As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NO COMM DISPLAYED ON ACARS DISPLAY UNIT OVER OCEAN, ACARS SENDS OK IN VHF RANGE. CREW COMMENTS: SATCOM VOICE INOP. SATCOM DATALINK INTERMITTENT. LOW GAIN DISPLAYED ON FMC SATCOM MAIN MENU. REPLACED SDU PER MM. BITE FUNCTION CKS OKAY. ESTABLISHED COMM WITH SAMC.