Narrative:

While descending...we were talking to approach. They descended us to 3;000 on a downwind leg 5 miles from ZZZ. They gave us a heading of 340 to pick up the visual. The frequency was very congested. After being on the 340 heading past the airport approximately 6 miles; ATC told us to turn heading 160 to the airport and this is where I thought I heard him say cleared for visual. I proceeded to configure the aircraft for landing and started my descent for the visual approach since we had the airport in sight. I proceeded to intercept the RNAV final and was following the vgp info; when ATC told us to check altitude and that we were assigned 3;000 feet. The non-flying pilot stated that we had the airport in sight and wanted to cancel IFR. ATC told us to squawk 1200 and switch to unicom.I believe the congested frequency had to do with the confusion of our clearance. I should have asked for vectors to the RNAV approach.

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Original NASA ASRS Text

Title: After ATC issued a turn toward the airport; a C750 flight crew descended from assigned altitude thinking they were cleared for a visual approach.

Narrative: While descending...we were talking to Approach. They descended us to 3;000 on a downwind leg 5 miles from ZZZ. They gave us a heading of 340 to pick up the visual. The frequency was very congested. After being on the 340 heading past the airport approximately 6 miles; ATC told us to turn heading 160 to the airport and this is where I thought I heard him say cleared for visual. I proceeded to configure the aircraft for landing and started my descent for the visual approach since we had the airport in sight. I proceeded to intercept the RNAV final and was following the VGP info; when ATC told us to check altitude and that we were assigned 3;000 feet. The non-flying pilot stated that we had the airport in sight and wanted to cancel IFR. ATC told us to squawk 1200 and switch to Unicom.I believe the congested frequency had to do with the confusion of our clearance. I should have asked for vectors to the RNAV approach.

Data retrieved from NASA's ASRS site 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.