Caravan 208B
Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 240; Flight Crew Total 2500; Flight Crew Type 1200
Situational Awareness
Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Weather
While flying into STL; conditions rapidly deteriorated from what was forecast. About 40 miles from from the field; once handed off to STL Approach we were were informed that STL just put out a new METAR including freezing rain. We had already reported moderate ice to the previous controller and they were aware we were looking for alternative altitudes and solutions. The STL controller immediately gave us the updated METAR and several pireps for the area including moderate ice reports and one severe from the direction we just came from about 15 min behind us. I checked with the controller what the weather at our filed alternate was as well as several other airports in the vicinity. Unfortunately this freezing rain was a rather wide band covering a very large area. Due to these rapidly deteriorating conditions; I asked for a short approach and any assistance they could give us to get down quickly; and informed them we were receiving moderate to severe icing. I decided that the quickest way in was in fact our primary airport. Alton was closer distance wise but when I asked about it; the controller told me that due to the traffic already going in it would be quicker to go to STL; so this is what we did.The aircraft was light ;just the crew on board; no passengers and this helped keep our minimum icing speed and even allowed me to climb back up to a higher altitude in between layers just the freezing rain to help with the icing problem. The controller got us in as quick as they could. We were able to maintain positive control and airspeed without any upsets or control abnormalities all the way down the approach. Once we landed and inspected the exterior; we saw all the indications of severe ice; however only one inch or so had accumulated in the unprotected areas; and none above the wing. However the bottom of the wing had run back ice that had formed up to almost a foot back. Fortunately the top of the wing was clear and I believe the airspeed helped here.Several aircraft behind me our company and others were also scrambling to get out of the wide spread icing condition. This was the worst icing encounter I have ever experienced. Unfortunately there was no real way to avoid this encounter as it was unforecast and by the time it was reported to us; we were already in it; limiting our options.Honestly; I wish our aircraft were equipped with TKS anti-ice systems instead of boots. This would have seriously reduced the risk of the freezing rain encounter in my opinion; as more of the surface areas are protected. Too bad you can't make an Airworthiness Directive that requires operators to convert to that system.
C208 Captain reports encountering unforecast freezing rain approaching his destination; with similar conditions throughout a widespread area. The reporter elects to continue to destination with the help of ATC to achieve a rapid descent and approach.