Narrative:

After climbing out of FL330 to FL370 the altitude alert did not function properly, then followed with the left autoplt moving the yoke forward and aft 2-3 inches 4 times in less than 2 seconds, followed by the cabin altitude instruments spinning like a propeller in both automatic 1 and 2 modes, followed by the no land 3 status, followed by the autothrottles disconnect and EICAS message several times, followed by the right autoplt tripping off. This was all over a 15 min period. A patch with dispatch and maintenance was made and after 30 mins, a decision was made to which airport to divert to for maintenance. We descended to FL240 due to the cabin altitude problem, not knowing where it was due to spinning dials. We landed safely in sfo and placed all items in the log. Sfo was picked from dispatch and maintenance for maintenance reasons. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a B757-200 and was delayed for 2 hours awaiting an air data computer shipped into the departure station to correct a previous log write-up. The reporter said the mechanic replaced the air data computer and accomplished a bite test of the computer and signed off the report. The reporter stated the mechanic did not perform a static leak check which the reporter thought was necessary. The reporter stated the aircraft had the center autoplt deferred as inoperative but not placarded and the circuit breakers were not pulled and locked out. The reporter said on climbing from FL330 it was noted the altitude alert system was not working and on leveloff at FL370 things began to happen like the yoke moving fore and aft, cabin pressure and altimeter flags in view, cabin pressure indicators pegged and the cabin altitude differential pressure indicator spinning like a propeller and the autothrottle disconnected. The reporter said a descent was made to FL240 due to concern about the pressurization but at no time did the aircraft lose pressurization. After the aircraft was landed and maintenance made a quick check of the left air data computer, it indicated 12 faults but no other details were received from maintenance.

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Original NASA ASRS Text

Title: A B757-200 IN CRUISE AT FL370 DIVERTED DUE TO NUMEROUS AIR DATA COMPUTER SERVED SYS FAILURES.

Narrative: AFTER CLBING OUT OF FL330 TO FL370 THE ALT ALERT DID NOT FUNCTION PROPERLY, THEN FOLLOWED WITH THE L AUTOPLT MOVING THE YOKE FORWARD AND AFT 2-3 INCHES 4 TIMES IN LESS THAN 2 SECONDS, FOLLOWED BY THE CABIN ALT INSTS SPINNING LIKE A PROP IN BOTH AUTO 1 AND 2 MODES, FOLLOWED BY THE NO LAND 3 STATUS, FOLLOWED BY THE AUTOTHROTTLES DISCONNECT AND EICAS MESSAGE SEVERAL TIMES, FOLLOWED BY THE R AUTOPLT TRIPPING OFF. THIS WAS ALL OVER A 15 MIN PERIOD. A PATCH WITH DISPATCH AND MAINT WAS MADE AND AFTER 30 MINS, A DECISION WAS MADE TO WHICH ARPT TO DIVERT TO FOR MAINT. WE DSNDED TO FL240 DUE TO THE CABIN ALT PROB, NOT KNOWING WHERE IT WAS DUE TO SPINNING DIALS. WE LANDED SAFELY IN SFO AND PLACED ALL ITEMS IN THE LOG. SFO WAS PICKED FROM DISPATCH AND MAINT FOR MAINT REASONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A B757-200 AND WAS DELAYED FOR 2 HRS AWAITING AN AIR DATA COMPUTER SHIPPED INTO THE DEP STATION TO CORRECT A PREVIOUS LOG WRITE-UP. THE RPTR SAID THE MECH REPLACED THE AIR DATA COMPUTER AND ACCOMPLISHED A BITE TEST OF THE COMPUTER AND SIGNED OFF THE RPT. THE RPTR STATED THE MECH DID NOT PERFORM A STATIC LEAK CHK WHICH THE RPTR THOUGHT WAS NECESSARY. THE RPTR STATED THE ACFT HAD THE CTR AUTOPLT DEFERRED AS INOP BUT NOT PLACARDED AND THE CIRCUIT BREAKERS WERE NOT PULLED AND LOCKED OUT. THE RPTR SAID ON CLBING FROM FL330 IT WAS NOTED THE ALT ALERT SYS WAS NOT WORKING AND ON LEVELOFF AT FL370 THINGS BEGAN TO HAPPEN LIKE THE YOKE MOVING FORE AND AFT, CABIN PRESSURE AND ALTIMETER FLAGS IN VIEW, CABIN PRESSURE INDICATORS PEGGED AND THE CABIN ALT DIFFERENTIAL PRESSURE INDICATOR SPINNING LIKE A PROP AND THE AUTOTHROTTLE DISCONNECTED. THE RPTR SAID A DSCNT WAS MADE TO FL240 DUE TO CONCERN ABOUT THE PRESSURIZATION BUT AT NO TIME DID THE ACFT LOSE PRESSURIZATION. AFTER THE ACFT WAS LANDED AND MAINT MADE A QUICK CHK OF THE L AIR DATA COMPUTER, IT INDICATED 12 FAULTS BUT NO OTHER DETAILS WERE RECEIVED FROM MAINT.

Data retrieved from NASA's ASRS site as of July 2007 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.