Cessna 210 Centurion / Turbo Centurion 210C; 210D
Flight Crew Instrument
Flight Crew Last 90 Days 45; Flight Crew Total 1480; Flight Crew Type 204
Situational Awareness
Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Declared Emergency
Human Factors; Weather
I was on a short; IFR flight; normally about 25 - 30 minutes. I had flown up earlier in the day for a meeting and was flying back to my home base. The earlier flight was partially IMC; but no icing at 10;000 feet; in and out of the clouds. On the return flight; I filed for 9;000 feet. I had a PIREP of 'light rime' icing at 10;000 feet; but nothing lower than that. My destination airport was VFR with 1;500 feet broken; 7;000 overcast and 10 miles visibility; OAT of 5 degrees Celsius. Although there was no icing reported at 9;000 feet; I knew it was a possibility and my plan; if I encountered icing; was either to do a 180 back or climb (I had a PIREP of tops at 11;500 feet). I also knew that the entire flight; with a tailwind; would have me in the clouds for maybe 20 minutes. I did not initially pick up any ice at 9;000. About ten minutes into the flight (more than a third of the way to my destination) I began to get some light rime. I had already turned on the pitot heat and heated prop.  Then; about 25 miles out from the destination; the airframe began to pick up ice very quickly. I went from having a light film on the leading edges to maybe 3/4 of an inch in less than ten minutes. I found myself 'between' my planned outs of turning back and climbing--I could have climbed; but I was approaching the destination. I asked ATC for lower; because the OAT was about minus 1 Celsius and I knew that it was above freezing only a thousand feet below my current altitude. Unfortunately; the MVA was 8;500 feet and I needed 8;000. I also knew that 8;000 feet was a 'safe' altitude relative to terrain and obstacles. Even though ATC knew I was iced up and in need of a way out; they could not offer me lower than 8;500 feet. The airplane was still flying OK; albeit 'heavier' and a tiny bit nose high. Indicated Airspeed was still OK and I was watching it closely. Unfortunately; the airframe was still accreting ice and I decided I could no longer wait to descend. I informed approach that I needed an 'emergency descent due to icing.' They acknowledged and immediately allowed 'emergency vectoring altitude down to 7;300 ft.' At 8;300 feet MSL; the ice started melting off the windscreen and at 8;000 I was VMC; no longer taking on ice; and it was slowly melting off the leading edges.I cancelled IFR; gave a heartfelt thanks to ATC; and proceeded to my destination; where I made a visual approach and landing. I called the TRACON to let them know everything was fine and to thank them again. What did I learn?-Even on a very short flight with what seemed to be solid 'outs;' I should have exercised the alternatives sooner 'either' climbed or turned around sooner. I have never seen icing conditions change that fast and now I have.-Declaring an emergency was the right thing to do and it got me out of the clouds. In retrospect; declaring even a few minutes earlier would have made a positive difference in how much ice accreted. ATC was able to give me a descent more than two thousand feet below MVA.
C210 pilot experiences icing conditions at 9;000 feet with no ability to descend due to a MVA of 8;500 feet. With the icing becoming excessive; pilot stresses urgency to ATC and a descent to 8;000 feet results in VMC and temperatures above freezing.