Narrative:

The WX for san jose was reported as 1300 ft and 7 mi visibility. I received a clearance out of the arsa instructing me to depart north, make a right turn, follow highway 101 south to south county airport. About 6 mi south of san jose, the WX deteriorated rapidly to less than 3 mi in haze and smog. I tried to call tower, then bay approach, but was unable to reach either facility. Later I learned that the yoke microphone button on the aircraft was defective and blocked out the hand microphone I was using. The flight visibility continued to decrease and rather than turn around into san jose traffic in reduced visibility and without radio communications or making turns in a valley with steep mountains on both sides, I elected to continue on my assigned heading and climbed through a 300 ft cloud layer. I set 7700 on the transponder and was through the cloud layer in about 30 seconds. After arriving VFR on top, I tuned in 7600 to signify that I had lost communication with ATC. I was able to reestablish communication with ATC through castle approach a few mins later. I invoked my emergency authority as PIC because I felt that it would be more dangerous to fly around in a valley in low visibilities or return to the san jose airport with no radio and WX conditions I had no way of confirming. If the communications problems continued I would have landed at an uncontrolled airport. I knew that I had terrain clearance if I maintained my assigned heading and I also knew that the cloud/smog bank was only a few hundred ft thick. I have read about numerous accidents where pilots have continued VFR in IFR conditions because they were either not instrument qualified, or were afraid of violations with the FAA. Our office has a policy that we do not fly single pilot IFR and this is why I did not file for an IFR climb to VFR on top.

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Original NASA ASRS Text

Title: SMA HAS MIKE PROBLEM ALONG WITH DETERIORATING WX. SQUAWKS 7700 AND CLBS THROUGH OVCST.

Narrative: THE WX FOR SAN JOSE WAS RPTED AS 1300 FT AND 7 MI VISIBILITY. I RECEIVED A CLRNC OUT OF THE ARSA INSTRUCTING ME TO DEPART N, MAKE A R TURN, FOLLOW HWY 101 S TO S COUNTY ARPT. ABOUT 6 MI S OF SAN JOSE, THE WX DETERIORATED RAPIDLY TO LESS THAN 3 MI IN HAZE AND SMOG. I TRIED TO CALL TWR, THEN BAY APCH, BUT WAS UNABLE TO REACH EITHER FACILITY. LATER I LEARNED THAT THE YOKE MICROPHONE BUTTON ON THE ACFT WAS DEFECTIVE AND BLOCKED OUT THE HAND MIKE I WAS USING. THE FLT VISIBILITY CONTINUED TO DECREASE AND RATHER THAN TURN AROUND INTO SAN JOSE TFC IN REDUCED VISIBILITY AND WITHOUT RADIO COMS OR MAKING TURNS IN A VALLEY WITH STEEP MOUNTAINS ON BOTH SIDES, I ELECTED TO CONTINUE ON MY ASSIGNED HDG AND CLBED THROUGH A 300 FT CLOUD LAYER. I SET 7700 ON THE TRANSPONDER AND WAS THROUGH THE CLOUD LAYER IN ABOUT 30 SECONDS. AFTER ARRIVING VFR ON TOP, I TUNED IN 7600 TO SIGNIFY THAT I HAD LOST COM WITH ATC. I WAS ABLE TO REESTABLISH COM WITH ATC THROUGH CASTLE APCH A FEW MINS LATER. I INVOKED MY EMER AUTHORITY AS PIC BECAUSE I FELT THAT IT WOULD BE MORE DANGEROUS TO FLY AROUND IN A VALLEY IN LOW VISIBILITIES OR RETURN TO THE SAN JOSE ARPT WITH NO RADIO AND WX CONDITIONS I HAD NO WAY OF CONFIRMING. IF THE COMS PROBLEMS CONTINUED I WOULD HAVE LANDED AT AN UNCTLED ARPT. I KNEW THAT I HAD TERRAIN CLRNC IF I MAINTAINED MY ASSIGNED HDG AND I ALSO KNEW THAT THE CLOUD/SMOG BANK WAS ONLY A FEW HUNDRED FT THICK. I HAVE READ ABOUT NUMEROUS ACCIDENTS WHERE PLTS HAVE CONTINUED VFR IN IFR CONDITIONS BECAUSE THEY WERE EITHER NOT INST QUALIFIED, OR WERE AFRAID OF VIOLATIONS WITH THE FAA. OUR OFFICE HAS A POLICY THAT WE DO NOT FLY SINGLE PLT IFR AND THIS IS WHY I DID NOT FILE FOR AN IFR CLB TO VFR ON TOP.

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.