A300 flight crew experiences Autoflight system malfunctions after being dispatched with the Profile Mode of the MCP deferred. An emergency is declared and all automation is switched off followed by a raw data ILS to landing.
Synopsis
A300 flight crew experiences Autoflight system malfunctions after being dispatched with the Profile Mode of the MCP deferred. An emergency is declared and all automation is switched off followed by a raw data ILS to landing.
Narrative
Flight dispatched with Profile Mode deferred for both FMC's. Initial part of flight uneventful. About 2/3 of the way through the flight I noticed green light on the MCP NAV PB switch to the HDG PB. This action was confirmed on the FMA; our Lateral mode was now HDG. I mentioned it to the Captain and reselected NAV. About 15 minutes later we both noticed it happen again. As the flight progressed this occurred more and more frequently. The Captain communicated our problem with ATC. Later in the flight while experiencing other problems in the descent it also switched from HDG SEL to NAV on its own. During the descent I noticed the red 'FD2' warning flash on my PFD. It only lasted about a 1/2 second. This happened several times and seemed to increase in frequency as the descent progressed. Sometimes the 'FD2' flash was accompanied by the loss of AP2 and sometimes it wasn't. Sometimes the FD didn't even disappear when the 'FD2' flash appeared. Captain suggested switching to AP1. We did but AP1 still kicked off with the next 'FD2' failure. We tried this one more time with the same result. In my mind I kept thinking I was experiencing an FD2 failure and thought that the info on the Captain's PFD should be good since that is using FD1. I suggested to the Captain that he should fly the aircraft if he was getting good info on his PFD. He said I was doing a good job and switching controls would not help since he was experiencing the same problems. I was also remembering from a training event long ago that if FD2 fails I could simply select the Captain's Sys 1 on the F/O Switching Panel in order to have FD1 displayed on my PFD. I did not take this action since it appeared FD1 was also bad and this was re-reinforced by AP1 kicking off. My thinking was that if AP1 was engaged it would be responding to FD1 data. Therefore if it was kicking off; FD1 must be failing as well. I recall that at about 6;000 ft in the descent as we were being vectored for downwind the autothrottles failed and the ATS lever on the overhead panel kicked off. Captain placed the ATS lever back to ON and re-selected A/THR on the MCP. Autothrottles kicked off again. We may have tried one more reset. This is about the time while using HDG SEL for vectors that we were turning to an assigned heading and the aircraft reversed its turn as HDG SEL switched back to NAV (a variation of the problem discussed in first paragraph). At this point I decided to stick with the basics; fly the airplane with what I knew worked; and stop troubleshooting. I disconnected the Autopilot for the final time; switched to the Flight Path Vector (FPV); and used manual throttles. The A300 Autoflight System (AFS) consists of two autopilots; two flight directors; and an autothrottle system. None of these components were working. The Captain told me he was going to declare an emergency and I agreed with him. Using the FPV and with good raw data displayed on the PFD; I was able to successfully follow ATC vectors and descent instructions to intercept the localizer and fly the ILS 35L approach. On final we completed our configuration for landing and slowed to final approach speed which we computed to be 138 kts. Captain dialed in 138 in the SPD/MACH window on the MCP. The blue line appeared accurately on the PFD. As with other problems we experienced on this flight the blue line began to randomly flash off. When it did it was replaced with a red 'SPD SEL' message at the top of the speed scale on the PFD. Again; the problem increased in frequency and duration as the approach progressed. I struggled with maintaining the localizer on final. Capt did a very good job of recognizing this and giving me small heading corrections to shoot for and hold ('on glideslope; come two degrees left' for example). I do not know what caused our system malfunctions. It appears something was wrong with both FCC 1 and FCC 2. Incorporating more raw data approaches in to annual training might help crews to be prepared for a similar situation.
Second reporter narrative
Aircraft monitoring and control became a priority over exploring the AOM for solutions to transient and unusual failures. I decided to assist the PF with monitoring the degraded state of the automated flight systems. As we were given our first vector; airspeed restriction and a descent; we found the HDG SEL function would revert to NAV on its own; creating a major distraction. Seeing a cascade of problems developing; I declared an emergency in the event additional problems occurred. A sense of 'what's next?' caused me to weigh the benefits of holding and contacting Dispatch and Maintenance Control for advice versus getting the airplane on the ground before other systems failed. At this point; I had lost confidence in the airplane. While on downwind; the auto throttle system failed. At this point; we had an Airbus with manual throttles; no flight directors; no autopilot and an MCP that was actually working against us. At no time did ECAM offer any assistance. As we flew into the under cast; managing the approach became a priority. My FO was flying very well; and I elected to monitor and assist him in flying the ILS. We landed and were escorted by CFR to the ramp. I then wrote up the airplane with the three additional failures that occurred late in the approach; totaling six. The sequential failure of multiple automated systems was unexpected. Although I flew 'raw data' approaches in initial training; I had no expectation an event like this could occur. I believe 14 years flying an old technology aircraft gave me the experience and confidence necessary to assess the loss of automation we faced as a threat and to assist my FO on a fairly challenging approach. 'No automation' could surprise a glass cockpit crew; especially when the failures are subtle and sequential. I'd suggest Airbus crews receive training to fly raw data approaches each recurrent training period. Having reviewed the systems manual since this flight; I am not sure what links these multiple failures. I look forward to hearing from Maintenance what corrective action was taken.
NASA callback
The reporter states that the aircraft was flown by another crew prior to this flight; but after the Profile Mode deferral; with no problems. He has not been informed by maintenance of what was required to return the aircraft to service. Reporter learned from the Chief Pilot that a Supplemental Control Unit (SCU); was replaced by Maintenance and the matter is considered closed.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.