Date: 201507
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Cowling/Nacelle Fasteners; Latches
Component problem: Design
Reporter organization: Air Carrier
Reporter function: Inspector
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft; Procedure; Human Factors
Primary problem: Ambiguous

Narrative: An A check was being performed and completed on the [next] morning. The aircraft had some remaining open discrepancies; so the aircraft was finished up and released on the [following] morning. Upon the aircraft leaving it had its RH engine upper nose cowl come loose and depart the aircraft.The mechanic working the engines that night had me take a look before closing to ensure all tools rags and equipment was removed. At that time I went back to the office to complete my paperwork and paperwork/aircraft book closing responsibilities. Approximately 30-45 minutes later I went back out to do my walk around to see it closed up. I walked around to ensure all panels; latches; and cowls were closed up. Then I went on the staircase and took a peek up top to ensure the cowls were installed and no tools and equipment were left on top of the aircraft. Then the aircraft got towed outside to complete ops checks and engine runs. The aircraft was towed back in after completion to check the engines for leaks. No leaks were noted; the lower core cowls were open then closed back up. I did a final walk past to ensure the core cowls have been closed.Viewing the upper cowls from the portable staircase provides a good visual to see that the cowls are installed. But not for a detailed visual check of fasteners.  From that location the cowls appeared to be installed and had no obvious defect. Would need to do a detailed visual check of all the fasteners and not that just the cowls are installed.


Second narrative: I was working on the RH engine doing an inspection and servicing. Part of the task was to remove the upper and lower nose cowls. After performing all scheduled and unscheduled maintenance on the engine; I reinstalled both the upper and lower nose cowls as required. I reinstalled all of the required fasteners and then had the installation verified by an inspector. The aircraft did not leave until [2 days later]. Shortly after takeoff; the pilot had to shut down the RH engine and upon landing it was found that the upper nose cowl had departed the aircraft and the lower nose cowl was severely damaged as well as other area of the engine and tail. This part of the aircraft has a long history of failure. The FAA has issued an Airworthiness Directive (AD) to modify the nose cowls to strengthen and prevent these incidents from happening. This AD was performed on this aircraft and yet it still failed. I installed all of the hardware; which was verified and yet it still failed. I think that maybe there should be a more stringent verification process. Maybe after installing the nose cowls another mechanic or lead should verify the installation before going to the inspector. This would provide at least a third set of eyes before dispatching the aircraft. I know that this is what I will be doing; as well as maybe taking pictures of the installation.


Synopsis: A Maintenance Technician and Inspector describe the events that led up to the loss of engine upper cowling from CRJ-200.