Date: 202012
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Light: Night
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Airspace: Class B ZZZ
Aircraft component: APU Electrical
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Avionics; Maintenance Airframe; Maintenance Powerplant
Human factors: Fatigue; Distraction; Training / Qualification; Troubleshooting; Workload; Time Pressure
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Ground Event / Encounter Other / Unknown
Detector: Person Maintenance
Result: Aircraft Aircraft Damaged; Flight Crew Returned To Gate; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Procedure; Equipment / Tooling; Human Factors
Primary problem: Procedure

Narrative: Incident / Discovery: Maintenance work light / flash light found in the the nose landing gear wheel well which resulted in an air return of the aircraft.Aircraft location: Aircraft X B737-800 was located in the parking area at ZZZ Airport.Work Conditions: Night time; outside; no spot lighting or ambient lighting. Sky conditions clear. Temperature 30(s) Fahrenheit.On the night; Coworker and I were assigned to troubleshoot log X 'Unable to access APU bite' Per previous log entry of being suspect; I replaced the R735 relay in the J20 box; took us some time to locate the J20 box and the relay because the WDM and IPC were not clear on the exact location. 2-3 hours to locate on aircraft. This junction box is located behind the L/H rear pressure panel of the nose landing gear box structure. However; access was difficult to the box from the nose landing gear area due to the angle of access and aircraft height. In turn; I climbed into the E/E bay with a blue hand light; head lamp and a No. 2 Philips screw driver; maneuvered/positioned myself over the flight deck air supply duct along the left side of the nose wheel box structure to get better access to the J20 cover; Relay 735 and associated cannon plug for troubleshooting purposes. Coworker was in support from the nose landing gear wheel well to hand me various items I needed to work through the access structure.As documented in the log; the relay did not correct the issue so we continued to troubleshoot which required continuous access to the J20 box. I was mainly working from inside the E/E bay; not from the nose landing gear wheel well.As the night progressed and not finding any faults with the physical wiring; we reported to our lead where we were at. Was told that the aircraft is needed for a flight; document where we were at and close up the aircraft.We headed back out to the aircraft. When we got back to Aircraft X; I double checked the APU ECU security; checked the aft cargo bay for equipment and tools; closed the aft cargo bay door. I then proceeded into the E/E bay to secure the J20 box cover and check for security and check for tools and equipment. As I was doing this; Coworker was securing the nose landing gear wheel well pressure panel.After Coworker finished installing the panel; I went inside the flight deck to re-engage two circuit breakers and to pressurize the aircraft for the leak check of the pressure panel. Once pressurized; Lead performed the leak check of the pressure panel. When leak check was satisfactory; I depressurized the aircraft; powered down; closed the main cabin door and pulled the air stairs. Shortly after we met in the vehicle we had and began going over paper work.Coworker and I are somewhat new to avionics and have a lot to learn about the various differences between our fleet types and associated details of each. We are very capable of doing the work but would feel more comfortable to be paired with someone who is well seasoned in the avionics shop. It should be this way for anyone that is new. Since I have been in the shop; I have been paired mainly with inexperienced technicians who are learning the same way as I am; learn as you go. Common sense would dictate to pair a very experienced tech with a inexperienced tech; this promotes growth; development and prevents mistakes.I'm sorry that this unfortunate mistake took place and is an oversight I strive to never let happen; unfortunately it did. I will be much more vigilant in the future about tooling and equipment used for aircraft maintenance to make sure this will never happen on my end again.


Second narrative: My co-worker and I received our assignment to work on the Aircraft X located [in parking]; a remote maintenance area (ZZZ). I remember on that day I was closing up a pressure panel at the nose landing gear wheel well and the battery of the octagon light died on me and so I had to use my flash light. Because we have been outside for so long; I was in the rush to get back to the office; which in the process I left the light in the nose wheel well and also I forgot to double check all my tools and I take full responsibility for my actions. Co-worker and I are new to this bid area and every day we are been paired with new people to figure things out on our own. On the day of the event; the working area was pitch black; it was very cold outside; the AMM (Aircraft Maintenance Manual) was a little confusing; trying to locate this J20 box to change a relay. and when the relay didn't fix the problem; we had to follow the wiring diagram. Everything was overwhelming. But all that been said; I still take a full responsibility for my action and I hope this will not repeat itself again. Thank you.


Synopsis: Technicians reported leaving a flashlight in the nose wheel well after maintenance; causing the nose landing gear to not retract; causing an Air Turn Back and precautionary landing.