The right air data computer on a B747 failed and the crew elected to return to the departure airport...

Attributes
ACN	1345355
Time
Date	201603
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Air Data Computer
Person 1
Function	Pilot Not Flying Captain
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 28000 Flight Crew Type 900
Person 2
Function	Pilot Not Flying Relief Pilot First Officer
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 20000 Flight Crew Type 9000
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

Approximately 1:30 hours into our flight the first officer lost all of his flight instruments. We discovered we lost the right air data computer. The first officer selected left on his air data switch located on the instrument source select panel to recover his airspeed; altimeter and vsi to his pfd (primary flight display).we called dispatch to get a 3 way call with maintenance. Maintenance told us it's captains emergency authority to pull and reset the air data circuit breaker. Since there was no guidance in the QRH to deal with a lost air data computer I pulled and reset the circuit breaker to no avail.I made the decision to return to ZZZ based on the fact I pulled the air data circuit breaker; and did not want fly and additional 12 hours on one air data computer.we coordinated our return with dispatch and ATC. We started dumping fuel 80 miles out at 31;000 feet. We then flew a normal arrival and approach.

Original NASA ASRS Text

Title: The Right Air Data Computer on a B747 failed and the Crew elected to return to the departure airport.

Narrative: Approximately 1:30 hours into our flight the first officer lost all of his flight instruments. We discovered we lost the right Air Data Computer. The first officer selected left on his Air Data switch located on the instrument source select panel to recover his airspeed; altimeter and VSI to his PFD (Primary Flight Display).We called dispatch to get a 3 way call with maintenance. Maintenance told us it's Captains emergency authority to pull and reset the Air Data circuit breaker. Since there was NO GUIDANCE in the QRH to deal with a lost Air Data Computer I pulled and reset the circuit breaker to no avail.I made the decision to return to ZZZ based on the fact I pulled the Air Data circuit breaker; and did not want fly and additional 12 hours on one Air Data computer.We coordinated our return with dispatch and ATC. We started dumping fuel 80 miles out at 31;000 feet. We then flew a normal arrival and approach.

Data retrieved from NASA's ASRS site 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.