A cargo pilot, flying a cessna 210, on the approach to tpa, descended without permission.

Attributes
ACN	451821
Time
Date	199910
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : tpa.airport
State Reference	FL
Altitude	msl bound lower : 1000 msl bound upper : 2100
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : tpa.tracon tower : tpa.tower
Operator	common carrier : air taxi
Make Model Name	Cessna 210 Centurion / Turbo Centurion 210C, 210D
Operating Under FAR Part	Part 135
Flight Phase	descent : approach descent : vacating altitude
Route In Use	arrival : vfr
Flight Plan	VFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : multi engine pilot : cfi pilot : commercial
Experience	flight time last 90 days : 101 flight time total : 1675 flight time type : 95
ASRS Report	451821
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : far non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : provided flight assist flight crew : returned to original clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was approaching tpa for landing and thought I had heard the controller clear me for the descent for landing at tpa. I was almost at traffic pattern altitude (estimated 1000-1500 ft MSL) when the controller told me I was supposed to be at 2100 ft, and to climb immediately to 2100 ft. So I complied, but I do not remember at any time being restr to 2100 ft. I guess I'll wait until I am certain the controller is telling me to descend. The radio stack is sometimes difficult to hear in this aircraft unless switches are set just right. Also the pressure of on-time performance may have contributed to any misunderstanding. The late hours may also have been a contributing factor. Perhaps written VFR arrival procedures would help.

Original NASA ASRS Text

Title: A CARGO PLT, FLYING A CESSNA 210, ON THE APCH TO TPA, DSNDED WITHOUT PERMISSION.

Narrative: I WAS APCHING TPA FOR LNDG AND THOUGHT I HAD HEARD THE CTLR CLR ME FOR THE DSCNT FOR LNDG AT TPA. I WAS ALMOST AT TFC PATTERN ALT (ESTIMATED 1000-1500 FT MSL) WHEN THE CTLR TOLD ME I WAS SUPPOSED TO BE AT 2100 FT, AND TO CLB IMMEDIATELY TO 2100 FT. SO I COMPLIED, BUT I DO NOT REMEMBER AT ANY TIME BEING RESTR TO 2100 FT. I GUESS I'LL WAIT UNTIL I AM CERTAIN THE CTLR IS TELLING ME TO DSND. THE RADIO STACK IS SOMETIMES DIFFICULT TO HEAR IN THIS ACFT UNLESS SWITCHES ARE SET JUST RIGHT. ALSO THE PRESSURE OF ON-TIME PERFORMANCE MAY HAVE CONTRIBUTED TO ANY MISUNDERSTANDING. THE LATE HRS MAY ALSO HAVE BEEN A CONTRIBUTING FACTOR. PERHAPS WRITTEN VFR ARR PROCS WOULD HELP.

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.