Narrative:

Before we departed; we knew we would need a new route; which we received then; we called the fuel truck over to give us more fuel for the new route. Up to 8000lbs I believe. The new route had us going ZZZ (VOR).diesl.MSCT4 into iah. Once airborne; we needed to deviate around a low overhang from the line of thunderstorms to our east; which is why we needed a reroute. Made contact with center; and they immediately turned us north towards irw.tornn. DRLLR4 into iah. We told them that might not be possible. We tried to negotiate our way back down south; but to no avail. The captain and I determined we had enough fuel to reach irw plus extra to get us to an airport well east of the line of weather to refuel; and continue on to iah. We leveled off at FL370 for about 20-30 mins or so. Entered IMC conditions and noticed condensation on the inside of the windshield. Frost formed on the unheated portions of the windshield. About a minute later; we noticed that my airspeed began to drop rapidly; all the way down to zero in a matter of seconds. No changes to the aircraft have been made. The tl's were still set for lrc; and our altitude never changed. The captain got an amber IAS miscompare message on his pfd; and his airspeed indicator matched the standby airspeed indications. We recognized that pitot 2 has been blocked; most likely by ice. We ran the navigation/flight instrument failure (QRH) quick reference handbook procedure and it guided us to select the air data computer reversion button on my reversionary panel. By the time I pushed the button the captain noticed an amber altitude miscompare on his pfd as well; and we noticed my altimeter was about 200 ft high. The same QRH procedure applies to this new message. I pressed the air data computer reversion and I am now receiving cross side data for the captain's air data computer. The QRH also tells us we are unable rvsm. We notified ATC; and we requested to stay at FL370 for as long as possible for fuel. It took them about 10 mins to get back to us on that answer; but in the meantime; we stayed at FL370 and we realized if we can stay at FL370 we can make it all the way into iah without a fuel stop. We had a good tailwind that zipped us up to irw. ATC let us stay at FL370 until we made the turn toward the south. Once we made the turn southbound; ATC was giving us a series of radar vectors for sequencing into iah; we declared min fuel; and they instructed us to descend to FL280. We were still up by irw; so we knew descending to FL280 would significantly increase our fuel burn; so we decide to divert to ZZZ1. After lots of coordination between us and the dispatcher had called ahead to ZZZ1 and told them of our diversion; we amended the release and off we went. On our way to ZZZ1 in IMC we encountered some turbulence; and it kicked the autopilot off. Once we exited the turbulence the autopilot worked without issue. On the descent passing through 280-250 I decided to check and see if my pitot tube was still blocked. At this point we were in VMC conditions and still below freezing; but my airspeed and altitude were back to normal; and were matching up with the stand by and pitot 1 perfectly. So I at this point never re-selected the air data computer reversion button again. Once we landed in ZZZ1; we got more fuel and no passengers deplaned during the process. We were on the ground for less than 20 mins; before we departed to iah without any issues.once we landed in houston; we did not write up the pitot/static 2 blockage; because the issue resolved itself before landing. I do want to emphasize the air data computer failure was not the primary reason for diverting. Even if we had stayed up at FL370; the delayed vectors and sequencing by ATC used up too much fuel and we would have diverted anyway without the air data computer failing. Also we did not write it up because it wasn't a conventional failure of the air data computer because we did not get any red 'X's' over the airspeed and altitude tapes. Looking back on it now; we should have written up the pitot/static 2 blockage so maintenance can track the issue so they can determine if this is a significant problem on the emb-145 fleet; and or this particular aircraft. Overall I think us as a crew handled the situation very well. The captain and I had a shared mental model the whole flight. Our communication was spot on; and we effectively managed the threats as to not cause an uas. The flight attendant did an outstanding job keeping the passengers calm; and the coordination with our dispatcher was text book! The reason for my extended duty time was that I had about 6 hours of rest then had to teach a class at the training center. Which counts as fdp if I was going to fly later; which I didn't; because I would have had at least 10 hours after my training event. There were many threats associated with this flight. There was the line of severe weather along our route of flight; it was the last leg of a four day trip for the ca and flight attendant; and just the last leg of a day trip for me. The sun was setting. On the ground ATC reroute and an airborne ATC reroute. IMC conditions at high altitudes. Landing in ZZZ1; the tower was closed; and it had a shorter runway. We were able to use effective threat and error management to manage the threats associated with this flight; under abnormal circumstances so we never got into an uas. I would definitely have made sure that we wrote up the pitot/static blockage; so that it can be tracked in our maintenance program. On the ground [at our departure airport] I could have been more proactive and asked ATC if there were any problems with our filed route; so that we could have put more fuel on board; and avoided a diversion. I hope the company can use the data on the pitot/static 2 blockage to see if it is a recurring problem on our aircraft type; or this particular airplane.

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Original NASA ASRS Text

Title: EMB-145 crew diverted to alternate airport due to low fuel state caused by multiple vectors; icing and lower assigned altitude.

