Small transport descends below assigned altitude causing less than standard separation.

Attributes
ACN	92268
Time
Date	198808
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : stl
State Reference	MO
Altitude	msl bound lower : 2500 msl bound upper : 3500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : stl tower : tpa
Operator	general aviation : corporate
Make Model Name	Small Transport
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 70 flight time total : 8700 flight time type : 4500
ASRS Report	92268
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 6000 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Inbound on the localizer in VFR conditions, assigned 3500' altitude until seeing traffic for the parallel runway. ATC asked several times if I had the traffic in sight. It was obvious that he wanted to clear me for a visual but could not until I saw the traffic. The last traffic report was one O'clock, 1 mi. I never saw him. At this point the controller turned me off a 1 1/2 to 2 mi final and advised I should be holding 3500'. Sure enough I had let my altitude slip to 2500. ATC brought me around to re-enter and I landed with no problem. I attribute this situation to 2 mind-sets. The controller thinking that I would see traffic at any moment and could be cleared for a visual. My mind was set on landing the aircraft after I sighted the runway, and I was preoccupied by reconfign the aircraft for landing and looking for traffic all at the same time.

Original NASA ASRS Text

Title: SMT DESCENDS BELOW ASSIGNED ALT CAUSING LESS THAN STANDARD SEPARATION.

Narrative: INBND ON THE LOC IN VFR CONDITIONS, ASSIGNED 3500' ALT UNTIL SEEING TFC FOR THE PARALLEL RWY. ATC ASKED SEVERAL TIMES IF I HAD THE TFC IN SIGHT. IT WAS OBVIOUS THAT HE WANTED TO CLR ME FOR A VISUAL BUT COULD NOT UNTIL I SAW THE TFC. THE LAST TFC RPT WAS ONE O'CLOCK, 1 MI. I NEVER SAW HIM. AT THIS POINT THE CTLR TURNED ME OFF A 1 1/2 TO 2 MI FINAL AND ADVISED I SHOULD BE HOLDING 3500'. SURE ENOUGH I HAD LET MY ALT SLIP TO 2500. ATC BROUGHT ME AROUND TO RE-ENTER AND I LANDED WITH NO PROB. I ATTRIBUTE THIS SITUATION TO 2 MIND-SETS. THE CTLR THINKING THAT I WOULD SEE TFC AT ANY MOMENT AND COULD BE CLRED FOR A VISUAL. MY MIND WAS SET ON LNDG THE ACFT AFTER I SIGHTED THE RWY, AND I WAS PREOCCUPIED BY RECONFIGN THE ACFT FOR LNDG AND LOOKING FOR TFC ALL AT THE SAME TIME.

Data retrieved from NASA's ASRS site as of August 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.