Date: 201303
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
ATC / advisory: Ramp ZZZ
Aircraft component: Hydraulic System Pump
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Human factors: Situational Awareness; Communication Breakdown
Second reporter function: Flight Attendant (On Duty)
Anomaly: Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Ground Personnel
When detected: Aircraft In Service At Gate
Result: Flight Crew Returned To Gate; General Maintenance Action; General Evacuated
Contributing factors: Human Factors; Procedure; Aircraft
Primary problem: Aircraft

Narrative: During the walk around I noticed a light brown liquid dripping from the tail cone area of the fuselage and down the left side of the aircraft. Maintenance was called and reported that it was glycol. Upon taxi out we received an EICAS 'L HYD ELEC PUMP' advisory message so we returned to the gate. After making the arrival PA we shutdown and ran the parking checklist. We then noticed an overheat light illuminated for the L HYD ELEC PUMP; which was off. A Mechanic then came onboard and advised us we had smoke coming out of our left wing. The Captain directed me to call ARFF. I requested ARFF on Ramp Control frequency and was advised to request ARFF on operations frequency. While I was on the radio the Captain was making his PA and coordinating with the flight attendants. When we exited the aircraft I looked at the wing and noticed the left aft slide deployed and people sliding down it.


Second narrative: After departure; flight returned to the gate as the Captain announced that there was hydraulic problem. When we got to the gate; we started an orange juice and water beverage service. The FA1 made an announcement directing all passengers to collect all their belongings and get off of the aircraft. Shortly thereafter; FA1 made a subsequent announcement stating this is an emergency; get off the aircraft now; don't bring anything with you; this is an emergency. I was towards the rear of the aircraft serving the beverages when I heard the first announcement; so I went to the aft galley immediately. It seemed like only moments later the second announcement was made. I began looking in the cabin to see if I could determine what was happening. I could smell a strong odor that suggested something was burning. The passengers immediately began lining up and moving towards the rear of the cabin with urgency and were quickly amassed at the aft galley. I heard excited utterances from passengers but cannot recall the specific statements. Then a female passenger stated: 'she told us we had to use this exit.' I assessed the situation and with the limited facts I had; I determined that an emergency did indeed exist due to the announcements; the passenger stating she was directed to my exit; and passengers were indeed at my exit apparently following crew member commands. I determined that passengers would not have taken these actions without being directed to do so. I believed the only safe course of action was to follow procedures; arm the door; release the slide and begin evacuating the aircraft.


Synopsis: B757 flight crew and two of the flight attendants describe the events leading up to a return to the gate and an evacuation that follows when smoke is detected coming from the wheel well by ground personnel. The Captain had intended that passengers leave promptly through the 2L entry door; but some of the crew and passengers used the escape slide at the 4L door.