B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 185; Flight Crew Total 12933; Flight Crew Type 2295
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Security
Flight Crew Became Reoriented; General Maintenance Action
Aircraft; Procedure
During preflight; the emergency access test of the flight deck Boeing door provided the wrong audio response.  Instead of getting the continuous horn for 30 seconds immediately; we receive the normal door entry response of 2 distinct momentary horns followed 20 seconds later by the normal entry signal of 2 tone again and then after an additional 20 seconds by the continuous 30 second horn.  The electronic lock worked normally and the emergency entry unlock did unlock the door eventually.   We were released with MEL 52-17.  This required us to deactivate the electronic locking function of the door and removed the ability for emergency access to the flight deck should the need arise.   This MEL 52-17 leaves the door unlocked electrically during the entire flight and requires a manual locking of the door.  Although this is allowed; it involves an addition step that is needed to be performed in a timely manner should the flight deck be rushed during an attempted breach.   Each flight attendant was instructed and actually performed these steps prior to our departure with the emphasis of the door being unlocked until turning the manual lock.   Upon further review; MEL 52-17-XX would have been the better deferral available for this defect of the key pad system.   It would have allowed us to have the electronic lock available to us the entire flight and the ability for emergency access from the cabin should the need arise.  A defect report was submitted during flight that a different MEL was more appropriate.  It was released with MEL 52-17-XX for subsequent flights.  I am very familiar with the Boeing flight deck door.  I have flown exclusively with this door system ever since we started using them.   In all my years; I have witnessed only one time it hasn't passed a check during preflight.  I almost never use this door since coming back to the 737 fleet 8 months ago.  This is disturbing since this is the 2nd time that I have seen this identical failure.  I am not even sure whether I have flown another aircraft (AC) with the Boeing door system since the last time I experienced this failure (a good month in between these flights).  This might be an issue requiring maintenance to do a system wide check of our Boeing doors.  Both times; I was released with the less desirable MEL 52-17.   Hopefully Maintenance Control will issue the MEL which provides the most safety features of the door in the future; ie MEL 52-17-XX. This malfunction presented itself exactly the same both times.  I cannot emphasis enough that this is an extremely high percentage of failures that I have personally witnessed.   I am not sure whether this is a programing; software; or faulty keypad issues.  This might be an extremely unlikely coincidence; but it could be a 737 system wide problem.  This needs to be addressed immediately by ensuring that all 737 crews performing this door test know the correct audio response.  Since this is a newer procedure for some crews; this defect may not be recognized.  Additionally some type of training might be needed for pilots and flight attendants to ensure proper Boeing door procedures.  We rarely get this door and it is a first flight only test.  There is a potential of this test not being performed.  I caught both of these defects while demonstrating the procedures and functions of the Boeing door to the Flight Attendant (FAs); although a test wasn't required.   I believe a test should be performed every time reporting to the AC.         Although this was not an issue on this flight.  The 737 fleet Boeing door procedures have crews turning on the Flight deck access switch during the flight deck security check and never turning it off when leaving the flight deck.  This differs significantly from previous Boeing door procedures that turn off and open the guard switch on the flight deck access switch when the flight deck is unoccupied on the ground and then to turn it on and engage the guard  cover when thecabin is reported ready prior to pushback.   I believe the 737 fleet should adopt these procedures to prevent being locked out of the flight deck on the ground and to reinforce the requirement to arm and ensure the 'Lock Fail' light extinguishes and the door is locked prior to pushback.  A very important step is being missed by not turning off the access switch after the test; once 'deny' has been selected the door is locked without anyway of entering the flight deck for 30 minutes.  This could cause not only embarrassment on the ground but safety issues as well.
B737 Captain reports that during preflight; the emergency access test of the flight deck Boeing door provided the wrong audio response. The door was deferred with the most restrictive MEL which the Captain believed was not the best choice.