Narrative:

While in cruise flight at FL330 the autopilot disengaged; followed by auto throttle disengagement. We could not reset the autopilot or auto throttles on the first officer's side; so we switched the dfgc [digital flight guidance computer] to number 1 and attempted to engage both systems with the same result. At this time the captain advised ATC that we were unable to continue our cleared STAR because navigation and autopilot failure. ATC advised us to proceed direct to a VOR and we complied with conventional navigation. Shortly thereafter I noticed that the aircraft was experiencing a slight buffet with a cruise power setting of 83% N1. I was hand flying the aircraft and all flight control inputs were normal; in addition I noticed that all three airspeed indicators had different values; captain indicating approximately 200 KIAS; mine at the barber pole; and the standby at 250K. There were also moderate differences in altitude and pitch attitude displays. The aircraft showed level flight at FL330; however; as indicated by both ivsi indicators at 0 and all three altimeters steady. At this point I was not sure whether the buffet was coming from a potential over speed or the start of a stall. We both agreed to add power to see if the buffet would go away; thus giving us a positive indication as to whether we were slow or fast and to quickly determine which airspeed indicator was reliable. The captain also suggested I also lower the nose seeing that my pitch indicator showed 9 degrees pitch up. The aircraft buffet subsided with an increase in speed and settled in to a standby indicated airspeed of 260 KTS with a slight descent. There were no indications of a stall; master caution; or master warnings. We then noted several messages had now appeared that included air data computer 1 and 2 fail; dfgc 1 and 2 fail. At this point we declared an emergency and at the same time asked ATC about nearby airfields in VMC conditions. Looking westward out my window I could see the backside of the cold front and it appeared to be clear across the entire area so I suggested ZZZ might be a good landing option. We turned the aircraft to the west using the stand-by compass in conjunction with a vector from ATC towards ZZZ. We also requested a lower altitude so we could get into thicker air for better aircraft performance. ATC issued a clearance to descend to FL240. During the start of the descent I noticed that if the standby airspeed indicator reached 270 KTS the aircraft would start a slight buffet and we received the oral overspeed annunciation so I started off with a shallow decent. Upon reaching the edge of the cloud deck below we noticed what we thought to be ZZZ2 below us in the clear and double checked with center to verify that the airport in question was ZZZ2. We made a normal approach to a visual landing on runway 26 without further incident. ATC advised us of altitude; ground speed; and compass headings as a backup to the standby instruments.

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Original NASA ASRS Text

Title: An MD80 flight crew diverted to a nearby VMC airport when they suffered the loss of both ADCs and both DFGCs.

Narrative: While in cruise flight at FL330 the autopilot disengaged; followed by auto throttle disengagement. We could not reset the autopilot or auto throttles on the First Officer's side; so we switched the DFGC [Digital Flight Guidance Computer] to number 1 and attempted to engage both systems with the same result. At this time the Captain advised ATC that we were unable to continue our cleared STAR because navigation and autopilot failure. ATC advised us to proceed direct to a VOR and we complied with conventional navigation. Shortly thereafter I noticed that the aircraft was experiencing a slight buffet with a cruise power setting of 83% N1. I was hand flying the aircraft and all flight control inputs were normal; in addition I noticed that all three airspeed indicators had different values; Captain indicating approximately 200 KIAS; mine at the Barber Pole; and the standby at 250K. There were also moderate differences in altitude and pitch attitude displays. The aircraft showed level flight at FL330; however; as indicated by both IVSI indicators at 0 and all three altimeters steady. At this point I was not sure whether the buffet was coming from a potential over speed or the start of a stall. We both agreed to add power to see if the buffet would go away; thus giving us a positive indication as to whether we were slow or fast and to quickly determine which airspeed indicator was reliable. The Captain also suggested I also lower the nose seeing that my pitch indicator showed 9 degrees pitch up. The aircraft buffet subsided with an increase in speed and settled in to a standby indicated airspeed of 260 KTS with a slight descent. There were no indications of a stall; master caution; or master warnings. We then noted several messages had now appeared that included ADC 1 and 2 Fail; DFGC 1 and 2 Fail. At this point we declared an emergency and at the same time asked ATC about nearby airfields in VMC conditions. Looking westward out my window I could see the backside of the cold front and it appeared to be clear across the entire area so I suggested ZZZ might be a good landing option. We turned the aircraft to the west using the stand-by compass in conjunction with a vector from ATC towards ZZZ. We also requested a lower altitude so we could get into thicker air for better aircraft performance. ATC issued a clearance to descend to FL240. During the start of the descent I noticed that if the standby airspeed indicator reached 270 KTS the aircraft would start a slight buffet and we received the oral overspeed annunciation so I started off with a shallow decent. Upon reaching the edge of the cloud deck below we noticed what we thought to be ZZZ2 below us in the clear and double checked with Center to verify that the airport in question was ZZZ2. We made a normal approach to a visual landing on Runway 26 without further incident. ATC advised us of altitude; ground speed; and compass headings as a backup to the standby 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.