Date: 201303
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Icing
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Climb
ATC / advisory: Center ZZZ
Aircraft component: Ice/Rain Protection System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; General Declared Emergency
Contributing factors: Aircraft; Weather
Primary problem: Aircraft

Narrative: During climb out enroute to destination; we turned the aircraft anti-ice systems on for climbing through the overcast. The SAT and TAT required anti-icing equipment on. I turned the wing and cowls off after we left icing conditions and the ice light was no longer illuminated. We did accumulate some ice during the climb near the top of the cloud deck. After selecting the left cowl off; we received a Left Cowl Caution message. We completed the checklist; which indicates a high-pressure condition exists in the system. After completion of the checklist we contacted the Dispatcher. Our destination was expecting snow; and if not snow it would at least be raining; and cold enough to require the anti-[ice] systems. We decided that our original destination was not an acceptable option. Our alternate was also not going to be acceptable. Due to the widespread under-cast we were limited in our diversion options. Our options as I saw them were to make a dash for the slightly warmer temps near the coast; and possibly box ourselves into an undesirable fuel state and still have to descend through icing conditions; or to find a suitable nearby airport. The Dispatcher and I decided that [an alternate airport] was probably the best option due to the close proximity and because we were familiar with the conditions at the field. Knowing that the icing was worst near the top of the cloud deck; the First Officer and I decided we would stay above the clouds until absolutely necessary; request the lowest altitude available; and descend as quickly as possible through the under-cast. I declared an emergency to facilitate our arrival and allow ATC to facilitate our descent requests. ATC gave us PIREPS from another aircraft that was also heading into [our new destination]; and accommodated our descent requests. We descended as quickly as possible to the assigned altitude of 2;100 FT; which was VMC. After landing I completed the maintenance write up and the First Officer walked around the aircraft. A few flights later we were talking about the high pressure condition; and I did not immediately consider the relief valve. She noted that the 14th stage relief valve was not activated. I thought the 14th stage pressure relief valve would pop and relieve a high pressure condition. Perhaps not or perhaps it was not safety wired correctly. The threats were the icing conditions without having anti-icing protection. The wide spread under-cast and cold temperatures were also a threat. I wanted to avoid having a low fuel condition and compounding our problem. Another threat was the potential for accumulating ice on the aircraft. I requested our landing data with ice accumulation; but the speeds were the same as without.I will double check the 14th stage relief valve for the high pressure condition. Of course it could have a sensor problem or not severe enough to activate the pressure valve.




Synopsis: CRJ-200 crew experienced an Ice Protection system warning; declared an emergency; and diverted to alternate.