Narrative:

Reference fom 3.1.17/18. This section says that it is not necessary for all of the 'scoreboard' lights to illuminate for a successful test of the master caution lights. I have found this to be incorrect. I have found that on several of our aircraft; if you perform a recall test of the system and the opposite side 'scoreboard' is not fully engaged in place (as often happens when a pilot tests the system and allows the light panel to snap back after the test); then the master caution annunciator light does not illuminate even though an overhead system light is on. This could lead to the unlikely; but possible; scenario of a flight crew being unaware of a system malfunction. For example: if a hydraulic pump 'low pressure' light is illuminated on the overhead panel and the first officer side scoreboard is unseated far enough that the hydraulic light will not illuminate; then depressing the captain side scoreboard to perform the recall test does not illuminate the yellow 'master caution' light. I have found this to be true on the following aircraft (8 aircraft numbers). My unscientific testing seems to show that this is true on about 20-25% of our fleet. I believe that the fom should be changed to emphasize that when a recall test is performed that all of the scoreboard as well as the master caution lights should illuminate then extinguish.

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Original NASA ASRS Text

Title: A B737-700 CAPT RPTS CONFLICT BTWN FOM MASTER CAUTION LIGHT TEST AND ACTUAL TEST OF CAUTION LIGHT SYS.

Narrative: REF FOM 3.1.17/18. THIS SECTION SAYS THAT IT IS NOT NECESSARY FOR ALL OF THE 'SCOREBOARD' LIGHTS TO ILLUMINATE FOR A SUCCESSFUL TEST OF THE MASTER CAUTION LIGHTS. I HAVE FOUND THIS TO BE INCORRECT. I HAVE FOUND THAT ON SEVERAL OF OUR ACFT; IF YOU PERFORM A RECALL TEST OF THE SYS AND THE OPPOSITE SIDE 'SCOREBOARD' IS NOT FULLY ENGAGED IN PLACE (AS OFTEN HAPPENS WHEN A PLT TESTS THE SYS AND ALLOWS THE LIGHT PANEL TO SNAP BACK AFTER THE TEST); THEN THE MASTER CAUTION ANNUNCIATOR LIGHT DOES NOT ILLUMINATE EVEN THOUGH AN OVERHEAD SYS LIGHT IS ON. THIS COULD LEAD TO THE UNLIKELY; BUT POSSIBLE; SCENARIO OF A FLT CREW BEING UNAWARE OF A SYS MALFUNCTION. FOR EXAMPLE: IF A HYD PUMP 'LOW PRESSURE' LIGHT IS ILLUMINATED ON THE OVERHEAD PANEL AND THE FO SIDE SCOREBOARD IS UNSEATED FAR ENOUGH THAT THE HYD LIGHT WILL NOT ILLUMINATE; THEN DEPRESSING THE CAPT SIDE SCOREBOARD TO PERFORM THE RECALL TEST DOES NOT ILLUMINATE THE YELLOW 'MASTER CAUTION' LIGHT. I HAVE FOUND THIS TO BE TRUE ON THE FOLLOWING ACFT (8 ACFT NUMBERS). MY UNSCIENTIFIC TESTING SEEMS TO SHOW THAT THIS IS TRUE ON ABOUT 20-25% OF OUR FLEET. I BELIEVE THAT THE FOM SHOULD BE CHANGED TO EMPHASIZE THAT WHEN A RECALL TEST IS PERFORMED THAT ALL OF THE SCOREBOARD AS WELL AS THE MASTER CAUTION LIGHTS SHOULD ILLUMINATE THEN EXTINGUISH.

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.