Date: 201901
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: Exterior Pax/Crew Door
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Training / Qualification; Confusion
Second reporter function: Captain; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Detector: Person Flight Attendant; Person Flight Crew
When detected: Taxi
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: We were on a normal turn out of ZZZ when we had a slide deploy at the front of the airplane on the First Officer's side.The flight was progressing as normal. I had my MFD on the status page before push and all doors showed green. We did before start flows and before start checklist. We were cleared to push and also to cleared to start engines shortly thereafter. I reached over and started engine one. The number one engine was fully online and had stabilized when we received a master caution. The EICAS message was saying that the front door on the FO (First Officer) side was ajar. By this time we had completed the push and the ground crew was working on getting the airplane ready for taxi. The Captain called back to the flight attendants to check on the door and maybe try to recycle it. We sat there as we heard the Flight Attendant try to get the door shut. After a few seconds of messing with the door; I heard a loud hiss and the airplane started shaking. At that point we had determined that the slide had been deployed. The Flight Attendant then called to let us know what had happened. He tried opening the door and then closing it again. This was an honest mistake and had no malicious intent. It was an abnormal situation in a high pressure environment.The cause could've been a quick misinterpretation of wording between the crew. The FA (Flight Attendant) was told to recycle the door and I've heard that wording can be misinterpreted throughout the whole [company] fleet.Change the wording in the in-flight manual for the words 'recycling doors.' I've heard it can mean something different in all the airplanes and I guess maybe it was taken one way or [another] the night of the incident.


Second narrative: After push back in ZZZ on Aircraft X; we had an accidental slide deployment. Prior to push back; I verified the doors were green and told the ramp crew we were cleared to push. As we started the number 1 engine; once it came online we received a 'DOOR SERVICE FWD OPEN' warning message. I called back to the flight attendants and the number one answered. I had interrupted the safety demo that he was already doing. There must have been a perceived miscommunication as the next thing I knew there was a slide deployment. Thankfully no one was hurt when this honest mistake occurred and there was no willful intent by any crew member to deploy the slide.I believe the cause was miscommunication on the interphone between the CA (Captain) and the number one FA (Flight Attendant.) A contributing factor was the delayed flight and a rushed turn at the outstation.In the future I intend to treat any door issue similar to this event with a better initial reaction. First words to the FA will be to ensure the door is disarmed while following procedures more specifically.


Synopsis: ERJ-175 flight crew reported an inadvertent emergency slide deployment after pushback.