Narrative:

We became aware of an airspeed issue with our assigned aircraft on the morning we were asked to reposition that aircraft following its diversion that morning. Shortly after arriving at the aircraft that night; and while the captain was still reviewing the logbook; the mechanic who had worked on the aircraft came up to meet us and answer any questions that we had about the discrepancy. Our main question about the work done was that there had been an overspeed and that there had only been a visual inspection done on the aircraft. The mechanic explained that this was per the maintenance manual; explained the thoroughness of the visual inspection; and explained that internal damage would be reflected on the exterior of the aircraft. Prior to departure; the captain and I discussed being vigilant for airspeed issues during the flight. We also discussed other sources of airspeed information; namely the GS on the GPS monitor page of the FMS; and on the nd. We also reviewed unreliable airspeed procedures; and talked about noting power-settings so that we would know what to put in to remain in steady flight if an indication problem occurred. It was my leg; so the autopilot was on number 2. All indications and automation worked during the climbout; cruise; and initial descent. We were leveling at FL280; when I noticed the autothrottles adding an unusual amount of power. At almost the same time; the captain noticed the airspeed on her pfd drop suddenly. This was followed by an ECAM for an air data computer/IAS discrepancy. The airspeed on my side of the aircraft continued to match the airspeed on the standby indicator; and there was no change in the GS on the nd or GPS monitor; so we were able to see that my indications were accurate. Since the number 2 autopilot was engaged; it did not chase the indicated airspeed on the captain's side. This had been a big issue on the previous flight. The autothrottles did keep increasing thrust; so when the airspeed on my side started rising; I disconnected the autothrottles; and set them manually. At this point the captain ran the ECAM; and selected the opposite side air data computer. This seemed to solve the issue; and after several minutes we decided to retry the autothrottles. At this point they responded normally; and we were able to use them for the remainder of the flight. The only unusual aspect of the malfunction was during the initial level off when the problem occurred; the autopilot became sloppy. We were at FL280; with 280 selected; but the altitude alert began chiming; and the autopilot started a very slow climb while in altitude hold mode. I selected a small vertical speed down; but the slow climb continued; approaching 150 feet high. As I was about to disconnect the autopilot; the aircraft began responding; and once again leveled at 280; and worked normally the remainder of the flight. I believe that this all occurred after the air data computer was switched; so I have no explanation for this behavior; and it seems similar to some of the automation issues that the previous crew experienced. We discussed asking for priority from ATC; but decided that at worst we now had an automation issue; and that the aircraft seemed to be performing correctly. We did let center know that we had experienced some automation problems that may affect crossing restrictions etc. Center passed that information along; but it ended up not being an issue. We were very lucky in that we had the knowledge that this problem may occur. We were also lucky that it happened on the opposite side from the autopilot. I can see that for the previous crew it would have been very confusing with the aircraft pitching over; and the ensuing difficulty in figuring out what information was reliable. This incident was very educational for me. I realized how important it is to see that there is nothing wrong with the aircraft; only the indications/automation; and look for a way to return to a steady state of flight.

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Original NASA ASRS Text

Title: After Maintenance clearance an A300; crew ferried the aircraft which had diverted for an overspeed. During cruise; with the autopilot on 2; an ADC/IAS ECAM was displayed as the Captain's instruments and autothrottle indicated a trend toward overspeed until ADC 2 was selected.

Narrative: We became aware of an airspeed issue with our assigned aircraft on the morning we were asked to reposition that aircraft following its diversion that morning. Shortly after arriving at the aircraft that night; and while the Captain was still reviewing the logbook; the Mechanic who had worked on the aircraft came up to meet us and answer any questions that we had about the discrepancy. Our main question about the work done was that there had been an overspeed and that there had only been a visual inspection done on the aircraft. The Mechanic explained that this was per the Maintenance Manual; explained the thoroughness of the visual inspection; and explained that internal damage would be reflected on the exterior of the aircraft. Prior to departure; the Captain and I discussed being vigilant for airspeed issues during the flight. We also discussed other sources of airspeed information; namely the GS on the GPS Monitor page of the FMS; and on the ND. We also reviewed unreliable airspeed procedures; and talked about noting power-settings so that we would know what to put in to remain in steady flight if an indication problem occurred. It was my leg; so the autopilot was on number 2. All indications and automation worked during the climbout; cruise; and initial descent. We were leveling at FL280; when I noticed the autothrottles adding an unusual amount of power. At almost the same time; the Captain noticed the airspeed on her PFD drop suddenly. This was followed by an ECAM for an ADC/IAS discrepancy. The airspeed on my side of the aircraft continued to match the airspeed on the Standby Indicator; and there was no change in the GS on the ND or GPS Monitor; so we were able to see that my indications were accurate. Since the number 2 autopilot was engaged; it did not chase the indicated airspeed on the Captain's side. This had been a big issue on the previous flight. The autothrottles did keep increasing thrust; so when the airspeed on my side started rising; I disconnected the autothrottles; and set them manually. At this point the Captain ran the ECAM; and selected the opposite side ADC. This seemed to solve the issue; and after several minutes we decided to retry the autothrottles. At this point they responded normally; and we were able to use them for the remainder of the flight. The only unusual aspect of the malfunction was during the initial level off when the problem occurred; the autopilot became sloppy. We were at FL280; with 280 selected; but the altitude alert began chiming; and the autopilot started a very slow climb while in altitude hold mode. I selected a small vertical speed down; but the slow climb continued; approaching 150 feet high. As I was about to disconnect the autopilot; the aircraft began responding; and once again leveled at 280; and worked normally the remainder of the flight. I believe that this all occurred after the ADC was switched; so I have no explanation for this behavior; and it seems similar to some of the automation issues that the previous crew experienced. We discussed asking for priority from ATC; but decided that at worst we now had an automation issue; and that the aircraft seemed to be performing correctly. We did let Center know that we had experienced some automation problems that may affect crossing restrictions etc. Center passed that information along; but it ended up not being an issue. We were very lucky in that we had the knowledge that this problem may occur. We were also lucky that it happened on the opposite side from the autopilot. I can see that for the previous crew it would have been very confusing with the aircraft pitching over; and the ensuing difficulty in figuring out what information was reliable. This incident was very educational for me. I realized how important it is to see that there is nothing wrong with the aircraft; only the indications/automation; and look for a way to return to a steady state of flight.

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.