Date: 201407
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Weather elements / visibility: Thunderstorm
Light: Daylight
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight phase: Parked
Aircraft component: Filter
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Weather; Procedure; Manuals; Human Factors; Aircraft
Primary problem: Procedure

Narrative: I; Mechanic X; was advised that a B777 had a ground interrupt the previous day; during a pushback engine start for a Thrust Reverser (T/R) Isolation [EICAS] message.  I was assigned a maintenance write-up for a Hydraulic Fluid High Particle Count item on the B777. I was informed the job was started by previous shift; and the Left and Right Hydraulic Systems were depressurized and drained. [We were] also rushed; in a sense that the  aircraft was [scheduled] for a flight. I was to work the aircraft outside on the hardstand. I did not feel it should be worked outside due to high winds and hurricane threat. I set up to perform job task and I accepted to work the Left Engine. I removed the first filter bowl and proceeded to get soaked with hydraulic fluid under pressure; which in turn filled my line tool box and the work lift. I called for help and a Lead Mechanic and another Aircraft maintenance Technician (AMT) came over to help. It was then that the Lead Mechanic informed Management that the aircraft required hangar space. I had to clean up my body and tools of hydraulic fluid before continuing the task. I completed the filter replacement; safetied them and stowed [Lockout] pins in pouch and then broke for lunch. After returning from lunch; the aircraft hydraulic reservoirs were being serviced and completed. Another Lead Mechanic who was working the aircraft informed me he was going to the flight deck to restore all [Circuit] Breakers (C/Bs) and pressurize [the Hydraulic Systems] and I was to leak check my side; all filters checked good. At this point; myself and another AMT working the aircraft went to sign-off the write-up item because again; they were rushing to get the aircraft to the gate. I signed-off the Non-Routine item which stated the deactivation of the Thrust Reverser was reactivated; but I failed to read what was entailed in this task; entrusting [that] all Circuit Breakers were restored from what I was told; without physically checking myself. It was brought to my attention [that] you can only get this [EICAS] message upon aircraft engine start up. But further information given to me is that two AMTs had taxied this aircraft from the hangar to the gate and should have seen this [EICAS message] and if so; this ground interrupt would have never happened. I feel human factors played a serious roll in my actions and failure in this task.

Callback: Reporter stated he was one of four mechanics assigned to replace three hydraulic filters in each engine pylon. Dayshift had started the job card by depressurizing the Hydraulic Systems. He was working in the Left Engine Pylon Sailboat area; where the Left Hydraulic System Reservoir is located; as the wind began blowing. They were in compliance with the Aircraft Maintenance Manual (AMM) procedures. As he started to remove the first filter; he was immediately sprayed with Skydrol hydraulic fluid. He believes that movement of the rudder by the wind caused just enough residual hydraulic pressure to rebuild in the Left Hydraulic System. There was also thunderstorms and lightning in the area.Reporter stated that a Sub-Task in the AMM Hydraulic Filter change procedures to re-activate the collared Circuit Breakers (C/Bs) for the Thrust Reverser Isolation Valves in the lower E/E Bay compartment was missed; resulting in the ground interrupt and the B777 returned to the gate.

Second narrative: Afternoon; start of my shift. I; Mechanic Y; was assigned to work a B777 aircraft. The aircraft required hydraulic filter changes for the Engine Driven Pump (EDP) Filter Module; the AC Electric Motor Pump (ACMP) Filter Module and the System Return Filter Module for the Right Hydraulic System and the Left Hydraulic System. The aircraft was located at ZZZ Hangar; outside on Hardstand-1. I was given packages of ten filters and numerous seals and Illustrated Parts Catalog (IPC) material as well as seals for Aircraft on Ground (AOGs) status; also I was informed that the Hydraulic Reservoirs were drained. I commenced working on the Right-Hand (R/H) Hydraulic System from a powered mobile lift [Stand]. During the course [of work]; weather at the time was sunny and windy. It then became gusting with significant strength; I had to use my tools to hold down paperwork/parts and at times the parts were blowing off the stand; even if they were weighted down. Keep in mind that I was made aware this aircraft was on a flight that night.As the day progressed; the Mechanic working the Left Hydraulic System; yelled out. He got sprayed with SKYDROL hydraulic fluid on his face and on his coveralls. I had to take him into hangar so he could get some treatment for face area and cleaned up. The winds were affecting and hampering us [so] the Lead Mechanic went in to the hangar and informed Management that this aircraft needed to be brought into the hangar. The Lead Mechanic returned [and said] that we going to put the aircraft in the Hangar Bay. I returned to the aircraft; applying absorb-all [material] to work stand. I then moved the ground equipment away from the aircraft; so we can move the aircraft to the hangar. Now; I had to relocate all the equipment; tools and material into the Hangar Bay. I continued working on changing filters for Right Hydraulic System. Aircraft in the Hangar Bay; I returned and worked replacing the filters and completed safetying; so that the aircraft can be re-serviced with hydraulic fluid for both hydraulic systems. At that time; Mechanic X was still working on the Left Hydraulic System; I took a short break to clean the SKYDROL fluid off of my arms and neck area and treated my arms. I returned back to the Hangar Bay and mechanics were re-servicing the hydraulic reservoirs. Soon after; they pressurized the Right ACMP Hydraulic Pump and purged the air out of the system by operating the flight controls. As that was occurring; I moved the ground equipment away from the Right Engine pylon so they can motor the Right Engine and I can perform a Leak Check of the Right ACMP Filter Module; Return Filter Module; and Engine Driven Pump (EDP) Filter Modules. With this all completed; I checked the area in the pylon and closed the outboard Right Eng Pylon Doors; then I moved to inboard side of Right Eng pylon (Note: Pylon Placard on inside of door) where I reactivated the Thrust Reverser (T/R) by removing the two Lockout pins and placing then in the stowage bags; then closing pylon doors securing them close. I moved all the mobile stands away from the area where I was working by the Right Engine; so the aircraft can be push out of the hangar and be taken to the gate. I returned to the Maintenance Office to sign-off the original item for the filter replacement and there was a Maintenance write-up item for the deactivation of the Right Engine Thrust Reverser (T/R). I signed-off the Right Engine reactivation. The aircraft was push out the hangar to go to the gate. I was made aware some time the next day that aircraft had a ground interrupt and returned to the gate; and that they found T/R Circuit Breakers (C/Bs) pulled in the lower E/E Bay which caused an EICAS message displayed for the reversers. This event is concerning and I see that no one had the realization to the amount of time required in doing this job or the events that occurred. That this aircraft should not have been placed on a committed flight with the amount of time that was remaining; or even to have the work re-planned to a later date. With the necessary work that had to be done; the aircraft could or should have been staged in a location that was appropriate in doing this type of work (Hangar) for that particular weather inbound; as well having ample manpower to support.These T/R Circuit Breakers resulted in this ground interrupt. It would be ideal that any time a Circuit Breaker is pulled in a location that is remote; such as in lower E/E Bay; that; those breakers need to be written-up; so as to assure it receives special attention; especially at Shift/Crew change. Having long red streamers attached at the open hatches; hanging down as a visual indication that work is in progress in that particular compartment. I am seriously bothered by this and I will take self solution to this matter. High workload. Time pressure. Push off gate and after engine start.


Synopsis: Two aircraft maintenance technicians (AMTs) report a B777 aircraft returned to a departure gate after a Thrust Reverser (T/R) Isolation message had appeared. Two T/R Isolation Valve Circuit Breakers (C/Bs) in the lower E/E Bay had not been reactivated after replacement of Left and Right Hydraulic System filters. Technician was also sprayed with Skydrol hydraulic fluid.