Date: 201701
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: Marginal
Weather elements / visibility: Icing
Light: Night
Aircraft: EC135
Operator: Air Taxi
Operating under: Part 135
Mission: Ambulance
Flight phase: Cruise
Airspace: Class E ZZZ
Reporter organization: Air Taxi
Reporter function: Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Rotorcraft
Human factors: Situational Awareness; Training / Qualification
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed As Precaution
Contributing factors: Human Factors; Weather
Primary problem: Weather

Narrative: I was on a medical mission with patient on board. The forecast had shown low visibility along the route but nothing lower than four miles. There were several small snow flurries reported in the surrounding area but none along the route. I had checked the TAF [for the airports involved] as well as METARS along the route of flight. I had mentioned to my crew that we would have to stay extra vigilant with regards to low visibility on the flight. I was under NVGs on the flight and after taking off from the referring hospital I referenced the visibility to be greater than ten miles. About twenty five minutes into the flight I began to notice the visibility to be decreasing. I stated to my crew that we had low visibility ahead but was still approximately four miles (referenced by local airfield with lighted beacon and GPS distance). Shortly after the visibility in front was less; while out of my peripheral I could see much greater visibility. I scanned right; then left and estimated a four mile difference in visibility. I thought it may be the windscreen fogging up so I turned on the heating/demist. After a short time it had still not improved. It was at this time I thought something was wrong and flipped my goggles up and turned my lip light on. Instantly I noticed my windscreen was covered in ice! I immediately notified my crew and started a descent while making a radio call to the local airfield of my intent to emergency descend and land. Crew was able to see clearly out of side windows and was vigilantly looking for obstacles. We made a safe landing and notified dispatch via satellite phone. I set the aircraft to idle and placed the friction on the controls to exit. Once outside I noticed the ice on the windscreen was slushy as if starting to melt.  I cleared the windscreen and returned to the cockpit. I did not notice any other icing at this time. Once inside we initiated protocol to get the patient to proper care. Dispatch was still looking for a facility to take the patient when I happened to look out my right window and noticed a hospital less than a mile away. We found the hospital in our local landing zone guide and relayed the info to dispatch. Arrangements were made with that hospital and we were requested to re position to their helipad if possible. We had been sitting at idle for about twenty minutes and ceilings were higher than previously per weather station. The area was well lit from ground lights and I was able to clearly see the hospital and the cloud levels. Conditions had changed enough so a decision was made to relocate to the hospital. Once landed on the pad; I assisted the crew down into the hospital. I returned to the aircraft about an hour after landing and inspected the aircraft. It was at this time I noticed the icing on the blades. I contacted Operations to discuss the situation and possible relocation of the aircraft. The process of running the helicopter on the ground for a short time to try to loosen and shed the ice on the blades; then shutting down and inspecting the blades was discussed.  It was stated that if there was no ice found and icing conditions did not exist I could possibly relocate the aircraft to the airfield. I checked in with the crew to get an update on future logistics then returned to the aircraft about forty minutes later. At this time I went to proceed with the ground run and noticed the conditions had worsened. The helicopter had accumulated more ice on the structure and the blades and I witnessed rain freezing on contact to the windscreen. I referenced conditions at the airfield once again to find conditions subject to freezing fog and drizzle.I cannot say I have any suggestions on how to avoid flying into that situation. Of course hindsight is only great for learning from a situation but isn't present at the time of an event; but I would say I would not re position to the hospital without full shut down and complete post flight inspection if there was a chance todo it again. But at the time I used the information available to me and deemed the weather to have improved enough to proceed to the hospital.




Synopsis: Helicopter pilot reported encountering icing conditions and landed at the nearest airport.