Date: 201908
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
ATC / advisory: Ramp ZZZ
Aircraft component: DC Battery
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Workload; Troubleshooting; Time Pressure; Communication Breakdown
Second reporter function: Captain; Relief Pilot
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance; Flight Deck / Cabin / Aircraft Event Illness / Injury
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; General Physical Injury / Incapacitation; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Company Policy; Human Factors; Procedure
Primary problem: Human Factors

Narrative: Pushed off Gate X. Taxiing out; we had gotten a WARN ELEX status message. Contacted Maintenance and asked Ground Control for an area where we could stop to work with the maintenance issue at hand. We were on Taxiway W short of S. Maintenance instructed us to go to the maintenance page and pull up ATA code 31 and push the Clear/Delete and erase the status message. The message was latched and would not clear. Maintenance had informed us that the battery had been changed in the aircraft and the system was asking for a system test that it was not able to perform. We were then told to return to the gate because they needed to reset the system and that we could not depart with the system in this condition. The Captain made a PA informing the passengers that we were having to return to the gate for a maintenance issue. The [Relief Pilot] spoke to the Purser informing him of the maintenance issue we were having and to let the rest of the flight attendants know we were returning to the gate for maintenance to clear the problem. We taxied S; Y; and held short of U as Ramp was going to park us in the ball park to meet Maintenance. Because of a 737 that was in the way; they instead sent us to [Gate] Y. At [Gate] Y awaited for Ramp to park us. We were a surprise to the ramp personnel because it didn't seem like they were informed that we were coming in. After parking; the Captain instructed the flight attendants to disarm the doors because Maintenance would be coming on.  Maintenance showed up shortly after. A mechanic got on the ground call and the Captain talked to him through the inter phone. We tried to clear the message again and again it did not work. The mechanic on the inter phone told us they would need to come up. A short time later I heard a male scream from the back (as it turns out it was our flight attendant who had fallen through the open access hatch) and another mechanic was in the hatch area under the floor. At no time were we forewarned that a mechanic would enter through the floor Electronics and Equipment access hatch so that we could relay that to the flight attendants to remain clear of the hatch area and keep our passengers away. Again; we confirmed that the doors were disarmed thinking that they would enter through the forward entry door and waited for the jetway to move before the incident happened. After the incident; the Captain had me call Operations. I called Operations and informed them of what had happened and requested paramedics and a Flight Attendant Supervisor to come to the aircraft. The paramedics showed up as did Port Authority Police. The Port Authority Police were in the flight deck entry area talking to the Captain and asking for his info and why there was no Supervisor present. I called Operations a few more times requesting a Flight Attendant Supervisor and or any Supervisor. I informed Operations that the Port Authority [Police] required a Supervisor be there for this type of event. I was informed that the flight attendant and mechanic were both transported to the hospital to get checked. I remained in the flight deck throughout the incident relaying information to Operations and monitoring the radios and performing duties I was given.


Second narrative: Pushed back on time from Gate X. Soon thereafter; we got a 'WARN ELEX' status message. We made a request with ZZZ Ground Control to stop the aircraft to troubleshoot the problem with Maintenance. We were instructed to stop at Taxiway W holding short of Taxiway S. Maintenance told us to go to the maintenance page code 31 to click erase to clear the status message unsuccessfully. Then we were instructed to select clear/ delete several times. This was also unsuccessful. Maintenance informed us that this aircraft just had the battery changed and the system was requesting a test. Maintenance asked us to contact Ramp to taxi to the ball park; but due to a B-737 obstructing the access; we were instructed to return to Gate Y. PA was made by me to the passengers explaining the situation. The Purser and flight attendants were also notified. We performed the after landing flow while taxiing to Gate Y. Ramp personnel were kind of surprised to see an aircraft approaching Gate Y. It looks like they were not expecting us. After being marshaled into Gate Y; parking brake was set; engines shutdown and parking checklist completed; Maintenance and flight crew attempted to clear the status message several times via intercom without success. Maintenance indicated the need to come onboard. I immediately called the Purser and ordered to disarm the doors because Maintenance needed to come onboard. All of the sudden; we heard a male loud scream. When I turned around; I saw the Electronics and Equipment compartment hatch opened a mechanic trying to come up and the Purser's right leg all the way into the hole up to his waist resulting in body injuries. I came out of my seat to help him out and notice a cut on his right elbow. I asked him if he wanted to be replaced he said yes; but I also wanted to have him checked by medical personal since he looked in shock and in pain. I immediately requested a Flight Attendants Supervisor and the paramedics to come onboard. We also requested a Flight Attendant replacement. Several PA announcements were made by me to keep the passengers informed. We were never warned by Maintenance via intercom that Maintenance would come up to the aircraft via the Electronics and Equipment compartment so we could have coordinated with the flight attendance to stay clear of the hatch to prevent a fall. We suggested to reboot the aircraft to reset the message. After a reboot and a couple procedures performed; Maintenance finally managed to clear and reset the message. At the same time I called my Dispatcher to add more gas to fly faster; re-release the flight plan and to make sure our flight plan was still active. Port Authority Police interrogated me and took my driver license number. There was no Supervisor on site for a long while. Later I was informed that the Flight Attendants Supervisor had gone in the ambulance to the hospital with the injured Flight Attendant and the mechanic involved in the incident. I believe as a courtesy he/she could have stopped by the flight deck to introduce themselves and to say their intentions. After we had our replacement Flight Attendant; our new released 2 paper flight plan and MRD; our fuel was still not onboard. I had to personally get out of my seat open the jet bridge door and shout to the fueler to bring the total fuel to 87;500 pounds. Once we got our fuel; we were on our way to ZZZ1.


Synopsis: First Officer reported WARN ELEXEICAS Message on taxi; requiring resets and Maintenance to meet aircraft at remote without boarding stairs. Flight Attendant fell through the access panel to the Forward Avionics bay; landing on a mechanic; injuring them both.