Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Training / Qualification; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Human Factors
Operations manual sections X.Y.Z and X.Y.A; as well as Flight Attendant manual B.A.C call for the use of the flight deck doorbell as a preliminary step in the event the flight attendants are unable to contact the pilots on the interphone. This should not be confused with entering the emergency access code to unlock the flight deck door---that would be the next step. According to the manuals; pressing the doorbell code should activate the two-chime doorbell. Though not required; I check and demo the doorbell function during my Crew brief with each new Crew of Flight Attendants. Anecdotally; I would say about 20%-25% of our aircraft have inoperative doorbells as of a few months ago. More recently it seems to me the percentage of inop doorbells has lessened a bit.When I encounter an inoperative doorbell I write it up in the logbook. In my experience; almost all Maintenance personnel; almost all Pilots and almost all FAs are unaware the doorbell function exists and are unaware it is part of our procedures. Hence the high incidence of inoperative doorbells. No one knows they exist so no one checks. I would be willing to bet that most pilots; if they heard the two-chime doorbell in flight; would misidentify it as an entry of the flight deck emergency access code.Further; I was recently told by a Maintenance Tech that he believes the problem might be two-fold. First; our aircraft come from Boeing without the doorbell function programmed. The programming happens after company takes possession and makes the changes necessary to get the aircraft ready for revenue flight. So perhaps it is being missed there. Second; he said it is possible the doorbell program and/or code are dropped out of the flight deck emergency access panel during other periodic maintenance procedures. I realize it is not necessary that we all memorize the procedure; chapter and verse; for emergency access to the flight deck. That is what the manuals are for; but our manuals instruct our flight attendants to activate the doorbell to establish communication with the pilots before trying the emergency access code. If a significant number of our aircraft have inoperative doorbells; that is a problem. It is even more of a problem if no one is checking the functionality and more still if maintenance procedures are being missed or inadvertently deleting the code.I think we need to look at maintenance procedures closely to see where the problem might be occurring. Also; I think we need to address doorbell operation and what it sounds like compared to the continuous tone of the emergency access code; in both pilot training and flight attendant training. In the meantime; a training topic might be in order.
Air Carrier Captain reported the flight deck door chime systems are inoperative on several aircraft. During crew briefings the Captain found many crew members are unaware of the chime system and its operating characteristics.