Narrative:

We arrived at the gate with the APU running; and shut down both engines. I was holding the foot brakes; but forgot to apply the parking brake. I thought we were chocked. I do not remember not getting the 'chocks in' signal. I released the foot brakes. We opened the cockpit door and I turned around as I was saying goodbye to the first officer as he started to get up to leave the cockpit.I did not feel any motion. I looked forward again and thought I saw the jet way moving. I soon realized it was an optical illusion; and that the airplane was actually rolling straight backwards. I quickly applied the foot brakes; and realized I had not set the parking brake. I subsequently applied the parking brake to keep the airplane from rolling anymore.since both engines were already shut down; the ramp crew tugged us back into position. The jet way attached to the airplane; and we deplaned without event. There were no injuries; and there was no damage to the aircraft or any ground equipment or injury to personnel. I estimate the distance we rolled was 5 feet or less.I allowed myself to be distracted and rushed; as we were in a hurry to get the airplane parked so both the first officer (first) and I (second) could leave the airplane and run to commuting flights home. I didn't pay close enough attention and assumed that the airplane was chocked. As I mentioned; I don't remember not getting the signal. In my distracted state; I forgot to apply the parking brake. With both engines shut down and a ramp that appeared level; I never imagined we would roll forward or backwards.in the case of this event; because both engines were shut down; the seatbelt sign was off; and the cockpit door was open; I let my guard down and did not closely monitor the situation to make sure the parking brake was set and the airplane was chocked.after this experience; I will be sure to always apply the parking brake as soon as we are stopped in the gate. I will not rely on holding the footbrakes; even (and especially) if both engines are shut down. This is a simple thing to prevent; and I have learned a sobering lesson; fortunately without damage to any equipment or injury to anyone.

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Original NASA ASRS Text

Title: Embraer ERJ-170 flight crew reported not setting the parking brake at the gate and the aircraft began to roll.

Narrative: We arrived at the gate with the APU running; and shut down both engines. I was holding the foot brakes; but forgot to apply the parking brake. I thought we were chocked. I do not remember not getting the 'chocks in' signal. I released the foot brakes. We opened the cockpit door and I turned around as I was saying goodbye to the First Officer as he started to get up to leave the cockpit.I did not feel any motion. I looked forward again and thought I saw the jet way moving. I soon realized it was an optical illusion; and that the airplane was actually rolling straight backwards. I quickly applied the foot brakes; and realized I had not set the parking brake. I subsequently applied the parking brake to keep the airplane from rolling anymore.Since both engines were already shut down; the ramp crew tugged us back into position. The jet way attached to the airplane; and we deplaned without event. There were no injuries; and there was no damage to the aircraft or any ground equipment or injury to personnel. I estimate the distance we rolled was 5 feet or less.I allowed myself to be distracted and rushed; as we were in a hurry to get the airplane parked so both the FO (first) and I (second) could leave the airplane and run to commuting flights home. I didn't pay close enough attention and assumed that the airplane was chocked. As I mentioned; I don't remember not getting the signal. In my distracted state; I forgot to apply the parking brake. With both engines shut down and a ramp that appeared level; I never imagined we would roll forward or backwards.In the case of this event; because both engines were shut down; the seatbelt sign was off; and the cockpit door was open; I let my guard down and did not closely monitor the situation to make sure the parking brake was set and the airplane was chocked.After this experience; I will be sure to always apply the parking brake as soon as we are stopped in the gate. I will not rely on holding the footbrakes; even (and especially) if both engines are shut down. This is a simple thing to prevent; and I have learned a sobering lesson; fortunately without damage to any equipment or injury to anyone.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.