As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATB- RETURNED TO AUS DUE TO ENGINE 1 VIBES ABOVE 4.0. CREW ALSO REPORTED FEELING A PULSE. MTC REPORTED HIGHEST N1 VIBE OBSERVED ON NUMBER ONE ENGINE WAS 4.2 UNITS. C/W FAN LUBE PER WORK CARD 7221-9601-01. C/W VIBE SURVEY PER AMM 71-00, N1 VIBES WITHIN LIMITS. (LP: 9439026, AIRCRAFT WAS GROUNDED)