Narrative:

Flight progressed normally from preflight through approximately one hour into the flight at cruise altitude FL330; in navigation mode. As pilot flying; I witnessed the aircraft spontaneously revert to heading mode (heading flashing). Immediately following this event; the display units filled with amber alerts; nearly all numeric readouts were replaced with amber X's; and nearly all sdcp cue switches illuminated. Attempts to return to navigation mode using the navigation button were unsuccessful. The captain immediately ordered that I don my O2 mask. We declared an emergency and descended. During descent; the captain assumed control of the aircraft while I consulted the QRH for the cabin altitude emergency checklist. We notified the lead flight attendant; and informed the passengers of a pressurization problem and our imminent arrival into a nearby divert airport; which was approximately 80 NM to the northeast. We then obtained the destination weather; set up the approach; ran the in range checklist; and calculated our landing weight to be within limits (the quantity of fuel used was one of very few numbers remaining on our displays). We asked for a gradual descent from 10;000 ft; as we were; by then; unpressurized; having heard the aural 'cabin altitude' alert at approximately 11;500 ft. We landed on runway 36 and taxied to the gate.

Google
 

Original NASA ASRS Text

Title: A B717 Panel Data Concentrator Unit (PDCU) failed at FL330 causing NAV; autoflight and pressurization system failures so an emergency was declared; the QRH complied with and the flight diverted to a nearby airport.

Narrative: Flight progressed normally from preflight through approximately one hour into the flight at cruise altitude FL330; in NAV mode. As pilot flying; I witnessed the aircraft spontaneously revert to heading mode (HDG flashing). Immediately following this event; the display units filled with amber alerts; nearly all numeric readouts were replaced with amber X's; and nearly all SDCP cue switches illuminated. Attempts to return to NAV mode using the NAV button were unsuccessful. The Captain immediately ordered that I don my O2 mask. We declared an emergency and descended. During descent; the Captain assumed control of the aircraft while I consulted the QRH for the Cabin Altitude emergency checklist. We notified the lead Flight Attendant; and informed the passengers of a pressurization problem and our imminent arrival into a nearby divert airport; which was approximately 80 NM to the northeast. We then obtained the destination weather; set up the approach; ran the In Range checklist; and calculated our landing weight to be within limits (the quantity of fuel used was one of very few numbers remaining on our displays). We asked for a gradual descent from 10;000 FT; as we were; by then; unpressurized; having heard the aural 'cabin altitude' alert at approximately 11;500 FT. We landed on Runway 36 and taxied to the gate.

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.