LA-250 (Renegade/Seawolf)
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 70; Flight Crew Total 1060; Flight Crew Type 1000
Situational Awareness
ATC Issue All Types; Inflight Event / Encounter VFR In IMC; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance
Human Factors; Weather; Procedure
This was a strange situation.My plan was to fly my aircraft VFR north around class B airspace from ALN to SUS. On my last flight; on one radio; I had an intermittant issue and I wanted it looked at. The avionics shop was at SUS and the technician was going to let me put it in his hangar on Sunday (today) and he would look at it.Flight conditions were MVFR over to SUS - 1;300 feet AGL at ALN and 1;800 feet AGL at SUS. It is a short 30 mile flight no tall obstructions. I checked weather at ALN and at SUS.  I then called ALN ground to get a taxi clearance for a VFR flight westbound to SUS. He asked me if I wanted flight following. I hadn't intended on asking for flight following; but with the low ceilings; I said yes and he gave me a squawk. I had not wanted to file an IFR plan because of the radio and the short flight.On departure from ALN; I contacted STL approach to identfy myself for the flight following. The STL approcah controller immediately vectored [me] to Cardinal; which is over Lambert; and told me to climb to 3;500 feet - which was clearly in IMC. I then made the assumption that the ALN tower had filed an IFR flight plan on my behalf and decided to follow the plan an ATC instructions.  Various vectors and altitudes were then given by ATC; which I followed.  About 2/3 of the way to SUS; Lambert ATC asked me about flight conditions and I told him IMC.  He then advised that I was on a VFR flight plan and asked if I was IFR rated and the aircraft was equiped for instrument flight - to which I replied affirmative to both.  He then told me I was converted to an IFR flight plan; was asked to climb to 4;000 feet and then vectored to the ILS 8R at SUS where I landed without incident.I had been unaware the ALN tower had filed a flight plan on my behalf - I thought I was only getting flight following. When I was directed into IMC; I made the assumption that they did file for me and that it was an IFR flight plan. I learned in an instant that it was not an IFR flight plan when I connected the dots of ATC placing me at 3;500 feet and asking me flight conditions. It then became clear to me in an instant that I had been directed into clouds by ATC while on a VFR flight plan.
LA25 pilot reported flying into IMC under a VFR flight plan because of lack of communication with ATC and making incorrect assumptions.