Narrative:

That morning I filed an IFR flight plan from ZZZ1 to ZZZ2 with planned departure of XA00. After running behind schedule (at home); in anticipation of the first flight plan dropping out of the system; I filed a second plan with a proposed departure of XC00. Both flight plans filed over duat. After receiving a clearance and waiting for release; I was told my flight plan dropped out of the system and I would have to re-file. Apparently; the second flight plan was nowhere to be found. I asked for and received an IFR clearance to climb to VFR. I knew tops were under 2500 ft MSL; and that at my anticipated cruise altitude of 8500 ft I could finish the flight VFR. The IMC climb was uneventful and tops were 2200 ft MSL. After canceling IFR; I transitioned the class B airspace over lax in the special flight rules corridor at 4500 ft MSL. After leaving the class B airspace (still under it though) and over smo; I started to notice decreased visibility; which in a few seconds rapidly deteriorated to IMC. Apparently the clouds I flew into were camouflaged by the lower cloud deck because I never saw them until I was in them. After quickly checking my instruments and autoplt settings to be sure I was stable in the transition to IMC I considered my options: 1) turn around. I decided against it. I didn't want to do anything unexpected in that often busy corridor; because I had no way of knowing if someone else was right behind me about to have the same problem. Also; dropping to the 3500 ft MSL altitude of the return direction was also in the category of 'unexpected move' that could cause problems with local IFR traffic. Because of my transponder code; ATC would be expecting me to proceed normally through the corridor. 2) proceed on as planned. I could start my climb after getting out from under the outer class B ring; and would quickly be above the clouds. I decided against it because of potential conflict with IFR traffic arriving/departing vny or any of the local airports. 3) call ATC and ask for a clearance. I called; explained my situation; and asked for a climb though the class B to VFR conditions. We had a little dialog about my situation; ratings; etc. I didn't get the climb immediately; but soon got an IFR clearance with headings; and an eventual climb to VFR conditions (tops at 5400 ft MSL). After canceling IFR in VFR conditions I was given a phone number to call. During the call I was reminded about the dangers associated with the situation I had caused and suggested I plan more carefully next time. Good advice. When checking the WX that morning I was working under an IFR assumption. Rising terrain over the santa monica mountains was the certain cause of what had happened; but I missed it in my planning. It was not relevant to my IFR flight. Before making the decision to proceed VFR; I should have carefully checked the WX again (I had it on my computer in the cockpit) to be sure there were no issues with my planned route of flight. In fact; I could have made my climb to the south and requested a class B clearance through the hollywood park route (7000-10000 ft); which would have put me well over the clouds. Even if that was refused I could have climbed over the class B airspace to the south and just flew over the top. My initial planning was more than adequate for the originally planned flight. I had been checking the WX repeatedly that morning and the night before; and so had a very good mental picture of what to expect in an IFR flight. My error was in not stopping to completely re-think the situation for a VFR flight. I had a good mental picture of departure; cruise; and arrival conditions; but the special flight rules corridor was not part of my planning. Had I done so; I had several available VFR options; as well as the option of re-filing my IFR flight plan.

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Original NASA ASRS Text

Title: A VFR M20J PLT ENCOUNTERED IMC NEAR SMO AFTER CANCELING IFR. ATC RECLRED HIM TO CLB TO VMC UNDER IFR.

