Date: 201201
Local time of day: 1201-1800
Location: PHL.Airport, PA
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
ATC / advisory: Ramp PHL
Aircraft component: Oxygen System/Crew
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Check Pilot
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Time Pressure; Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: I was scheduled to fly one leg with a Captain upgrade candidate to complete an FAA observation for him that had been canceled earlier. Due to extraneous circumstances the original FAA observer was unable to do the checkride. The three of us arrived at the departure gate and awaited the arrival of the inbound aircraft. It was running about 20 minutes late. Once the passengers started to deplane; I went down the jetway to start my preflight duties. During the interior preflight we noticed that the oxygen level was below 1;410 PSI and the OXY LOW PRESS caution was posted. I had the First Officer call in the discrepancy and enter it in to the maintenance logbook. The line mechanics showed up to the airplane and serviced the oxygen to 'normal' levels and signed the logbook. The First Officer had mentioned to me that it had been written-up previously. I looked at the logbook and saw the write-up. After the maintenance action was completed; we boarded up and departed. While in cruise; we noticed the oxygen level was depleting. The Check Airman was in the jumpseat and asked to look at the logbook. He started to scrutinize all entries that related to oxygen. He discovered nine write-ups relating to oxygen servicing since Christmas. Upon completion of the flight; we observed the oxygen pressure had lost 220 LBS since servicing one hour before. The oxygen level was still above the caution level; but was getting close. We notified the outbound crew of our findings and observations; and they subsequently called maintenance. This is a tricky situation for us. We; as line pilots; don't determine airworthiness; but maintenance did us no favors by routinely servicing the oxygen. The oxygen had been serviced only hours before. There has to be some accountability on their end of this for a poor remedy to an obviously reoccurring problem. We probably should not have taken this airplane. I needed to do a more thorough review of the logbook. If I would have scrutinized each individual write-up better; I possibly would have noticed that it had not only been serviced that day; but exactly how many times it had been serviced in the recent past. Crew communication may have prevented this also. I should have approached the Captain that brought it in and asked some questions. All these oxygen systems vary a little. I assumed that the pressure drop was from the recent cold snap; since every aircraft I have been in the last two days had depleted oxygen levels. Complacency was a factor here. I need to remain vigilant all day every day.




Synopsis: A CRJ200 oxygen system repeatedly lost pressure and was serviced without anyone noticing the recurring leak until after the ninth service in less than a month.