Date: 201703
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Main Gear Door
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion; Distraction; Troubleshooting; Workload
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew; Person Maintenance
When detected: Aircraft In Service At Gate
Result: General Maintenance Action; General Release Refused / Aircraft Not Accepted
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: The off going crew briefed us on a CDL write-up for the left main landing gear center and inner door being removed. It was on the Release and also entered into the performance data and the landing data page within ACARS. We confirmed this on preflight. We flew the aircraft to [an intermediate airport] then on to our [destination]. After deplaning the Passengers the Gate Agent came to the cockpit and asked me if I knew there were Maintenance Personnel working under the aircraft. They had told her not to board and that the aircraft may be taken out of service. I said I had no knowledge of it and that I had not called Maintenance. I went down to the ramp and asked them what the issue was and they said Maintenance Control wanted the CDL re-evaluated and that the aircraft may be taken out of service. They said they would let me know. I went back upstairs and called our Dispatcher. He had no knowledge but after looking at his computer he confirmed the aircraft was on a Maintenance lock. He said he would call the Supervisor and get back to me. The Maintenance Personnel never came up to the jet way and said anything to me. Instead the Agent came back down a few minutes later and said the aircraft was being taken out of service and we would be swapping. As I was packing up; the Dispatcher called me back and confirmed the swap and that we should head [to another gate]. Our aircraft was there and ready to go. I asked him what Maintenance had found and he said they had said the damage to the landing gear was out of limits. I said we had just flown this aircraft for two legs and wondered out loud to him if it had even been legal. He said that might be a good question for the Chief Pilot on Call. I went to the next aircraft and called him back and he patched me through to the Chief. I briefed him on my concern that we had flown an aircraft for two legs that was now deemed not airworthy and expressed my concern that no one had met me [upon arrival] to brief me on this and that they had just started working on their inspection. He agreed this was a strange situation and recommended a report. Obviously Maintenance Control had been in touch with local Maintenance but did not bring Dispatch into the loop. I wonder; at what point after we took the aircraft did someone determine this damage might be out of limits and that it should be re-evaluated? Why was I allowed to [complete a previous leg] then on to a Maintenance base if there was some question as to the airworthiness? When the damage was determined to be out of limits and I learned of it; I immediately felt as if something had gone wrong here and I had taken an aircraft into the air that perhaps should not have been in service. I feel that someone wanted to 'quietly' evaluate the aircraft [upon arrival]; and if it was deemed to be in limits we would have been allowed to depart. That was not the case. As Captain why didn't Maintenance consult with me when I arrived? Why was the Dispatcher never informed by Maintenance Control of the issue? Did I fly a non-airworthy aircraft for two legs? The CDL only covered the missing gear doors. No mention was ever made of further damage to the aircraft. After Maintenance measured the damage and sent pictures to [the maintenance base] it was quickly determined the aircraft was not airworthy.




Synopsis: A B737NG Captain reported the left main landing gear doors were removed and a CDL documented in the maintenance log. After two legs maintenance removed the aircraft from service because after the fact; the damage was determined to be out of limits.