Date: 201909
Local time of day: 0601-1200
Location: TYS.Airport, TN
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Main Gear Wheel
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
Detector: Person Flight Crew
When detected: Pre-flight; Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Procedure; Incorrect / Not Installed / Unavailable Part; Logbook Entry; Human Factors
Primary problem: Incorrect / Not Installed / Unavailable Part

Narrative: I was the First Officer scheduled to operate. While briefing with the Captain at the flight deck and getting ready for the flight; 2 mechanics showed up at the flight deck to notify us about a rock puncture in the left number one main tire and needed to replace them. They took the aircraft logbook and they proceed to replace the tire. After about 45 minutes they returned the aircraft back to service with the proper logbook entries including MCN numbers and all proper signatures and told us the flight crew that everything was ready to go. All normal procedures were followed from departure to destination airport; uneventful flight. Next day; while performing some service checks due to prior maintenance issues with the anti-ice panel replacement due to the windshield heaters not working and generating master cautions; I got notified by Dispatch and my Captain that we took off the previous day and operated in an unsafe/not airworthy condition due to Maintenance [forgetting] to install a washer in the main gear that was replaced due to the rock puncture. I got in contact along with the Captain and the company Dispatch/Maintenance and they found the washer with [Company] Airlines' maintenance team in TYS Airport. The washer was later installed by [another Company] Maintenance Technician and the aircraft was returned to service in accordance to proper airworthiness FAR's and company procedures. As a pilot I am not trained to be a mechanic; therefore [it] is not possible for me to certify and/or tell 100% if Maintenance accomplished the proper work when replacing the left main tire. I can just do a visual inspection and rely in their suggestions and their verdict and their signatures certifying the plane is in a safe condition to return to service. Maintenance technicians should not be complacent and since they work in teams of two when it comes to problems like this they should keep the pilots in the loop and brief them appropriately even if it includes delaying the flight. Also; I believe the technicians should have a training were they double check their partner work in order to have more eyes into the same situation and avoid another situation like this.


Second narrative: [Report narrative contained no additional information.]


Synopsis: CRJ-200 flight crew reported that a washer was not installed after a main tire and wheel assembly was replaced; causing aircraft to be operated while un-airworthy.