Narrative: THAT MORNING I FILED AN IFR FLT PLAN FROM ZZZ1 TO ZZZ2 WITH PLANNED DEP OF XA00. AFTER RUNNING BEHIND SCHEDULE (AT HOME); IN ANTICIPATION OF THE FIRST FLT PLAN DROPPING OUT OF THE SYS; I FILED A SECOND PLAN WITH A PROPOSED DEP OF XC00. BOTH FLT PLANS FILED OVER DUAT. AFTER RECEIVING A CLRNC AND WAITING FOR RELEASE; I WAS TOLD MY FLT PLAN DROPPED OUT OF THE SYS AND I WOULD HAVE TO RE-FILE. APPARENTLY; THE SECOND FLT PLAN WAS NOWHERE TO BE FOUND. I ASKED FOR AND RECEIVED AN IFR CLRNC TO CLB TO VFR. I KNEW TOPS WERE UNDER 2500 FT MSL; AND THAT AT MY ANTICIPATED CRUISE ALT OF 8500 FT I COULD FINISH THE FLT VFR. THE IMC CLB WAS UNEVENTFUL AND TOPS WERE 2200 FT MSL. AFTER CANCELING IFR; I TRANSITIONED THE CLASS B AIRSPACE OVER LAX IN THE SPECIAL FLT RULES CORRIDOR AT 4500 FT MSL. AFTER LEAVING THE CLASS B AIRSPACE (STILL UNDER IT THOUGH) AND OVER SMO; I STARTED TO NOTICE DECREASED VISIBILITY; WHICH IN A FEW SECONDS RAPIDLY DETERIORATED TO IMC. APPARENTLY THE CLOUDS I FLEW INTO WERE CAMOUFLAGED BY THE LOWER CLOUD DECK BECAUSE I NEVER SAW THEM UNTIL I WAS IN THEM. AFTER QUICKLY CHKING MY INSTS AND AUTOPLT SETTINGS TO BE SURE I WAS STABLE IN THE TRANSITION TO IMC I CONSIDERED MY OPTIONS: 1) TURN AROUND. I DECIDED AGAINST IT. I DIDN'T WANT TO DO ANYTHING UNEXPECTED IN THAT OFTEN BUSY CORRIDOR; BECAUSE I HAD NO WAY OF KNOWING IF SOMEONE ELSE WAS RIGHT BEHIND ME ABOUT TO HAVE THE SAME PROB. ALSO; DROPPING TO THE 3500 FT MSL ALT OF THE RETURN DIRECTION WAS ALSO IN THE CATEGORY OF 'UNEXPECTED MOVE' THAT COULD CAUSE PROBS WITH LCL IFR TFC. BECAUSE OF MY XPONDER CODE; ATC WOULD BE EXPECTING ME TO PROCEED NORMALLY THROUGH THE CORRIDOR. 2) PROCEED ON AS PLANNED. I COULD START MY CLB AFTER GETTING OUT FROM UNDER THE OUTER CLASS B RING; AND WOULD QUICKLY BE ABOVE THE CLOUDS. I DECIDED AGAINST IT BECAUSE OF POTENTIAL CONFLICT WITH IFR TFC ARRIVING/DEPARTING VNY OR ANY OF THE LCL ARPTS. 3) CALL ATC AND ASK FOR A CLRNC. I CALLED; EXPLAINED MY SITUATION; AND ASKED FOR A CLB THOUGH THE CLASS B TO VFR CONDITIONS. WE HAD A LITTLE DIALOG ABOUT MY SITUATION; RATINGS; ETC. I DIDN'T GET THE CLB IMMEDIATELY; BUT SOON GOT AN IFR CLRNC WITH HDGS; AND AN EVENTUAL CLB TO VFR CONDITIONS (TOPS AT 5400 FT MSL). AFTER CANCELING IFR IN VFR CONDITIONS I WAS GIVEN A PHONE NUMBER TO CALL. DURING THE CALL I WAS REMINDED ABOUT THE DANGERS ASSOCIATED WITH THE SITUATION I HAD CAUSED AND SUGGESTED I PLAN MORE CAREFULLY NEXT TIME. GOOD ADVICE. WHEN CHKING THE WX THAT MORNING I WAS WORKING UNDER AN IFR ASSUMPTION. RISING TERRAIN OVER THE SANTA MONICA MOUNTAINS WAS THE CERTAIN CAUSE OF WHAT HAD HAPPENED; BUT I MISSED IT IN MY PLANNING. IT WAS NOT RELEVANT TO MY IFR FLT. BEFORE MAKING THE DECISION TO PROCEED VFR; I SHOULD HAVE CAREFULLY CHKED THE WX AGAIN (I HAD IT ON MY COMPUTER IN THE COCKPIT) TO BE SURE THERE WERE NO ISSUES WITH MY PLANNED RTE OF FLT. IN FACT; I COULD HAVE MADE MY CLB TO THE S AND REQUESTED A CLASS B CLRNC THROUGH THE HOLLYWOOD PARK RTE (7000-10000 FT); WHICH WOULD HAVE PUT ME WELL OVER THE CLOUDS. EVEN IF THAT WAS REFUSED I COULD HAVE CLBED OVER THE CLASS B AIRSPACE TO THE S AND JUST FLEW OVER THE TOP. MY INITIAL PLANNING WAS MORE THAN ADEQUATE FOR THE ORIGINALLY PLANNED FLT. I HAD BEEN CHKING THE WX REPEATEDLY THAT MORNING AND THE NIGHT BEFORE; AND SO HAD A VERY GOOD MENTAL PICTURE OF WHAT TO EXPECT IN AN IFR FLT. MY ERROR WAS IN NOT STOPPING TO COMPLETELY RE-THINK THE SITUATION FOR A VFR FLT. I HAD A GOOD MENTAL PICTURE OF DEP; CRUISE; AND ARR CONDITIONS; BUT THE SPECIAL FLT RULES CORRIDOR WAS NOT PART OF MY PLANNING. HAD I DONE SO; I HAD SEVERAL AVAILABLE VFR OPTIONS; AS WELL AS THE OPTION OF RE-FILING MY IFR FLT PLAN.

Data retrieved from NASA's ASRS site as of January 2009 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.