Narrative:

I performed a bite check on the WX radar transceiver. Due to insufficient lighting the bite check display screen appeared to show no readout. I removed and replaced the WX radar transceiver per maintenance manual. With the use of a flashlight the bite check display showed an antenna fault. I removed and replaced radar antenna assembly and performed an operational check for the WX radar system per the maintenance manual and the system checked good. Believing due to insufficient lighting; I reinstalled the original WX radar transceiver and again performed another operational check on the WX radar system which also checked good per maintenance manual. During reinstallation of WX radar transceiver the pneumatic connector of the #1 air data module (adm) was not properly installed. Per the maintenance manual a warning states failure to connect this hose will result in captain's loss of air data. A note is also shown to verify a blue band is visible to ensure a positive lock of the connector. The blue band was visible to myself and I released the aircraft for service. During climb out the captain experienced total loss of #1 air data system and air turned back to ZZZ. I returned to the airplane and inspected #1 adm pneumatic connector and observed the line attached; but was not locked. I secured the pneumatic connector performed an operational check of the #1 air data system and the aircraft was returned to service and continued on a later flight with no further incident. Being certain I had seen a visible blue band during my installation; I tried to attach the pneumatic connector in a position where the blue band is visible but not locked. The thickness of the blue band visible when a positive lock is achieved is approximately 1/4 of an inch. There is a possible scenario if the connector tangs are resting directly center of the locking studs of the adm a blue band of less than 3/16 of an inch is visible. If I had used a flashlight to read the WX radar transceiver bite display screen I probably would not have replaced the WX radar transceiver. Due to my lack of attention; I should have used sufficient lighting to verify the locking tangs of the pneumatic connector were engaged instead of relying on the blue band. A simple pull of the pneumatic line would have caused the line to become disconnected preventing the improper installation and this incident.

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Original NASA ASRS Text

Title: A B737 ACFT REQUIRED AIR TURN BACK AFTER TOTAL LOSS OF CAPTAIN'S #1 AIR DATA SYS; DUE TO IMPROPER INSTALLATION.

Narrative: I PERFORMED A BITE CHK ON THE WX RADAR TRANSCEIVER. DUE TO INSUFFICIENT LIGHTING THE BITE CHK DISPLAY SCREEN APPEARED TO SHOW NO READOUT. I REMOVED AND REPLACED THE WX RADAR TRANSCEIVER PER MAINT MANUAL. WITH THE USE OF A FLASHLIGHT THE BITE CHK DISPLAY SHOWED AN ANTENNA FAULT. I REMOVED AND REPLACED RADAR ANTENNA ASSEMBLY AND PERFORMED AN OPERATIONAL CHK FOR THE WX RADAR SYS PER THE MAINT MANUAL AND THE SYS CHKED GOOD. BELIEVING DUE TO INSUFFICIENT LIGHTING; I REINSTALLED THE ORIGINAL WX RADAR TRANSCEIVER AND AGAIN PERFORMED ANOTHER OPERATIONAL CHK ON THE WX RADAR SYS WHICH ALSO CHKED GOOD PER MAINT MANUAL. DURING REINSTALLATION OF WX RADAR TRANSCEIVER THE PNEUMATIC CONNECTOR OF THE #1 AIR DATA MODULE (ADM) WAS NOT PROPERLY INSTALLED. PER THE MAINT MANUAL A WARNING STATES FAILURE TO CONNECT THIS HOSE WILL RESULT IN CAPT'S LOSS OF AIR DATA. A NOTE IS ALSO SHOWN TO VERIFY A BLUE BAND IS VISIBLE TO ENSURE A POSITIVE LOCK OF THE CONNECTOR. THE BLUE BAND WAS VISIBLE TO MYSELF AND I RELEASED THE ACFT FOR SVC. DURING CLBOUT THE CAPT EXPERIENCED TOTAL LOSS OF #1 AIR DATA SYS AND AIR TURNED BACK TO ZZZ. I RETURNED TO THE AIRPLANE AND INSPECTED #1 ADM PNEUMATIC CONNECTOR AND OBSERVED THE LINE ATTACHED; BUT WAS NOT LOCKED. I SECURED THE PNEUMATIC CONNECTOR PERFORMED AN OPERATIONAL CHK OF THE #1 AIR DATA SYS AND THE ACFT WAS RETURNED TO SVC AND CONTINUED ON A LATER FLT WITH NO FURTHER INCIDENT. BEING CERTAIN I HAD SEEN A VISIBLE BLUE BAND DURING MY INSTALLATION; I TRIED TO ATTACH THE PNEUMATIC CONNECTOR IN A POS WHERE THE BLUE BAND IS VISIBLE BUT NOT LOCKED. THE THICKNESS OF THE BLUE BAND VISIBLE WHEN A POSITIVE LOCK IS ACHIEVED IS APPROX 1/4 OF AN INCH. THERE IS A POSSIBLE SCENARIO IF THE CONNECTOR TANGS ARE RESTING DIRECTLY CTR OF THE LOCKING STUDS OF THE ADM A BLUE BAND OF LESS THAN 3/16 OF AN INCH IS VISIBLE. IF I HAD USED A FLASHLIGHT TO READ THE WX RADAR TRANSCEIVER BITE DISPLAY SCREEN I PROBABLY WOULD NOT HAVE REPLACED THE WX RADAR TRANSCEIVER. DUE TO MY LACK OF ATTN; I SHOULD HAVE USED SUFFICIENT LIGHTING TO VERIFY THE LOCKING TANGS OF THE PNEUMATIC CONNECTOR WERE ENGAGED INSTEAD OF RELYING ON THE BLUE BAND. A SIMPLE PULL OF THE PNEUMATIC LINE WOULD HAVE CAUSED THE LINE TO BECOME DISCONNECTED PREVENTING THE IMPROPER INSTALLATION AND THIS INCIDENT.

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.