Date: 201212
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Pressurization Control System
Reporter organization: Air Carrier
Reporter function: Lead Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; General Maintenance Action
Contributing factors: Human Factors; Incorrect / Not Installed / Unavailable Part; Aircraft
Primary problem: Human Factors

Narrative: Before the aircraft arrived; Maintenance Control advised us that Aircraft X will arrive with pressurization issues. I was the Lead [Mechanic] in charge during the overnight shift. I assigned two technicians to remove the controller from Aircraft Y; also an A320; which was Aircraft Out of Service (AOS) in ZZZ in preparation for the arrival of Aircraft X. The Aircraft Maintenance Manual (AMM) reference [Chapter] (21-31-34) for the Cabin Pressure Controller (CPC) was printed from Airnav [Airbus Manual]. The CPC and Pack Temperature (Temp) Controller (PTC) were located next to each other in the Forward Electronic Compartment. The placard identifier next to each controller had the Number Two [#2] written and it was taken for granted that the part was the correct part that was removed without realizing that it was the incorrect part. I told the Technician to remove the CPC and the PTC was removed instead; without realizing. The Technicians may have misunderstood exactly what part was to be removed. I went to the flight deck and debriefed the flight crew and told the technicians that I will pull the Circuit Breakers (C/B) and let them know when it would be safe to replace the controller on Aircraft X. They installed the part and I proceeded to perform the Operational (Ops) Check per the AMM. The Ops Check passed and no CTC faults were present. Since the controller had an intermittent fault; it was not currently faulting. I also ran both engines per Maintenance Control's request to verify that no faults returned after [electrical] power swap. All checked OK. I verified the effectivity of the CPC before Aircraft X arrived and it was effective to both Aircraft X and Y. However; the incorrect part was removed from Aircraft Y; that was located next to the CPC and that part was not effective for Aircraft X. I was made aware of the configuration issue after aircraft departed.

Callback: Reporter stated that Aircraft X did not actually have a cabin pressurization issue; but a fault issue that appeared after engine starts at the previous departure station. Even though the Cabin Pressure Controller (CPC) was not removed and replaced; the original fault did not recur after he performed the engine runs. He decided to sign-off the discrepancy because there is only one sign-off block in the logbook and multiple technicians had been working the aircraft. The aircraft later diverted to another airport for continuing cabin pressurization faults. That's when their downline Maintenance technicians noticed the PTC was mistakenly replaced with a similar PTC part that was not effective for that A320. They also realized the CPC was never actually replaced. The PTC and CPC are physically different in size; but located next to each other with 'Control' labeled on the electronics rack for both controllers.



Synopsis: A Line Lead Mechanic explains how a Pack Temperature Controller (PTC) was removed and replaced (R/R) instead of a Cabin Pressure Controller (CPC) for cabin faults appearing after engine starts on an A320 aircraft. Aircraft later diverted after incorrect part replaced.