A B777 FLT CREW IN ATLANTIC AIRSPACE FINDS THE SATCOM PRESET NUMBER FOR SHANWICK IS INCORRECT.

Narrative

AN ATTEMPT TO CONTACT SHANWICK ATC VIA SATCOM RESULTED IN AN UNASSIGNED 'NUM' STATUS MESSAGE. FURTHER INVESTIGATION WITH THE INVOLVEMENT OF DISPATCH DISCLOSED THAT THE PRESET NUMBER OF ABCDEF SHOULD BE ACBDEF. THIS ISSUE WAS SUBMITTED IN A WRITE-UP FOR THE ACFT. I AM CONCERNED THAT THIS IS A B777 FLEET ISSUE; NOT MERELY THIS ACFT. A CHK OF THE SATCOM ON A DIFFERENT ACFT HAS SHOWN SAME RESULT. WE HAVE BEEN ENCOURAGED DURING TRAINING TO RELY ON THE SATCOM AS A PRIMARY MEANS OF CONTACTING ATC WHEN IN OCEANIC CTL IN THE EVENT OF IRREGULAR OP OR EMER REQUIRING ATC COORD. IT IS NOT THE TIME TO TRY TO INTERP AN UNFAMILIAR STATUS MESSAGE RESULTING IN A FAILURE TO MAKE AN URGENT CONTACT IN THIS ENVIRONMENT. I AM REQUESTING A CHK OF THE ACCURACY OF ALL PRESET SATCOM NUMBERS IN THE B777 FLEET FOR ACCURACY. THIS ERROR APPEARS MERELY TO BE A TRANSPOSITION OF 2 DIGITS; BUT IT REMINDS US THAT UNLESS VERIFIED AND CHKED; THESE PRESET NUMBERS CAN RESULT IN CONFUSION AT BEST DURING A CRITICAL TIME OF NEED TO COMMUNICATE.