Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
General Maintenance Action
Human Factors
Checking the Aircraft Maintenance Log (AML) I noticed the aircraft had been written up multiple times for crew oxygen leaking. Yesterday the Captain's oxygen mask and smoke goggle equipment box was removed and replaced from aircraft to repair a suspected oxygen leak. This morning when testing the crew oxygen mask communications microphone it failed to transmit anything spoken. Called maintenance and we troubleshot the issue. I had the First Officer double check his mask and I also checked the observer's mask and both of them worked fine. Contract maintenance came out and found that the repairs made the day prior were incomplete and the maintenance personnel failed to connect the cannon plug to backside of the emergency oxygen mask. Had we or previous crews had an emergency with smoke or fumes in the cockpit we would have been unable to establish communication with each other. Captain would not have been able to speak with ATC as microphone was not hooked up.Maintenance needs to follow maintenance manual procedures/diagrams when putting aircraft back together and a full functionality check of the entire affected system once repair is complete to ensure next crew has an airworthy and safe aircraft.
CRJ-900 Captain reported he noticed during preflight that his crew oxygen mask had been serviced improperly and he would not have been able to communicate using it.