Date: 201405
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: IMC
Weather elements / visibility: Turbulence
Aircraft: A300
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Other / Unknown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Declared Emergency
Contributing factors: Chart Or Publication; Human Factors
Primary problem: Human Factors

Narrative: During climbout; passing FL260; we received an ECAM alert 'Air Pack Fault'. Both packs had tripped off. I flew the aircraft while the First Officer complied with the ECAM and checklist procedures. We were unable to bring the packs back online and therefore initiated a descent. When the cabin altitude reached 10;000; we donned our oxygen masks and declared an emergency. RTB un-eventful. The APU master switch and APU bleed we're not turned off prior to departure. While working the problem at altitude; we failed to notice the APU was still running. ECAM and checklist procedures did not address this contingency. QRH procedure should be modified to include APU operation as a potential factor in pack faults. Also; before takeoff; below the line could include the challenge 'memo page'; 'checked'.


Second narrative: During climbout passing FL260 we received an ECAM alert 'air pack fault' both packs had tripped off. Captain continued to fly the airplane and I complied with the ECAM and checklist procedure. We were not able to restore the packs which caused our cabin to climb. When the cabin alt reached 10;000 FT; we donned our oxygen masks and declared an emergency. We returned for an uneventful landing.The root cause of the problem was that I missed turning off the APU master switch and APU bleed switch when the Captain called for the After Start Checklist. I turned the Ignition Selector off and looked for the flowbars to change to green. The lighting in the cockpit was such that I could not tell if they were green or off. I put my hand up to shade the lights and thought they were green; in reality the pack flow bars were green and the bleed flow bars were off; however; they both looked the same. This broke my normal flow pattern. When I was working the ECAM my attention was focused on the amber pack lights and again I did not find my error. It was not until we started our descent and the packs came back on that I saw that I had not turned off the APU and the APU bleed switch. Better system training; it should be emphasized that making this error would result in a serious problem. Also; the QRH should have this as a note or part of the procedure to verify the APU bleed valve is not on.


Synopsis: A300 flight crew experiences an 'air pack fault' passing FL260 during climb. The QRH is not successful at correcting the problem and a descent is initiated and oxygen masks are donned. During descent the packs come back on and it is noticed that the APU is on and supplying the bleed source for both packs. An uneventful landing ensues.