Maintenance Powerplant; Maintenance Airframe
Situational Awareness; Troubleshooting; Communication Breakdown; Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Aircraft Damaged; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Procedure; Human Factors
Aircraft had MEL for Left Aft Galley Chiller Circuit Breaker (C/B) popped.  Aircraft came to ZZZ for Routine Overnight (RON) Maintenance between May 2013.  During troubleshooting for problem; it was discovered that the [electrical] harness for the Chiller had burned through and damaged the Floor Cross Beam at Station (Sta.) 1562; approximately Right Body Line (RBL) 28. A Maintenance Reporting Form was started with the original MEL in the Discrepancy Remarks section and the damage to the floor beam was added to the Reporting Form in the Open Items/Work to be accomplished section.  For two days; over multiple shifts; company Engineering was contacted and consulted with about the damage and acceptable limits.  Damage was blended and measured after blending. Reworked area also received a conductivity check by Inspection per Structural Repair Manual (SRM) 51-20-02 and Non-Destructive Testing  (NDT) Manual 51-00-03. Engineering was asked for an Engineering Authorization (EA) to cover the damage; but request was refused because Engineering believed damage to be within limits per the SRM after blending.  Reworked area was roto-peened and painted. I was not involved with repair to the damaged floor beam.  My only task was to re-pin the Left Chiller [electrical] connector after the wiring harness was repaired and reinstalled; and check the chiller after the damage to the floor beam was repaired.  My sign-offs on the Maintenance Reporting Form reflect this.  I was notified of the floor beam issue by the Midnight Hangar Supervisor after my return to work; after my scheduled days off.             After aircraft was released for service in the morning; Dayshift Engineering reviewed information sent to ZZZ Maintenance for floor beam damage and repair by Midnight Engineering and determined that damage was 'Out of Limits' and that blending and roto-peening was not an acceptable repair.  I cannot directly address why this event occurred.  Multiple departments were involved in this incident and I cannot comment on how Engineering determined what limits to use for the damage.  I do know that the aircraft was down for multiple shifts in ZZZ and there was constant communication between Maintenance and Engineering on the damage.  In the end; Maintenance followed the recommendations given to us by Engineering.  Aircraft had made one round trip revenue flight.  On its return to ZZZ; it was taken out of service and ferried to ZZZ1 for a Floor Beam Repair.  I have been told by ZZZ Supervision that Engineering has taken responsibility for this event and that they have submitted an Engineering Non-Compliance Reporting Form. I have no recommendations for avoiding a recurrence. Flight cancellation.
B767 aircraft was in ZZZ with a write-up for Left Aft Galley Chiller Circuit Breaker (C/B) popped. Engineering had determined that the damage was within limits. Then they reviewed their work in the morning and determined that their [allowed] limits on the Floor Beam [repair] were [actually] 'Out of Limits'. Engineering reviewed their paperwork on the next shift. I would have like to have had an Engineering Authorization (EA) stating that the damage was 'within limits'; instead of using the Structural Repair Manual (SRM).  Engineering had diagrams and calculations that should have been included with the paperwork. Hangar.
Two Mechanics report about a repair procedure to a B767 Cabin Floor Beam that was originally approved by company Midnight Engineering; but later considered to be 'Out of Limits' by their Dayshift Engineering. An electrical harness for the Aft Galley Chiller had burned through the harness and damaged the floor beam at Fuselage Station (Sta.) 1562.