Narrative:

We were cruising VFR inbound to torrance from the psp area at night with a reported 40 mi visibility. Approaching sli, I called coast approach and requested an ILS to torrance airport in order to avoid any conflicting traffic. Approach gave me a squawk XXXX. Nearing sli they acknowledged 'radar contact, 4 mi from sli remain VFR, proceed direct sli, then heading 220.' I acknowledged this transmission west/O an altitude restriction because none was received. The visibility was unusually good for the la area (40 mi). About this time I saw what appeared to be an aircraft approaching 12 O'clock at my same altitude. Inasmuch as I was instructed to remain VFR, it was my responsibility to take evasive action which I did by commencing a descent. After losing approximately 500' the controller called and said I was instructed to 'maintain 4500'.' I told him I did not hear that restriction (neither did I acknowledge an altitude restriction). I immediately climbed back to the assigned altitude and proceeded outbnd on the 220 degree heading. The controller called an 'altitude alert' about the same time I realized what appeared to be the approaching aircraft (was either a bright STAR or an airliner many miles away). In order to avoid confusion between pilot and controller, when switching form VFR rules to IFR rules, the initial set of instructions should be phrased so as to leave no doubt that the pilot is required to act under positive control. The phrase 'remain VFR' during this communication is easily misunderstood. The controller should insist on a complete readback from the pilot during this changeover from VFR to IFR.

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Original NASA ASRS Text

Title: PLT MISTAKES LIGHT AT NIGHT FOR AN ACFT IN CLOSE PROX AND DESCENDS.

Narrative: WE WERE CRUISING VFR INBND TO TORRANCE FROM THE PSP AREA AT NIGHT WITH A RPTED 40 MI VISIBILITY. APCHING SLI, I CALLED COAST APCH AND REQUESTED AN ILS TO TORRANCE ARPT IN ORDER TO AVOID ANY CONFLICTING TFC. APCH GAVE ME A SQUAWK XXXX. NEARING SLI THEY ACKNOWLEDGED 'RADAR CONTACT, 4 MI FROM SLI REMAIN VFR, PROCEED DIRECT SLI, THEN HDG 220.' I ACKNOWLEDGED THIS XMISSION W/O AN ALT RESTRICTION BECAUSE NONE WAS RECEIVED. THE VISIBILITY WAS UNUSUALLY GOOD FOR THE LA AREA (40 MI). ABOUT THIS TIME I SAW WHAT APPEARED TO BE AN ACFT APCHING 12 O'CLOCK AT MY SAME ALT. INASMUCH AS I WAS INSTRUCTED TO REMAIN VFR, IT WAS MY RESPONSIBILITY TO TAKE EVASIVE ACTION WHICH I DID BY COMMENCING A DSCNT. AFTER LOSING APPROX 500' THE CTLR CALLED AND SAID I WAS INSTRUCTED TO 'MAINTAIN 4500'.' I TOLD HIM I DID NOT HEAR THAT RESTRICTION (NEITHER DID I ACKNOWLEDGE AN ALT RESTRICTION). I IMMEDIATELY CLBED BACK TO THE ASSIGNED ALT AND PROCEEDED OUTBND ON THE 220 DEG HDG. THE CTLR CALLED AN 'ALT ALERT' ABOUT THE SAME TIME I REALIZED WHAT APPEARED TO BE THE APCHING ACFT (WAS EITHER A BRIGHT STAR OR AN AIRLINER MANY MILES AWAY). IN ORDER TO AVOID CONFUSION BTWN PLT AND CTLR, WHEN SWITCHING FORM VFR RULES TO IFR RULES, THE INITIAL SET OF INSTRUCTIONS SHOULD BE PHRASED SO AS TO LEAVE NO DOUBT THAT THE PLT IS REQUIRED TO ACT UNDER POSITIVE CTL. THE PHRASE 'REMAIN VFR' DURING THIS COM IS EASILY MISUNDERSTOOD. THE CTLR SHOULD INSIST ON A COMPLETE READBACK FROM THE PLT DURING THIS CHANGEOVER FROM VFR TO IFR.

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.