitude.

Attributes
ACN	148306
Time
Date	199006
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lex
State Reference	KY
Altitude	msl bound lower : 11800 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ind
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 50 flight time total : 12200 flight time type : 200
ASRS Report	148306
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera other other : unspecified cockpit
Resolutory Action	none taken : anomaly accepted
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I had been cleared to descend to 11000' 20 mi east of lex VOR. I was flying with autoplt coupled. I selected 11000', pushed the altitude select button and started my descent. Controller form ind ATC reported traffic at 11000' at my 1 O'clock position and asked if amend my altitude to 12000'. I entered 12000' into my computer and engaged the altitude select once again. Also changed my pitch control indicator. Unbeknown to me my pitch controller indicator shut off my altitude select. I was performing my descent, checklist at the time. I then visually saw the twin engine traffic that was previously called out. I verified I had him in sight. The aircraft autoplt allowed the aircraft to descend to approximately 11800', before I noticed the altitude select button was off. I manually disengaged the autoplt and returned aircraft to 12000'. I landed in lex, then later flew to atl where I was informed to contact ind approach.

Original NASA ASRS Text

Title: PLT OF SMT TWIN JET EXCURSIONED FROM ASSIGNED ALT.

Narrative: I HAD BEEN CLRED TO DSND TO 11000' 20 MI E OF LEX VOR. I WAS FLYING WITH AUTOPLT COUPLED. I SELECTED 11000', PUSHED THE ALT SELECT BUTTON AND STARTED MY DSNT. CTLR FORM IND ATC RPTED TFC AT 11000' AT MY 1 O'CLOCK POS AND ASKED IF AMEND MY ALT TO 12000'. I ENTERED 12000' INTO MY COMPUTER AND ENGAGED THE ALT SELECT ONCE AGAIN. ALSO CHANGED MY PITCH CONTROL INDICATOR. UNBEKNOWN TO ME MY PITCH CTLR INDICATOR SHUT OFF MY ALT SELECT. I WAS PERFORMING MY DSNT, CHKLIST AT THE TIME. I THEN VISUALLY SAW THE TWIN ENG TFC THAT WAS PREVIOUSLY CALLED OUT. I VERIFIED I HAD HIM IN SIGHT. THE ACFT AUTOPLT ALLOWED THE ACFT TO DSND TO APPROX 11800', BEFORE I NOTICED THE ALT SELECT BUTTON WAS OFF. I MANUALLY DISENGAGED THE AUTOPLT AND RETURNED ACFT TO 12000'. I LANDED IN LEX, THEN LATER FLEW TO ATL WHERE I WAS INFORMED TO CONTACT IND APCH.

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.