EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
Flight Crew Overcame Equipment Problem
Aircraft; Weather
While working our way around thunderstorms that were near Chicago; we had pitot 2 freeze over in flight. We had no EICAS message indicating that we had a failure of the pitot heat. We had a CASS message indicating that there was a split in the airspeed. As we increased and decreased speed; the First Officer's indicated speed remained steady as the Captain and standby indicated speed matched. As we descended the First Officer showed a decrease in speed as we descended. We had a slight variation in altitude reading between the Captain and First Officer altimeter. As we descended below FL270 the ice apparently melted as the speed decreased to zero; followed by an increase to match the Captain and standby indicated speeds.The aircraft was never in a UAS as we controlled the plane by reference to the Captain and standby instruments.
While circumnavigating line of thunderstorms that passed through ORD area; we encountered high altitude icing accumulation (non ice detector detected) in IMC; causing pitot tube 2 to freeze and show incorrect information. At FL350; the PFD2 IAS comparison flag illuminated followed by gradual changes in PFD2 IAS conducive to altimeter type readings; (ie. no airspeed change with large power changes; and reduction of speed when descending). The indicator caused us to follow the QRH procedure which led us to inform ATC of the indication error and descend out of RVSM. Since the PFD 1 speed and ISIS (Integrated Standby Instrument System) indicated appropriately; the situation was nominal; as we were using data from pitot 1 and the CA/PF side. As in this incident the pitot 2 was the only frozen/failed tube; it resumed normal operation after descent into VMC and altitudes of approximately FL280-FL220 with additional increases of both SAT and TAT.
EMB-145LR flight crew reported pitot tube 2 iced up and showed incorrect information. Indications returned to normal when the flight descended into warmer temperatures.