Date: 201305
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Light: Night
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Parked
Aircraft component: Door Warning System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Avionics; Maintenance Powerplant
Human factors: Communication Breakdown; Distraction; Situational Awareness; Time Pressure; Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: B757-200 arrived ZZZ inbound with pilot write-up [referencing] Chapter 34-41; Weather Radar failed enroute. My partner and I reviewed the history before arriving at the aircraft. We noted several Weather Radar discrepancies within last 90 days. Began Troubleshooting (T/S) with Operational (Ops) Check and noted Weather Radar (Wx Rdr) did not perform full sweep in Test Mode. The sweep was only about 30-degrees of display on the right side of the display. Annunciations were: initially; Wx Rdr Test; followed by Wx Rdr fail. My partner went down to BITE Test the Radar Receiver/Transmitter (R/T) and noted that the BITE Test was inconclusive. There were no LEDs illuminated when he first viewed the front face of the R/T. The BITE function only tests the operation of the front face LEDs. At that time we ordered a Wx Rdr R/T. My partner swapped the R/T. Wx Rdr still failed the Ops Check. We ordered Wx Rdr Control panel since that is the only part that hasn't been changed and seemed logical due to Mode issues and Tilt issues in the aircraft's history. While waiting on control panel to arrive; we discussed reinstalling the original R/T which I then did. This led to a discussion about the history of the R/Ts; since several had been changed within the last 90 days. We proceeded back to the flight deck to review the history again; to verify the part number history of the installed R/T. The Control panel arrived; I went down and retrieved the control panel and went back to the flight deck to change it. We Ops tested the Wx Rdr again with no improvement in the discrepancy. I swapped the control panels back so that the original panel was reinstalled. We then decided to MEL the Wx Radar System due to lack of time to continue T/S. My partner called Maintenance Control and obtained MEL. Applied the MEL sticker; completed the aircraft logbook exception and left the MEL and the logbook open; on the First Officer's glareshield so the crew could review the logbook and MEL during their preflight. We turned the IRUs off and checked the flight deck; and walked back down to the truck to secure our tools and the parts we had ordered. We then called the Lead [Mechanic's] Office to inform them of what had occurred. The Lead Office acknowledged and informed us to return to the [Maintenance] Shop. While attempting to repair a broken Wx Rdr System with history; my partner and I were distracted by several factors: the area illumination light in the Forward Nose Compartment was out. We had to work by secondary lighting (headlamps). The Aircraft Service Attendant had issues closing the Lavatory Service Door and distracted my partner; asking him to assist in closing the door. This resulted in my partner advising him to call Line Maintenance to close the door. Also worth noting; the Door Indication System on the aircraft has a faulty nose compartment door switch. The flight deck indication was absent for this door being open. The Door Indication System was deferred after the aircraft returned to the gate. These are the conditions which I feel contributed to my involvement in this incident. However; I cannot account for the flight crew walk around or the pushback crew dispatching the aircraft. Looking back; I feel these were contributing factors leading to my distraction. I realize it was a major oversight to leave an access door open. It is not my intention to Dispatch an aircraft in an un-airworthy condition. [Recommend] focus on the task at hand. Avoid distractions to the extent possible. Use the Maintenance Manual (M/M) as a checklist and ensure all steps are addressed/checked-off before departing the aircraft. Air turnback.




Synopsis: An Avionics Technician describes some of the factors that contributed to a B757-200 air turnback with the Forward Nose Compartment access door still open. He had been troubleshooting the Weather Radar System and no one realized the Nose Compartment Door Indication System switch had failed prior to departure.