Narrative:

We were in level flight at 13;000 ft; talking with center and cleared to descend 'via the jaike 2 arrival' into teb with the autopilot engaged. 7000 ft was programmed into the altitude preselect (regle at 7000) and VNAV was armed on the autopilot control panel by the captain (pilot flying). All appropriate altitudes were also loaded into the FMS and confirmed. Just prior to ilene intersection we both noticed a partial air data computer failure as the captain's #1 pfd altitude 'tape' disappeared and a red 'X' appeared. Both altitude preselect displays went blank as well; but the autopilot was still engaged and still apparently holding altitude according to the standby altimeter. There was no corresponding cas message on the EICAS however? I was the pilot monitoring and referred to the appropriate checklist; for which there is none for this particular failure? Neither of us have ever seen a partial failure like this one and the QRH had no procedure for this. We were both confused by the situation; so the captain decided to hand fly down to 7000 ft; as we couldn't really trust what were seeing. He also began a speed reduction to 250 KTS since we needed to be at 250 KTS and at 11000 ft over wacki intersection. The captain eventually selected his air data computer reversion switch in an attempt to regain the lost flight information. This worked and we regained our flight displays. In the confusion however; we both neglected to pay attention to our crossing restrictions over ilene (13;000ft) and then again at wacki (11;000 ft); undershooting both by approximately 1000 ft. Center brought it to our attention by saying 'for future reference' and restating the altitude restrictions on the arrival. We acknowledged; apologized and confessed that we were dealing with an air data computer failure and running checklists. The controller acknowledged our situation and handed us off to approach where we complied with our restriction of 7000 ft over regle intersection. There was never any traffic conflicts during this event and the flight continued on into teb without any further disruptions. Once on the ground; the captain contacted the assistant chief pilot and relayed the flight's events and completed the necessary maintenance write-ups. We were clearly task saturated during this event and the failure came at the worst possible time during the descent where we had multiple crossing restrictions. Compounding the problem was the fact that we had no corresponding checklist to fix the problem and in trying to figure out a solution we both became fixated on the failure and ended up missing crossing restrictions. I've been replaying the situation ever since and have concluded that in the future; one pilot has to be dedicated to precisely flying the airplane; ensuring we meet our crossing restrictions; speed compliance and navigation tracking. The other pilot should be working on the problem and a solution. We allowed the failure to temporarily distract us at the worst possible time. I will be much more vigilant in the future.

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Original NASA ASRS Text

Title: A CE-750's air data computer failed leading to a loss of altitude. The crew experienced task saturation; due in part to a lack of appropriate 'Abnormals' procedure for this problem; and subsequently missed arrival altitude crossing restrictions.

Narrative: We were in level flight at 13;000 FT; talking with Center and cleared to descend 'via the Jaike 2 arrival' into TEB with the autopilot engaged. 7000 FT was programmed into the altitude preselect (REGLE at 7000) and VNAV was armed on the autopilot control panel by the Captain (pilot flying). All appropriate altitudes were also loaded into the FMS and confirmed. Just prior to ILENE Intersection we both noticed a partial air data computer failure as the Captain's #1 PFD altitude 'tape' disappeared and a red 'X' appeared. Both altitude preselect displays went blank as well; but the autopilot was still engaged and still apparently holding altitude according to the standby altimeter. There was no corresponding CAS message on the EICAS however? I was the pilot monitoring and referred to the appropriate checklist; for which there is none for this particular failure? Neither of us have ever seen a partial failure like this one and the QRH had no procedure for this. We were both confused by the situation; so the Captain decided to hand fly down to 7000 FT; as we couldn't really trust what were seeing. He also began a speed reduction to 250 KTS since we needed to be at 250 KTS and at 11000 FT over WACKI intersection. The Captain eventually selected his ADC reversion switch in an attempt to regain the lost flight information. This worked and we regained our flight displays. In the confusion however; we both neglected to pay attention to our crossing restrictions over ILENE (13;000ft) and then again at WACKI (11;000 FT); undershooting both by approximately 1000 FT. Center brought it to our attention by saying 'for future reference' and restating the altitude restrictions on the arrival. We acknowledged; apologized and confessed that we were dealing with an air data computer failure and running checklists. The controller acknowledged our situation and handed us off to Approach where we complied with our restriction of 7000 FT over REGLE Intersection. There was never any traffic conflicts during this event and the flight continued on into TEB without any further disruptions. Once on the ground; the Captain contacted the Assistant Chief Pilot and relayed the flight's events and completed the necessary maintenance write-ups. We were clearly task saturated during this event and the failure came at the worst possible time during the descent where we had multiple crossing restrictions. Compounding the problem was the fact that we had no corresponding checklist to fix the problem and in trying to figure out a solution we both became fixated on the failure and ended up missing crossing restrictions. I've been replaying the situation ever since and have concluded that in the future; one pilot has to be dedicated to precisely flying the airplane; ensuring we meet our crossing restrictions; speed compliance and navigation tracking. The other pilot should be working on the problem and a solution. We allowed the failure to temporarily distract us at the worst possible time. I will be much more vigilant in the future.

Data retrieved from NASA's ASRS site as of April 2012 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.