Air carrier flight crew reported the aircraft rolled back a few feet after parking at the gate at ORD when the parking brake was apparently not properly set.
Synopsis
Air carrier flight crew reported the aircraft rolled back a few feet after parking at the gate at ORD when the parking brake was apparently not properly set.
Narrative
We arrived at the gate XX at ORD airport; while parking at the gate; the gate marshaller was extremely close to the airplane to a point I had to lift my body up to see his signal. Once the marshaller gave me a stop; I pulled parking brake and both First Officer (FO) and I saw the parking 'ON' light (but I think I released too quick or had my finger still holding onto the parking brake button; which caused the parking to release) then I proceeded to finished my shutdown flow. Then while we were doing the shutdown checklist; we noticed the plane started to roll back; so I put my feet on the parking brake and engaged the hand brake. From the ramper; we rolled back about 3 ft and we went off the line. Caused us to restart the engine and move the plane forward. No injuries; just an unexpected event.Day 0 XA:30accidentally put it needs a logbook entry; but it doesn't; no where allow me to update it. Just wanted to mention it Cause: Early starts caused fatigue; unnecessary distraction from marshaller with limited vision of hand signal to gate; did not cross check and verify hand brake fully engage.Suggestions: It was mine responsibility to cross check all actions in flight; I should've paid more attention to all actions and cross check even the smallest actions in flight; not just out of habit and flows. Even I pulled the parking brake I should always wait a few seconds and verify that it was completely engage.
Second reporter narrative
Upon arriving to gate XX in ORD; we saw a clear safety envelope and 3 ramp agents to bring us into the gate. The marshaller was a bit hard to see as he was standing relatively close to the line and the Captain commented that it was difficult to see the signals but we could see them and saw when we received the stop signal. At that time I saw the Captain grab the parking brake lever with his hand and (I thought) I saw the parking light illuminate; however; he then shutdown the engine and began his shutdown flow and I put the transponder in standby; then grabbed the shutdown checklist which was called for. I began reading it and perhaps halfway through we noticed the plane slowing moving. The Captain was immediately on the brakes then set the parking brake. The gate agent didn't want to attach the bridge as our wheel was now aft of the parking line; upon asking the ramp if they could tow us in; they said they were unable and we'd have to start an engine. The Captain did his before start flow and called the flight attendants (FAs) to verify everyone was seated; and the ramp gave us clear to start and the Captain started the engine and we were marshalled 3 feet to park. After the event we then shutdown normally.Cause: A small distraction led the Captain to mistakenly disengage the parking brake lever; the First Officer (FO) (myself) should have double checked the status of the parking brake before grabbing the checklist; and should have been eyes outside until beginning to read the checklist.Suggestions: Although it is not specifically listed that the FO should verify with their own eyes the items on the Captains flows and responsibilities; I do believe that a good crew checks each other to make sure nothing was missed. The shutdown checklist is a 'challenge and respond' so it implies the challenger should solely read; a quick glance could have prevented this. Additionally the Captain should not look back inside until the chocks inserted sign is given by ramp.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.