G1 captain inadvertently disconnected autoplt and descended below assigned altitude with mem TRACON.

Attributes
ACN	602056
Time
Date	200312
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mem.tracon
State Reference	TN
Altitude	msl bound lower : 7000 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mem.tracon
Operator	other
Make Model Name	Gulfstream I (Large Turboprop)
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : multi engine pilot : cfi pilot : atp pilot : instrument
Experience	flight time last 90 days : 55 flight time total : 4750 flight time type : 1600
ASRS Report	602056
Person 2
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 100 flight time total : 14000 flight time type : 250
ASRS Report	602057
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was commanding a G3 with 8 passenger on a flight from tvr to mem. This was my second flight in this aircraft, the first was a .8 hour check out consisting of 4 takeoff and lndgs. The problem occurred as a result of the placement of the 'go around' button on the throttles. I have over 1000 hours in G2's and G3 and all have had gear horn silence buttons on the throttles. Therefore, as I retarded the power to start descending, I inadvertently depressed the 'go around' button which turned off the autoplt. I turned the autoplt on and descended through 8000 ft, which was assigned, to 7000 ft. ATC queried me and assigned 7000 ft. I was still descending when ATC called. Thanks ATC mem.

Original NASA ASRS Text

Title: G1 CAPT INADVERTENTLY DISCONNECTED AUTOPLT AND DSNDED BELOW ASSIGNED ALT WITH MEM TRACON.

Narrative: I WAS COMMANDING A G3 WITH 8 PAX ON A FLT FROM TVR TO MEM. THIS WAS MY SECOND FLT IN THIS ACFT, THE FIRST WAS A .8 HR CHK OUT CONSISTING OF 4 TKOF AND LNDGS. THE PROB OCCURRED AS A RESULT OF THE PLACEMENT OF THE 'GAR' BUTTON ON THE THROTTLES. I HAVE OVER 1000 HRS IN G2'S AND G3 AND ALL HAVE HAD GEAR HORN SILENCE BUTTONS ON THE THROTTLES. THEREFORE, AS I RETARDED THE PWR TO START DSNDING, I INADVERTENTLY DEPRESSED THE 'GAR' BUTTON WHICH TURNED OFF THE AUTOPLT. I TURNED THE AUTOPLT ON AND DSNDED THROUGH 8000 FT, WHICH WAS ASSIGNED, TO 7000 FT. ATC QUERIED ME AND ASSIGNED 7000 FT. I WAS STILL DSNDING WHEN ATC CALLED. THANKS ATC MEM.

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.