Air taxi pilot descends below assigned. Believes cleared for approach.

Attributes
ACN	164584
Time
Date	199012
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lse
State Reference	WI
Altitude	msl bound lower : 3600 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air taxi
Make Model Name	Small Transport
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 3800 flight time type : 1200
ASRS Report	164564
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While acting as PIC on a flight from msp to lse, I was cleared pilot's discretion from my cruising altitude at 11000' to 5000'. Approximately 35 mi northwest of lse, I reported out of 11000' for 5000' and I reported lse in sight. Approximately 20 mi out of lse, ZMP gave me a 15 degree turn to the right for vectors for the visibility approach and for traffic. Approximately 10 mi west of lse, minneapolis informed me that I was only cleared to 5000', and that I had not been cleared for the approach. I had descended through 5000' and was at 3600' when ATC corrected me. I was instructed to return to 4000' and turned right to a heading of 180 degrees and I complied. Shortly afterward, I was cleared for the visibility approach to runway 36 at lse. The problem as I see it stems from the tendency of a pilot of relax from being on the sharp edge on a day when the ceilings and visibilities are unlimited. Also, I believe a contributing factor was the fact that I reported the airport in sight a considerable distance out, and by the time I had descended from 11000' to 5000', I had it in the back of my mind somewhere that I had been cleared for the approach--an unconscious assumption. The corrective action on my part is to try to train myself to always be sharp and keep, especially during those times when things are going smoothly.

Original NASA ASRS Text

Title: AIR TAXI PLT DESCENDS BELOW ASSIGNED. BELIEVES CLEARED FOR APCH.

Narrative: WHILE ACTING AS PIC ON A FLT FROM MSP TO LSE, I WAS CLRED PLT'S DISCRETION FROM MY CRUISING ALT AT 11000' TO 5000'. APPROX 35 MI NW OF LSE, I RPTED OUT OF 11000' FOR 5000' AND I RPTED LSE IN SIGHT. APPROX 20 MI OUT OF LSE, ZMP GAVE ME A 15 DEG TURN TO THE RIGHT FOR VECTORS FOR THE VIS APCH AND FOR TFC. APPROX 10 MI W OF LSE, MINNEAPOLIS INFORMED ME THAT I WAS ONLY CLRED TO 5000', AND THAT I HAD NOT BEEN CLRED FOR THE APCH. I HAD DSNDED THROUGH 5000' AND WAS AT 3600' WHEN ATC CORRECTED ME. I WAS INSTRUCTED TO RETURN TO 4000' AND TURNED RIGHT TO A HDG OF 180 DEGS AND I COMPLIED. SHORTLY AFTERWARD, I WAS CLRED FOR THE VIS APCH TO RWY 36 AT LSE. THE PROB AS I SEE IT STEMS FROM THE TENDENCY OF A PLT OF RELAX FROM BEING ON THE SHARP EDGE ON A DAY WHEN THE CEILINGS AND VISIBILITIES ARE UNLIMITED. ALSO, I BELIEVE A CONTRIBUTING FACTOR WAS THE FACT THAT I RPTED THE ARPT IN SIGHT A CONSIDERABLE DISTANCE OUT, AND BY THE TIME I HAD DSNDED FROM 11000' TO 5000', I HAD IT IN THE BACK OF MY MIND SOMEWHERE THAT I HAD BEEN CLRED FOR THE APCH--AN UNCONSCIOUS ASSUMPTION. THE CORRECTIVE ACTION ON MY PART IS TO TRY TO TRAIN MYSELF TO ALWAYS BE SHARP AND KEEP, ESPECIALLY DURING THOSE TIMES WHEN THINGS ARE GOING SMOOTHLY.

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.