A DC10-30 in cruise at FL310 diverted due to #1 air data computer failure.

Attributes
ACN	493831
Time
Date	200011
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bos.airport
State Reference	MA
Altitude	msl single value : 31000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	DC-10 30F
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp pilot : cfi pilot : multi engine
Experience	flight time type : 1500
ASRS Report	493831
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : diverted to another airport
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

In cruise at FL310, #1 CADC failed. Lost captain's (PF's) altimeter, airspeed, mach, ivsi, autoplt #1, autothrust. Xferred PF duties to first officer, performed company communication procedures. Consulted with dispatcher and maintenance control and elected to return to dtw rather than continue on to nat tracks. During CADC failure, captain's altitude fluctuated between FL290 and FL330 very rapidly. ZBW notified us they lost our mode C until we switched to #2 system. Returned to dtw. On descent, dumped 10000 pounds fuel and landed at 1000 pounds below maximum gross landing weight without incident.

Original NASA ASRS Text

Title: A DC10-30 IN CRUISE AT FL310 DIVERTED DUE TO #1 AIR DATA COMPUTER FAILURE.

Narrative: IN CRUISE AT FL310, #1 CADC FAILED. LOST CAPT'S (PF'S) ALTIMETER, AIRSPD, MACH, IVSI, AUTOPLT #1, AUTOTHRUST. XFERRED PF DUTIES TO FO, PERFORMED COMPANY COM PROCS. CONSULTED WITH DISPATCHER AND MAINT CTL AND ELECTED TO RETURN TO DTW RATHER THAN CONTINUE ON TO NAT TRACKS. DURING CADC FAILURE, CAPT'S ALT FLUCTUATED BTWN FL290 AND FL330 VERY RAPIDLY. ZBW NOTIFIED US THEY LOST OUR MODE C UNTIL WE SWITCHED TO #2 SYS. RETURNED TO DTW. ON DSCNT, DUMPED 10000 LBS FUEL AND LANDED AT 1000 LBS BELOW MAX GROSS LNDG WT WITHOUT INCIDENT.

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.