Date: 201403
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Light: Night
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Minimum Equipment List (MEL)
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness; Time Pressure; Distraction
Second reporter function: Other / Unknown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
Detector: Person Maintenance
When detected: Other Post Departure
Result: General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft; Human Factors; MEL
Primary problem: MEL

Narrative: In ZZZ at the gate; when I got to the gate the Captain and Flight Attendants were all ready there. I found out that Maintenance was on the CRJ-200 aircraft. Maintenance was working on the left engine cowl anti-ice pressure relief valve and on the left thrust reverser; both on the left side. The left engine cowl anti-ice pressure relief valve had already been deferred on an earlier flight I believe? Maintenance came up and said that they deferred the left thrust reverser. We started to board while the Captain took a look at the MEL and I was working on ATIS; PDC; Weight and Balance. The aircraft had at least four or five MEL's that the Captain had to look at after Maintenance got the logbook back to the flight deck. We missed the one line that said both of these [MELs] cannot be deferred at the same time on the same side. The people who where involved was Maintenance; Captain and the First Officer. [Recommendations] for avoiding a recurrence of this event should be the get everyone to take more time; at this point we where already an hour or so late. We should have held off on boarding for five minutes; to take more time to look over the MEL and talk to Maintenance; to make sure everything with all the MEL's was OK. Five minutes would have made all the difference. It seemed [the MEL discrepancy] was detected by Maintenance the day after the event occurred. Maintenance called the Captain who then told myself (First Officer).


Second narrative: Shortly after arriving work; I put the thrust reversers on MEL; not knowing that the pressure relief valve MEL was associated. The pressure relief valve was put on MEL earlier in the day. I put the thrust reversers on MEL and the MEL book has nothing about the pressure relief valve being related to the thrust reverser under the thrust reverser MEL. Recommend the thrust reverser MEL should have a 'Note' about the relation to pressure relief valve.


Synopsis: A First Officer and Maintenance Controller report how a left engine thrust reverser MEL deferral was inadvertently applied to a CRJ-200 aircraft that already had the left engine cowl anti-ice pressure relief valve deferred. Contributing factor was the lack of any cross-reference information in the thrust reverser MEL section that deferral of both items on the same side of aircraft; was not allowed.