A B757 Captain reported engine cowling delamination at high power settings in-flight. Maintenance was unable to see the flaws on the ground and the aircraft was mistakenly returned to service by local mechanics while Maintenance Control removed the aircraft from service for a cowling change.
Synopsis
A B757 Captain reported engine cowling delamination at high power settings in-flight. Maintenance was unable to see the flaws on the ground and the aircraft was mistakenly returned to service by local mechanics while Maintenance Control removed the aircraft from service for a cowling change.
Narrative
After an uneventful flight; went into terminal to pull up return flight plan. While at the computer a commuting 777 First Officer approached me and showed me pictures he'd taken of our right engine during the climb-out phase of our inbound flight. On the cowling; inboard; and just down from the engine strut and behind the de-icing ring were numerous area that appear to be oil canning. Each was almost circular and appeared to be 12 to 18 inches in circumference. They each appeared (in the photo) to be ¾ inch deep. The First Officer that took the pictures told me that when we went to climb power the dimples went away. I called the Technician and they informed me that some nose cowls were in need of repair and asked to have the pictures emailed to them by the commuting First Officer; which he did. In the meantime I asked Maintenance to inspect the engine and wrote the description of the oil canning/dimpling in the aircraft logbook. Maintenance inspected the exterior of the cowl; and by then I too had been emailed pictures of the cowl and showed Mechanics. After extensive external inspection Maintenance determined the aircraft was airworthy and signed the logbook accordingly. En route I got a message from Dispatch that asked me to call when on the ground. When I called the Dispatcher informed me that the aircraft had been taken out of service at the previous station. I informed him that this was the first time we had heard of it and that in fact our logbook had been signed and appeared legal and that is why we left. Obviously we would not have taken an aircraft that had an open item (that I had just written up) and was not airworthy and taken out of service. Within a few minutes of gate arrival at the next destination; several Mechanics arrived to inspect the aircraft and the logbook and also determined that based on what we knew at the previous station; the aircraft appeared airworthy and legal for flight. They also had seen and looked at my pictures of the cowl and suspected some sort of duct leak; based on the pictures only. When the aircraft was at cruise power and when shut down on the ground; there was no evidence of any oil canning; everything seemed intact and when tap tested also appeared solid. The aircraft was taken out of service.
Second reporter narrative
Aircraft was called out of service with a return to service time of parts plus 6 hours. The reason the aircraft was out of service was account of a delaminated engine cowling. As I was checking on options the station; I received an out time. I called Dispatch to remove the out time; assuming the station was moving the aircraft. I then received an off time shortly after that. I called the Technician; they still had the aircraft shown out of service. The aircraft was then shown in service in the computer and was taken back out of service upon landing. It seems the Mechanic signed the logbook bringing the aircraft back into service while that Station's Maintenance and Technician and Dispatch were under the assumption it was taken out of service.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.