PA-31 Navajo/Chieftan/Mojave/T1040
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 28; Flight Crew Total 15900; Flight Crew Type 310
Situational Awareness; Time Pressure; Training / Qualification
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Human Factors; Weather; Procedure
I was flying from home base to [an airport]; 10 NM away; to deliver the plane for its Annual Inspection. I had planned to leave early but the weather was 500 FT ceiling; 2 miles visibility and the lowest approach minimum at [my] destination was 1 mile visibility and 800 FT ceiling with a very short (2;000 FT) runway and no approach lights. I waited over 2 hours for weather to improve; but it didn't. I decided to request a special VFR clearance after phoning the FBO at [my destination]. They told me the visibility there was at least 3-4 miles and the ceiling was definitely 500 FT or better. I assumed the ceiling would be at least 500 FT all the way on the 4-5 minute flight. When I got about 2 miles east; the ceiling suddenly dropped; and I had to decide whether to stay at 500 FT AGL and pop into the clouds or descend to remain clear. I decided to descend and went down to what I estimated to be about 350 FT AGL. Even though it was a sparsely populated area; I flew over two housing developments below 500 FT AGL. Three miles from [my destination] I saw the airport and runway; and the ceiling increased. I made an uneventful landing and it wasn't until after I got out of the plane that I realized that I had busted the regulation for minimum altitude over a structure or vehicle.The basic cause was that I had made a false assumption that the ceiling would be at least 500 FT all the way since the two airports were only 10-11 miles apart. This was definitely a case of poor judgment on my part. In the future; I will not assume that the ceiling will remain uniform; and give myself margin for error. I should have waited until the ceiling was at least 800 FT to 1;000 FT. My desire to get the Annual underway ASAP because one of my partners planned to use the plane in two weeks also played a role similar to the old 'get-home-itis.'
PA31 pilot on a VFR flight descended to 350 FT over a residential area to avoid a low ceiling.