C310 pilot departed assigned altitude.

Attributes
ACN	434885
Time
Date	199904
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : dpk.vor
State Reference	NY
Altitude	msl single value : 6000
Environment
Flight Conditions	IMC
Weather Elements	Rain Ice
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90.tracon
Operator	general aviation : personal
Make Model Name	Cessna 310/T310C
Operating Under FAR Part	Part 91
Flight Plan	IFR
Aircraft 2
Navigation In Use	other vortac
Flight Phase	cruise : level
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : atp pilot : commercial pilot : flight engineer pilot : multi engine
Experience	flight time last 90 days : 250 flight time total : 13000 flight time type : 200
ASRS Report	434885
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance
Independent Detector	atc equipment other atc equipment : radar other controllera
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft ATC Human Performance Weather
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Had filed to cruise at 6000 ft due to reported icing conditions at higher altitudes. Near dpk mostly clear ice started to build on my aircraft. Requested a descent to 4000 ft to get into warmer air. ATC didn't accommodate me at that time. As ice continued to build, a second request was made a couple of mins later. I thought I heard a clearance for me to descend to 4000 ft. Nearing 5000 ft, ATC questioned my descent and asked me to level at 5000 ft and turn left to 180 degrees due to another aircraft in the vicinity (though no conflict developed). It was not until I had a telephone conversation with the ATC supervisor, after landing, that it became clear that an altitude deviation had occurred. Becoming concerned about ice building on my aircraft, this appears to be a case of 'wishful hearing' on my part by looking for a quick clearance to descend into warmer air.

Original NASA ASRS Text

Title: C310 PLT DEPARTED ASSIGNED ALT.

Narrative: HAD FILED TO CRUISE AT 6000 FT DUE TO RPTED ICING CONDITIONS AT HIGHER ALTS. NEAR DPK MOSTLY CLR ICE STARTED TO BUILD ON MY ACFT. REQUESTED A DSCNT TO 4000 FT TO GET INTO WARMER AIR. ATC DIDN'T ACCOMMODATE ME AT THAT TIME. AS ICE CONTINUED TO BUILD, A SECOND REQUEST WAS MADE A COUPLE OF MINS LATER. I THOUGHT I HEARD A CLRNC FOR ME TO DSND TO 4000 FT. NEARING 5000 FT, ATC QUESTIONED MY DSCNT AND ASKED ME TO LEVEL AT 5000 FT AND TURN L TO 180 DEGS DUE TO ANOTHER ACFT IN THE VICINITY (THOUGH NO CONFLICT DEVELOPED). IT WAS NOT UNTIL I HAD A TELEPHONE CONVERSATION WITH THE ATC SUPVR, AFTER LNDG, THAT IT BECAME CLR THAT AN ALTDEV HAD OCCURRED. BECOMING CONCERNED ABOUT ICE BUILDING ON MY ACFT, THIS APPEARS TO BE A CASE OF 'WISHFUL HEARING' ON MY PART BY LOOKING FOR A QUICK CLRNC TO DSND INTO WARMER AIR.

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.