Date: 201510
Local time of day: 0601-1200
Location: ZZZ.TRACON, US
Flight conditions: VMC
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Cargo Compartment Fire/Overheat Warning
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Troubleshooting; Distraction
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Diverted; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft; Manuals
Primary problem: Aircraft

Narrative: We were beginning day three of the trip. We got to the airplane; performed our preflight duties to begin our trip. There was one outstanding maintenance issue that was being looked at and corrected. We pushed 18 minutes late due to the maintenance discrepancy and waited approximately another 45 minutes for departure. I was the Pilot Flying. Weather was day VMC. We were given a heading and told to contact departure. We cleaned the aircraft up and the After Takeoff Checklist was completed. Upon contacting departure control; were given instructions to climb to 10;000 feet and turn to a heading of 360. We were climbing through 3;000 feet when we were alerted by the CRC (Continuous Repetitive Chime) and an ECAM indication of an AFT CARGO FIRE. I leveled off the aircraft. Departure subsequently gave additional instructions at which time I [contacted ATC] stating the nature of our [situation]. We began the Non Normal Methodology to deal with this fire indication. After looking to see if it was an Immediate Action Item or ECAM Exception we began to complete the ECAM Actions. When our attention was to begin to deal with the fire; the ECAM had changed to SMOKE AFT CARGO DETECTION FAULT. We followed with Non Normal Methodology and completed the checklist and noted it was a Crew Awareness item. We began to evaluate this situation and told ATC that our condition did not appear as dire and we wanted to consult with company and maintenance. Upon their response that it was probably a CIDS malfunction and in agreement between Dispatch and my First Officer (FO); I elected to continue.There had been history on this aircraft just 3 pages back of this SMOKE AFT CARGO DETECTION FAULT. After things had settled down; my FO and I discussed this issue a little more and he noted that we had no Aft Cargo Smoke Detection anymore. It was at this point I did call [to commercial radio] with dispatch and I told them we were going to divert because of that lack of detection. We went through the Overweight Landing Checklist; the landing was virtually a non event and all items of concern were entered into the AML. Maintenance found that one of the smoke detectors had gone bad. We were removed from the trip as the time to repair was going to exceed our duty day.I have since had time to think and review this issue. First and foremost; there is no AFT CARGO FIRE ECAM in our checklist or manuals. We only have SMOKE FWD (AFT) CARGO SMOKE. Both of us read the ECAM indication and I stated it verbally AFT CARGO FIRE. We both agreed with the condition. Why would an issue with a smoke detector failing cause a false indication to give a fire condition. Something is not right. Either the programming is not correct and/or the program verbiage is not right. This was a very disconcerting event. At no time does any pilot want to be confronted with fire; but most assuredly a false condition causing a fire indication due to a failure of a cargo smoke detector is appalling. I have talked with those that are very familiar with the Airbus 320 family and it was stated to me that this is a rare occurrence with the Airbus; but it does happen. We absolutely need answers on this event; as I don't want any other pilot to experience an event such as this.


Second narrative: After flap retraction around 3;000 feet MSL; we got a CRC and lower ECAM warning. My best recollection was it had the words; 'AFT CARGO' and 'FIRE'. The warning was red for sure. I was pilot monitoring. I silenced the CRC; the captain noticed the ECAM at the same time and leveled the AC at 3;000 feet MSL. I heard him [notify ATC of the situation]. I checked the QRH to see if it was an Immediate Action or ECAM Exception; it was not. The captain transferred the Pilot Flying (PF) duties to me. I alerted departure control to expect us to return for a landing as soon as possible after we ran through our procedures. He had us climb to 3;100ft MSL and gave us vectors around to the northwest of the airport. Within moments of this; before the captain could start the ECAM procedures; the red ECAM warning disappeared and was replaced by an amber caution 'SMOKE AFT CARGO DET FAULT'. We both recollected that there was a prior write up a few pages back in the log book pertaining to this ECAM message. I was still PF getting delay vectors while the captain was communicating with the company. My understanding was that the company determined that it was a CIDS problem and they were aware of it. We felt that we were cleared to continue. We [told ATC the situation was handled] and continued on our flight plan. As we were discussing the situation; we determined that we did not have any aft cargo fire detection. Upon reviewing the MEL book; we realized that the only way an aircraft can be dispatched without that system working was if the aft cargo compartment was empty. We decided that we had an unsafe condition and needed to land. The captain again conferred with the company and we diverted.Somehow; the faulty smoke detector gave a false warning before it showed faulted. Also; I am pretty sure (not 100% though) that I saw the word 'FIRE' in the ECAM warning. Upon reviewing the possible ECAM warnings; this is not a word that is used in the list of possibilities for the aft cargo set of ECAM messages.


Synopsis: Airbus A321 flight crew reported receiving an aural alarm and an 'AFT CARGO FIRE' ECAM alert which later became a 'SMOKE AFT CARGO DET FAULT'. The crew elected to divert and land as a precaution. There was confusion about the indications and checklist procedures as there is no procedure for 'CARGO FIRE'; only for 'CARGO SMOKE'.