Narrative: Before we departed; we knew we would need a new route; which we received then; we called the fuel truck over to give us more fuel for the new route. Up to 8000lbs I believe. The new route had us going ZZZ (VOR).DIESL.MSCT4 into IAH. Once airborne; we needed to deviate around a low overhang from the line of thunderstorms to our east; which is why we needed a reroute. Made contact with center; and they immediately turned us north towards IRW.TORNN. DRLLR4 into IAH. We told them that might not be possible. We tried to negotiate our way back down South; but to no avail. The captain and I determined we had enough fuel to reach IRW plus extra to get us to an airport well east of the line of weather to refuel; and continue on to IAH. We leveled off at FL370 for about 20-30 mins or so. Entered IMC conditions and noticed condensation on the inside of the windshield. Frost formed on the unheated portions of the windshield. About a minute later; we noticed that my airspeed began to drop rapidly; all the way down to zero in a matter of seconds. No changes to the aircraft have been made. The TL's were still set for LRC; and our altitude never changed. The Captain got an amber IAS miscompare message on his PFD; and his airspeed indicator matched the standby airspeed indications. We recognized that pitot 2 has been blocked; most likely by ice. We ran the NAV/FLIGHT INSTRUMENT FAILURE (QRH) Quick Reference Handbook procedure and it guided us to select the ADC reversion button on my reversionary panel. By the time I pushed the button the captain noticed an amber ALT miscompare on his PFD as well; and we noticed my altimeter was about 200 ft high. The same QRH procedure applies to this new message. I pressed the ADC reversion and I am now receiving cross side data for the captain's ADC. The QRH also tells us we are unable RVSM. We notified ATC; and we requested to stay at FL370 for as long as possible for fuel. It took them about 10 mins to get back to us on that answer; but in the meantime; we stayed at FL370 and we realized if we can stay at FL370 we can make it all the way into IAH without a fuel stop. We had a good tailwind that zipped us up to IRW. ATC let us stay at FL370 until we made the turn toward the south. Once we made the turn southbound; ATC was giving us a series of radar vectors for sequencing into IAH; we declared min fuel; and they instructed us to descend to FL280. We were still up by IRW; so we knew descending to FL280 would significantly increase our fuel burn; so we decide to divert to ZZZ1. After lots of coordination between us and the dispatcher had called ahead to ZZZ1 and told them of our diversion; we amended the release and off we went. On our way to ZZZ1 in IMC we encountered some turbulence; and it kicked the autopilot off. Once we exited the turbulence the autopilot worked without issue. On the descent passing through 280-250 I decided to check and see if my pitot tube was still blocked. At this point we were in VMC conditions and still below freezing; but my airspeed and altitude were back to normal; and were matching up with the stand by and pitot 1 perfectly. So I at this point never re-selected the ADC reversion button again. Once we landed in ZZZ1; we got more fuel and no passengers deplaned during the process. We were on the ground for less than 20 mins; before we departed to IAH without any issues.Once we landed in Houston; we did not write up the Pitot/static 2 blockage; because the issue resolved itself before landing. I do want to emphasize the ADC failure was not the primary reason for diverting. Even if we had stayed up at FL370; the delayed vectors and sequencing by ATC used up too much fuel and we would have diverted anyway without the ADC failing. Also we did not write it up because it wasn't a conventional failure of the ADC because we did not get any red 'X's' over the airspeed and altitude tapes. Looking back on it now; we should have written up the pitot/static 2 blockage so maintenance can track the issue so they can determine if this is a significant problem on the EMB-145 fleet; and or this particular aircraft. Overall I think us as a crew handled the situation very well. The captain and I had a shared mental model the whole flight. Our communication was spot on; and we effectively managed the threats as to not cause an UAS. The Flight attendant did an outstanding job keeping the passengers calm; and the coordination with our dispatcher was text book! The reason for my extended duty time was that I had about 6 hours of rest then had to teach a class at the training center. Which counts as FDP if I was going to fly later; which I didn't; because I would have had at least 10 hours after my training event. There were many threats associated with this flight. There was the line of severe weather along our route of flight; it was the last leg of a four day trip for the CA and FA; and just the last leg of a day trip for me. The sun was setting. On the ground ATC reroute and an airborne ATC reroute. IMC conditions at high altitudes. Landing in ZZZ1; the tower was closed; and it had a shorter runway. We were able to use effective threat and error management to manage the threats associated with this flight; under abnormal circumstances so we never got into an UAS. I would definitely have made sure that we wrote up the pitot/static blockage; so that it can be tracked in our maintenance program. On the ground [at our departure airport] I could have been more proactive and asked ATC if there were any problems with our filed route; so that we could have put more fuel on board; and avoided a diversion. I hope the company can use the data on the pitot/static 2 blockage to see if it is a recurring problem on our aircraft type; or this particular airplane.

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.