Narrative:

On climbout the flight encounters light to moderate mixed icing in the clouds 12;000-18;000 ft. I noticed my airspeed indicator tape on the eadi had a speed flag showing and the analog airspeed indicator was 0/45. I called out the anomaly. Crosschecked the captain's and standby airspeed indicators which both indicated normal. The captain handed me the QRH and said find a checklist for that. I completed the airspeed unreliable checklist. There was some confusion on the flight deck due to other indications present and not present on our alerting system. Examples: airspeed buffet announced in the FMC. No failure or non-heater lights within the pitot static annunciator system. All dashes in the thrust mode annunciator. Autothrottle limit annunciation. I personally just finished my yearly qualification with the company training the day before this trip. This situation was uncannily close to training scenarios the training department designed for this year. Located on my airline's training documents on the ipad/electronic flight bag. In short; I realized that we probably had the icing over of a pitot probe tube that affected the first officer's airspeed indicator and air data computer. The training I recently had helps me to understand that I could have a failed probe heater without the pitot heat lights illuminating. The flight continued on to the filed destination airport. Conditions were VFR. The first officers pitot heat was failing slowly not giving an indication of failure during the flight and only after testing it failed with the light on.slowly failing pitot probe heater without warning light annunciation.

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Original NASA ASRS Text

Title: During climb in icing conditions; a B737-400 First Officer had a SPD flag alert along with an airspeed loss; a FMC buffet alert and other indications that his pitot static system was icing even though no pilot system alerts were present.

Narrative: On climbout the flight encounters light to moderate mixed icing in the clouds 12;000-18;000 FT. I noticed my airspeed indicator tape on the EADI had a SPD flag showing and the analog airspeed indicator was 0/45. I called out the anomaly. Crosschecked the Captain's and standby airspeed indicators which both indicated normal. The Captain handed me the QRH and said find a checklist for that. I completed the airspeed unreliable checklist. There was some confusion on the flight deck due to other indications present and not present on our alerting system. Examples: airspeed buffet announced in the FMC. No failure or non-heater lights within the pitot static annunciator system. All dashes in the thrust mode annunciator. Autothrottle limit Annunciation. I personally just finished my yearly qualification with the company training the day before this trip. This situation was uncannily close to training scenarios the training department designed for this year. Located on my airline's training documents on the iPad/Electronic Flight Bag. In short; I realized that we probably had the icing over of a pitot probe tube that affected the First Officer's airspeed indicator and Air Data Computer. The training I recently had helps me to understand that I could have a failed probe heater without the Pitot Heat lights illuminating. The flight continued on to the filed destination airport. Conditions were VFR. The First Officers pitot heat was failing slowly not giving an indication of failure during the flight and only after testing it failed with the light on.Slowly failing pitot probe heater without warning light annunciation.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.