C750 inbound to mry leaves assigned altitude prior to visual approach clearance issuance.

Attributes
ACN	594976
Time
Date	200309
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mry.airport
State Reference	CA
Altitude	msl bound lower : 4500 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : nct.tracon tower : mmun.tower
Operator	general aviation : corporate
Make Model Name	Citation X
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 4400 flight time type : 1400
ASRS Report	594976
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 151 flight time total : 19500 flight time type : 1100
ASRS Report	595274
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Level at 5000 ft MSL on a vector to mry airport. Controller told us to head to mry airport visually. The first officer mistook 'visually' for cleared for the visual approach. He started his descent. I was looking for the airport and did not notice he had started a descent until he was at 4500 ft MSL. At this point, I told him to initiate a climb. At that point, the controller told us we were off our altitude. I asked for the visual approach, because now I had the airport in sight. Visual approach clearance was granted, and we made an uneventful landing. Contributing factors: 1) first officer elected to fly aircraft raw data, which inhibited the altitude alerter. I would have been warned he was starting a descent. 2) first officer's not stating that he was beginning descent. 3) controller stating 'track visually to airport' can be a bit confusing. 4) I should not have allowed first officer to fly aircraft raw data. This inhibits altitude alert device.

Original NASA ASRS Text

Title: C750 INBOUND TO MRY LEAVES ASSIGNED ALT PRIOR TO VISUAL APCH CLRNC ISSUANCE.

Narrative: LEVEL AT 5000 FT MSL ON A VECTOR TO MRY ARPT. CTLR TOLD US TO HEAD TO MRY ARPT VISUALLY. THE FO MISTOOK 'VISUALLY' FOR CLRED FOR THE VISUAL APCH. HE STARTED HIS DSCNT. I WAS LOOKING FOR THE ARPT AND DID NOT NOTICE HE HAD STARTED A DSCNT UNTIL HE WAS AT 4500 FT MSL. AT THIS POINT, I TOLD HIM TO INITIATE A CLB. AT THAT POINT, THE CTLR TOLD US WE WERE OFF OUR ALT. I ASKED FOR THE VISUAL APCH, BECAUSE NOW I HAD THE ARPT IN SIGHT. VISUAL APCH CLRNC WAS GRANTED, AND WE MADE AN UNEVENTFUL LNDG. CONTRIBUTING FACTORS: 1) FO ELECTED TO FLY ACFT RAW DATA, WHICH INHIBITED THE ALT ALERTER. I WOULD HAVE BEEN WARNED HE WAS STARTING A DSCNT. 2) FO'S NOT STATING THAT HE WAS BEGINNING DSCNT. 3) CTLR STATING 'TRACK VISUALLY TO ARPT' CAN BE A BIT CONFUSING. 4) I SHOULD NOT HAVE ALLOWED FO TO FLY ACFT RAW DATA. THIS INHIBITS ALT ALERT DEVICE.

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.