ERJ-170 flight crew reported an inadvertant aircraft rollback from the departure gate during engine start due to flight crew's failure to properly configure the aircraft. The Captain quickly applied parking brakes to stop the rollback.
Synopsis
ERJ-170 flight crew reported an inadvertant aircraft rollback from the departure gate during engine start due to flight crew's failure to properly configure the aircraft. The Captain quickly applied parking brakes to stop the rollback.
Narrative
Aircraft X experienced unexpected aircraft movement/roll back. ZZZ airport gate is a power out gate. The crew was briefed by ground personnel and the Captain decided to have chalks removed before brake release. The ground personnel advised the Captain that the ramp area was not level. Hand signals were briefed between crew and the ground personnel. The jet bridge was moved clear of the aircraft. The Captain signaled for chalk removal and brake release. The brakes were released by the Captain. The hydraulic switches remained in the auto position. The aircraft had no control with toe brakes due to the lack of hydraulic pressure. The aircraft started rolling backward. Ground personnel signaled crossed X to stop the aircraft and flight crew noticed the roll back simultaneously. The Captain set the parking brake and the aircraft came to a stop abruptly. The Flight Attendant was standing at the time and hit their arm on the closet. No other injuries were reported to the crew. The flight crew discussed the event and decided to continue the flight as normal. No further delay was expected or occurred.
Second reporter narrative
Aircraft rolled back during engine start when it wasn't supposed to and an emergency brake was applied. The forward Flight Attendant (FA) lost balance and hit their forearm. I asked them if they were ok; they said yes; but they might have a bruise. Flight continued normally after. Before departing the gate at ZZZ; ground personnel advised no headset start and power out operation. We went over chalks out and engine start hand signals and I was asked whether I wanted to start first then chalks out or vice versa. I said chalks out then start. Was advised there is a slope on the ramp; this should have alerted me about something unusual but I didn't put it together. After giving the chalks out sign I noticed the aircraft rolling back. I was on the brakes but I had forgotten to put the electric hydraulic pump on for brakes to work. Applied the emergency brake.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.