Narrative:

[It was a] dark night with minimal moon behind us and an undercast below. We had been through several areas of light to moderate turbulence and chop. Twice we had instructed the flight attendants that moderate turbulence procedures were in effect and to take their seats. But we were finally in smooth air. But then I noticed the isis (integrated standby instrument system) CRT screen was blanked out on the lower 60-65%. There was a light green square on the left and black to the right of the light green square. The airspeed and altitude windows were covered although the tops of each tape were visible. The line that defined the top of the blanked out area ran through the 5 degrees pitch up index. The top of the sky pointer was also in view. I studied it for about 30 seconds then pointed it out to my first officer. We discussed the situation. Neither of us had seen one of these new electronically displayed standby systems not work except when the airplane was totally powered down. We both decided that it would be impossible to fly using the small portion of the isis screen visible. We started a search for information in the QRH; the non-normal section of the pilot handbook; the flight operations manual (fom) and in the MEL. There were no references; except in the MEL. The MEL said we could not dispatch without an operable isis unless it was day VFR with no undercast along the route. We currently were over an undercast. I know the MEL is just used to dispatch a flight; but I feel it is always a good reference point. I decided we should get dispatch and maintenance in the loop. I was beginning to think that a diversion might be necessary. If we had any instrument or navigation failure; we had no back up with the current state of the isis.I sent the dispatcher two ACARS messages and waited. Since we didn't get a response; I decided to utilize the on-board phone we had on the flight deck. In short order; I was talking to our dispatcher. He brought in a maintenance controller to the conversation. About that time we received an ACARS reply from the same maintenance controller asking us to check our QRH and non-normals of the fom/pilot handbook. I let them know we had accomplished that and found nothing. I asked if there was any way to reset the system. The only thing he had was the circuit breaker on the overhead circuit breaker panel. I didn't like that idea and didn't think it would do anything for us. The system is designed to run on an internal battery for at least 30 minutes following a total electrical failure. I believe that it actually runs on the battery and the battery is continuously charged by the aircraft electrical system. I discussed the possibility of doing a diversion as we had now flown past the undercast and had good visual contact with the ground. My main concern was having an electrical failure over the mountainous region along our route. It was at that point that I decided to try pulling the circuit breaker for the system. I couldn't make it any worse as the system was unusable. And if the system was restored; there would be no concerns on my part. So I gave the aircraft to the first officer; got out of my seat and pulled the appropriate circuit breaker. The isis screen didn't even flicker; supporting my belief on how the system was set up. I did leave the circuit breaker out for 20 seconds at the maintenance controllers suggestion; but there were no changes when I reset it. We were past two possible diversion airports by now. The only real options ahead were two airports neither of which I have been into. Our destination was almost as close as any other diversion airport now; so I decided it best to continue to our destination. We landed in our destination without any further problems. The discrepancy was entered into the maintenance log after shutdown. I would like to have a little guidance for when items fail inflight. Some items can fail and there is no problem safely continuing to your destination. Losing your standby instruments would certainly be one area where many would like more guidance. Especially if the weather ahead was worse than what we had that night. Maybe something like the spar matrix; I look at losing the isis in the same way as losing all your crew oxygen. In that instance; even if you were at 10;000 ft; you still would have no way to combat smoke in the flight deck. Not having a working isis would not be good if we lost all flight deck instruments.

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Original NASA ASRS Text

Title: An A321 flight crew suffered the loss of their ISIS CRT (Integrated Standby Instrument System).

Narrative: [It was a] dark night with minimal moon behind us and an undercast below. We had been through several areas of light to moderate turbulence and chop. Twice we had instructed the flight attendants that moderate turbulence procedures were in effect and to take their seats. But we were finally in smooth air. But then I noticed the ISIS (Integrated Standby Instrument System) CRT screen was blanked out on the lower 60-65%. There was a light green square on the left and black to the right of the light green square. The airspeed and altitude windows were covered although the tops of each tape were visible. The line that defined the top of the blanked out area ran through the 5 degrees pitch up index. The top of the sky pointer was also in view. I studied it for about 30 seconds then pointed it out to my First Officer. We discussed the situation. Neither of us had seen one of these new electronically displayed standby systems not work except when the airplane was totally powered down. We both decided that it would be impossible to fly using the small portion of the ISIS screen visible. We started a search for information in the QRH; the non-normal section of the Pilot Handbook; the Flight Operations Manual (FOM) and in the MEL. There were no references; except in the MEL. The MEL said we could not dispatch without an operable ISIS unless it was day VFR with no undercast along the route. We currently were over an undercast. I know the MEL is just used to dispatch a flight; but I feel it is always a good reference point. I decided we should get Dispatch and Maintenance in the loop. I was beginning to think that a diversion might be necessary. If we had any instrument or navigation failure; we had no back up with the current state of the ISIS.I sent the Dispatcher two ACARS messages and waited. Since we didn't get a response; I decided to utilize the on-board phone we had on the flight deck. In short order; I was talking to our Dispatcher. He brought in a Maintenance Controller to the conversation. About that time we received an ACARS reply from the same Maintenance Controller asking us to check our QRH and Non-normals of the FOM/Pilot Handbook. I let them know we had accomplished that and found nothing. I asked if there was any way to reset the system. The only thing he had was the circuit breaker on the overhead circuit breaker panel. I didn't like that idea and didn't think it would do anything for us. The system is designed to run on an internal battery for at least 30 minutes following a total electrical failure. I believe that it actually runs on the battery and the battery is continuously charged by the aircraft electrical system. I discussed the possibility of doing a diversion as we had now flown past the undercast and had good visual contact with the ground. My main concern was having an electrical failure over the mountainous region along our route. It was at that point that I decided to try pulling the circuit breaker for the system. I couldn't make it any worse as the system was unusable. And if the system was restored; there would be no concerns on my part. So I gave the aircraft to the First Officer; got out of my seat and pulled the appropriate circuit breaker. The ISIS screen didn't even flicker; supporting my belief on how the system was set up. I did leave the circuit breaker out for 20 seconds at the Maintenance Controllers suggestion; but there were no changes when I reset it. We were past two possible diversion airports by now. The only real options ahead were two airports neither of which I have been into. Our destination was almost as close as any other diversion airport now; so I decided it best to continue to our destination. We landed in our destination without any further problems. The discrepancy was entered into the maintenance log after shutdown. I would like to have a little guidance for when items fail inflight. Some items can fail and there is no problem SAFELY continuing to your destination. Losing your standby instruments would certainly be one area where many would like more guidance. Especially if the weather ahead was worse than what we had that night. Maybe something like the SPAR matrix; I look at losing the ISIS in the same way as losing all your crew oxygen. In that instance; even if you were at 10;000 FT; you still would have no way to combat smoke in the flight deck. Not having a working ISIS would not be good if we lost all flight deck instruments.

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.