Narrative:

We were rapidly approaching some buildups ahead. I was the PNF so I requested to ATC for permission to deviate. This took a while because the frequency was congested. The first officer (PF) deviated about 5 degrees to the left since this is within the normal accuracy ATC expects us to fly a heading. At that time I noticed the first officer had turned off the autoplt. He canceled the autoplt warning and did not tell me it was off. I was looking out the window at the WX and trying to talk to ATC. ATC called us and asked what our altitude was. I told ATC our altitude was 14400 ft and going back to 14000 ft. My first officer immediately corrected. I later discovered that our altitude warning system was not working properly. It should have warned us at 250 ft but it did not. I guess I should have done a better job of monitoring the aircraft altitude. Also, I would recommend that when you turn off the autoplt there should be no way to disable the autoplt warning such as in the EMB145. Also, just prior to this event, we had a partial avionics failure. It is hard to describe here but it was distracting. The problem was immediately found using the aircraft's QRH. Supplemental information from acn 512390: while cruising at FL290, we experienced a master caution and got an EICAS message stating that our data acquisition unit 2A was inoperative. The message cleared within 5 seconds. For the next 25 mins, the message popped on and off. The captain reviewed the QRH to see what procedure was possibly needed in case the message did not clear. Approximately 70 mi from cle we were cleared down to 14000 ft. The aircraft leveled off at 14000 ft (autoplt on). Within a few mins of leveling off at that altitude, the captain and I elected to deviate to the left for buildups. I elected to disengage the autoplt as it was getting very bumpy. At the same time, we got the same master caution. This time the message did not clear. The loss of the data acquisition unit caused us to lose all indications on the right side of the aircraft (including the #2 engine only amber dashes). The aircraft began drifting upward very slowly until reaching 14430 ft. At that point, I reversed immediately. These were the contributing factors to the incident: 1) failure of the altitude alerter! This warning is supposed to go off if your altitude is off by more than 250 ft. 2) failure by myself to 'fly the airplane.' as PF, I found myself involved with the caution, and putting less focus on the flying. It was VMC at the time (mixed) and spent time looking outside as well as listening to the captain as he read the QRH.

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Original NASA ASRS Text

Title: EMB145 FO ALLOWED ACFT TO CLB ABOVE ASSIGNED INTERMEDIATE ALT.

Narrative: WE WERE RAPIDLY APCHING SOME BUILDUPS AHEAD. I WAS THE PNF SO I REQUESTED TO ATC FOR PERMISSION TO DEVIATE. THIS TOOK A WHILE BECAUSE THE FREQ WAS CONGESTED. THE FO (PF) DEVIATED ABOUT 5 DEGS TO THE L SINCE THIS IS WITHIN THE NORMAL ACCURACY ATC EXPECTS US TO FLY A HDG. AT THAT TIME I NOTICED THE FO HAD TURNED OFF THE AUTOPLT. HE CANCELED THE AUTOPLT WARNING AND DID NOT TELL ME IT WAS OFF. I WAS LOOKING OUT THE WINDOW AT THE WX AND TRYING TO TALK TO ATC. ATC CALLED US AND ASKED WHAT OUR ALT WAS. I TOLD ATC OUR ALT WAS 14400 FT AND GOING BACK TO 14000 FT. MY FO IMMEDIATELY CORRECTED. I LATER DISCOVERED THAT OUR ALT WARNING SYS WAS NOT WORKING PROPERLY. IT SHOULD HAVE WARNED US AT 250 FT BUT IT DID NOT. I GUESS I SHOULD HAVE DONE A BETTER JOB OF MONITORING THE ACFT ALT. ALSO, I WOULD RECOMMEND THAT WHEN YOU TURN OFF THE AUTOPLT THERE SHOULD BE NO WAY TO DISABLE THE AUTOPLT WARNING SUCH AS IN THE EMB145. ALSO, JUST PRIOR TO THIS EVENT, WE HAD A PARTIAL AVIONICS FAILURE. IT IS HARD TO DESCRIBE HERE BUT IT WAS DISTRACTING. THE PROB WAS IMMEDIATELY FOUND USING THE ACFT'S QRH. SUPPLEMENTAL INFO FROM ACN 512390: WHILE CRUISING AT FL290, WE EXPERIENCED A MASTER CAUTION AND GOT AN EICAS MESSAGE STATING THAT OUR DATA ACQUISITION UNIT 2A WAS INOP. THE MESSAGE CLRED WITHIN 5 SECONDS. FOR THE NEXT 25 MINS, THE MESSAGE POPPED ON AND OFF. THE CAPT REVIEWED THE QRH TO SEE WHAT PROC WAS POSSIBLY NEEDED IN CASE THE MESSAGE DID NOT CLR. APPROX 70 MI FROM CLE WE WERE CLRED DOWN TO 14000 FT. THE ACFT LEVELED OFF AT 14000 FT (AUTOPLT ON). WITHIN A FEW MINS OF LEVELING OFF AT THAT ALT, THE CAPT AND I ELECTED TO DEVIATE TO THE L FOR BUILDUPS. I ELECTED TO DISENGAGE THE AUTOPLT AS IT WAS GETTING VERY BUMPY. AT THE SAME TIME, WE GOT THE SAME MASTER CAUTION. THIS TIME THE MESSAGE DID NOT CLR. THE LOSS OF THE DATA ACQUISITION UNIT CAUSED US TO LOSE ALL INDICATIONS ON THE R SIDE OF THE ACFT (INCLUDING THE #2 ENG ONLY AMBER DASHES). THE ACFT BEGAN DRIFTING UPWARD VERY SLOWLY UNTIL REACHING 14430 FT. AT THAT POINT, I REVERSED IMMEDIATELY. THESE WERE THE CONTRIBUTING FACTORS TO THE INCIDENT: 1) FAILURE OF THE ALT ALERTER! THIS WARNING IS SUPPOSED TO GO OFF IF YOUR ALT IS OFF BY MORE THAN 250 FT. 2) FAILURE BY MYSELF TO 'FLY THE AIRPLANE.' AS PF, I FOUND MYSELF INVOLVED WITH THE CAUTION, AND PUTTING LESS FOCUS ON THE FLYING. IT WAS VMC AT THE TIME (MIXED) AND SPENT TIME LOOKING OUTSIDE AS WELL AS LISTENING TO THE CAPT AS HE READ THE QRH.

Data retrieved from NASA's ASRS site as of July 2007 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.