An A320 departed with a Cargo Smoke Detector System MEL deferral but was recalled to base while at cruise because the system may not have been properly deferred and in fact rendered completely inoperable.
Synopsis
An A320 departed with a Cargo Smoke Detector System MEL deferral but was recalled to base while at cruise because the system may not have been properly deferred and in fact rendered completely inoperable.
Narrative
While preparing the aircraft for departure; my First Officer found that a wind scan light was inoperative and also the ACARS was not functioning properly. Some ACARS messages were being sent and received but the system was slow and often displayed 'NO COMM'. Maintenance was notified via the radio of the two write ups. As I went through my preflight checks; although not required since it was not the first flight of the day; I performed the fire tests on the engines; APU system; and Cargo Smoke Detector system. I routinely perform this test on every new aircraft I get into as I have observed an occasional unsatisfactory test on the Cargo Smoke Detection system. On this particular day; the Cargo Smoke Detection system did not test properly as outlined in the flight manual when after pressing the Cargo smoke test button for 3 seconds; the associated lights and warning bells only cycled though once versus the proper two test cycles. I called maintenance on the radio approximately 30 minutes prior to departure and notified of the test failure. When the mechanic arrived; I again ran through the test sequence with him and we together verified that it was only testing once versus the required two test cycles. I told him that it appeared that one of the channels on the detector systems was inoperative. He said that he would look into it and would return with the required paperwork since ACARS was now inoperative. We started to receive some ACARS messages and one of them was from dispatch advising us to amend our release to show that the ACARS and the CHNL 2 smoke detector was inoperative. I was expecting maintenance to defer the Channel 2 and that we would be OK to continue as is. Shortly before our scheduled departure time; he returned with the maintenance release and said that he had difficulty getting all the paperwork done because the computers in the maintenance kiosks were also inoperative. I asked him if he needed to do a test of the system through the MCDU unit and he said that it was not necessary since the system had been deferred. He asked us to place the required deferral stickers in place and then left. As I looked at the maintenance release I saw that the write up said Gripe: 'Smoke Det Channel 2 will not test' Action: 'Complied with MEL.' We then pushed back; taxied out and departed normally. Approximately 30 minutes after departure we received a message from Dispatch advising us that we should return to [departure airport] since there was a concern that the Cargo Smoke detector system had been improperly deferred and that we may not have smoke detection capability. I contacted Dispatch via ARINC to verify that he wanted us to return and to make certain that the proper system had been deferred. He advised us to return to [departure airport] to make certain everything was in proper working order. We then advised ATC that we would need to return to [departure airport] due to a potential system malfunction and that we would like to have emergency equipment standing by since we would be landing overweight and I was concerned about potential brakes overheating. We returned to [departure airport] and landed at a weight of 147;500 with a normal descent rate and at a speed of approximately 140 KTS. Minimal braking was used. The emergency equipment met our flight as we taxied off the runway and after they verified that all was normal; we taxied to the gate.
Second reporter narrative
While preparing for departure; the first item that happened was the ACARs showed NO COMM shortly after initialization. While waiting for it to come back I decided to go outside and do my exterior inspection. While outside I noticed the Left Wing Scan light was inoperative. When I got back to the cockpit; I noticed the ACARs was still inoperative; so I notified MX that I had two Write-ups but could not send an MRM. I gave them both write ups verbally; and proceeded to continue my pre-flight duties. When the Captain came in he discovered that the Cargo Fire Suppression System was not testing properly. It was only cycling through one channel. The ACARs had been intermittent throughout our preflight; so we verbally notified MX about the Cargo Fire Suppression System also. After a few more minutes the mechanic came on to the flight deck. He told us the Wing Scan Light and the ACARs were deferred. After pushback the ACARs started working; so I checked the release verification. It showed Release 2 as valid and the MRD as being current; I did not actually read the new MRD. Push back; taxi; take off and climb were normal. At cruise altitude we got a message from Dispatch that we had left with an improper deferral. The entire Cargo Fire Protection System was deferred. There should have been no cargo loaded in either pit; the lavatories should have been closed off and unusable. The combination of factors definitely contributed to the mistake. The intermittent ACARs made communication with Dispatch; and Maintenance more difficult. The mechanic also told us he was having problems with his computer. I think he was having to find a computer he could use; and still trying to get things finished in order to have an on time departure.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.