Narrative:

Aircraft was dispatched with the L-1 door warning system on placard. The problem was a nasty repeating one with weeks of write-ups and honest troubleshooting/parts replacement. As we started the takeoff roll; at approximately 30 KTS; we got a master caution (yellow light). Looking around I saw that it was the door annunciator for the L-1 door. As the first officer was hesitating in the continuation of the takeoff roll; I told him 'it's just the door; go; go; go.' we continued the takeoff with the door light cycling on and off at various speeds finally ceasing out of 7000 ft. I feel that the application of the MEL was well intentional but inexact. The warning system worked; ie; if the door opened; the light came on reliably. The problem was the warning light would cycle on its own. Such action could prompt an abort; which is a high risk maneuver. This is an unforeseen consequence of using this MEL item when the system is malfunctioning as this one was. In my opinion; the MEL was written for a total failure of the warning light. Such application would be proper and safe. The application of this MEL in this case however was a set-up for a potential disaster. We operated 2 legs on long; clean; dry runways; which allowed us the luxury of time dealing with the false warning. On a poor; ie; short/contaminated runway; the results would have probably been an abort. What wasn't recognized was the linkage of the erroneous warning with the master warning system and its effects on pilot actions. I suggest the scope of this MEL item be restr to total system failure; not partial as was this case. Callback conversation with reporter revealed the following information: reporter stated his concerns about his company's MEL maintenance procedure allowing the deferral of a cabin door warning system light as 'inoperative;' when in fact; the door annunciator light continued to flicker 'on' and 'off' during takeoff roll and at cruise. This has also triggered the master caution light each time. No procedures exist in the MEL for maintenance to open and collar a C/B to actually disarm the erratic annunciator light. The current MEL procedure creates an environment of confusion and distraction during critical operational periods. Reporter adds; if the system is deferred as 'inoperative;' then that system should actually be 'inoperative;' and not be allowed to continue flashing erratic and unreliable warnings. Door lights are illuminated on the overhead annunciator panel not on his EFIS system fwd display. Reporter also stated his maintenance control says they have been chasing the cause of the erratic door indication for two weeks. Door proximity switches have been changed several times. Maintenance suspects wire bundle is the issue.

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Original NASA ASRS Text

Title: A B737-800 CAPTAIN REPORTS OF CONCERNS ABOUT MAINT DEFERRING AS 'INOP' THE DOOR 1-LEFT OVERHEAD ANNUNCIATOR LIGHT THAT WOULD CONTINUE TO ILLUMINATE ON ITS OWN; TRIGGERING THE MASTER CAUTION LIGHT DURING TKOF ROLL AND AT CRUISE.

Narrative: ACFT WAS DISPATCHED WITH THE L-1 DOOR WARNING SYS ON PLACARD. THE PROB WAS A NASTY REPEATING ONE WITH WKS OF WRITE-UPS AND HONEST TROUBLESHOOTING/PARTS REPLACEMENT. AS WE STARTED THE TKOF ROLL; AT APPROX 30 KTS; WE GOT A MASTER CAUTION (YELLOW LIGHT). LOOKING AROUND I SAW THAT IT WAS THE DOOR ANNUNCIATOR FOR THE L-1 DOOR. AS THE FO WAS HESITATING IN THE CONTINUATION OF THE TKOF ROLL; I TOLD HIM 'IT'S JUST THE DOOR; GO; GO; GO.' WE CONTINUED THE TKOF WITH THE DOOR LIGHT CYCLING ON AND OFF AT VARIOUS SPDS FINALLY CEASING OUT OF 7000 FT. I FEEL THAT THE APPLICATION OF THE MEL WAS WELL INTENTIONAL BUT INEXACT. THE WARNING SYS WORKED; IE; IF THE DOOR OPENED; THE LIGHT CAME ON RELIABLY. THE PROB WAS THE WARNING LIGHT WOULD CYCLE ON ITS OWN. SUCH ACTION COULD PROMPT AN ABORT; WHICH IS A HIGH RISK MANEUVER. THIS IS AN UNFORESEEN CONSEQUENCE OF USING THIS MEL ITEM WHEN THE SYS IS MALFUNCTIONING AS THIS ONE WAS. IN MY OPINION; THE MEL WAS WRITTEN FOR A TOTAL FAILURE OF THE WARNING LIGHT. SUCH APPLICATION WOULD BE PROPER AND SAFE. THE APPLICATION OF THIS MEL IN THIS CASE HOWEVER WAS A SET-UP FOR A POTENTIAL DISASTER. WE OPERATED 2 LEGS ON LONG; CLEAN; DRY RWYS; WHICH ALLOWED US THE LUXURY OF TIME DEALING WITH THE FALSE WARNING. ON A POOR; IE; SHORT/CONTAMINATED RWY; THE RESULTS WOULD HAVE PROBABLY BEEN AN ABORT. WHAT WASN'T RECOGNIZED WAS THE LINKAGE OF THE ERRONEOUS WARNING WITH THE MASTER WARNING SYS AND ITS EFFECTS ON PLT ACTIONS. I SUGGEST THE SCOPE OF THIS MEL ITEM BE RESTR TO TOTAL SYS FAILURE; NOT PARTIAL AS WAS THIS CASE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED HIS CONCERNS ABOUT HIS COMPANY'S MEL MAINT PROCEDURE ALLOWING THE DEFERRAL OF A CABIN DOOR WARNING SYSTEM LIGHT AS 'INOP;' WHEN IN FACT; THE DOOR ANNUNCIATOR LIGHT CONTINUED TO FLICKER 'ON' AND 'OFF' DURING TKOF ROLL AND AT CRUISE. THIS HAS ALSO TRIGGERED THE MASTER CAUTION LIGHT EACH TIME. NO PROCEDURES EXIST IN THE MEL FOR MAINT TO OPEN AND COLLAR A C/B TO ACTUALLY DISARM THE ERRATIC ANNUNCIATOR LIGHT. THE CURRENT MEL PROCEDURE CREATES AN ENVIRONMENT OF CONFUSION AND DISTRACTION DURING CRITICAL OPERATIONAL PERIODS. REPORTER ADDS; IF THE SYSTEM IS DEFERRED AS 'INOP;' THEN THAT SYSTEM SHOULD ACTUALLY BE 'INOP;' AND NOT BE ALLOWED TO CONTINUE FLASHING ERRATIC AND UNRELIABLE WARNINGS. DOOR LIGHTS ARE ILLUMINATED ON THE OVERHEAD ANNUNCIATOR PANEL NOT ON HIS EFIS SYSTEM FWD DISPLAY. REPORTER ALSO STATED HIS MAINT CONTROL SAYS THEY HAVE BEEN CHASING THE CAUSE OF THE ERRATIC DOOR INDICATION FOR TWO WEEKS. DOOR PROXIMITY SWITCHES HAVE BEEN CHANGED SEVERAL TIMES. MAINT SUSPECTS WIRE BUNDLE IS THE ISSUE.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.