A B737 after parking on a gate and receiving the 'chocks in' the captain released the parking brake....

Attributes
ACN	623425
Time
Date	200406
Day	Tue
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 200 flight time total : 8400 flight time type : 4000
ASRS Report	623425
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	non adherence : far non adherence : published procedure other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : regained aircraft control
Consequence	other other Other
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Company

Narrative:

Had just parked the aircraft at gate and were completing the parking checklist. The captain released the parking brake after receiving the 'chocks in' signal from the marshaller. While reading the checklist we noticed that the aircraft seemed to be moving backwards, but we both initially attributed this perception to the fact that the jetway was moving. I then checked the ground to my right and it became clear that we were, in fact, rolling backward. I immediately applied the brakes to stop the aircraft and the captain reset the parking brake. The lead flight attendant (and I believe several passenger) were knocked over by the stop, but no one reported being injured. The captain opened his window to find out what had happened and we think we heard a snippet of the conversation between a ramp agent and the ramp lead indicating that the agent only had 1 chock (and our bad luck, he apparently put it in front of the wheel), instead of at least two. It looked like the lead immediately realized the fault was theirs, as he went quickly to get the towbar since we were no longer positioned properly at the jetway. They towed the aircraft back into position and properly chocked it.

Original NASA ASRS Text

Title: A B737 AFTER PARKING ON A GATE AND RECEIVING THE 'CHOCKS IN' THE CAPT RELEASED THE PARKING BRAKE. ACFT ROLLED BACKWARDS. WHEN BRAKES WERE APPLIED CABIN ATTENDANT AND PAX WERE KNOCKED OVER. NO INJURIES.

Narrative: HAD JUST PARKED THE ACFT AT GATE AND WERE COMPLETING THE PARKING CHKLIST. THE CAPT RELEASED THE PARKING BRAKE AFTER RECEIVING THE 'CHOCKS IN' SIGNAL FROM THE MARSHALLER. WHILE READING THE CHKLIST WE NOTICED THAT THE ACFT SEEMED TO BE MOVING BACKWARDS, BUT WE BOTH INITIALLY ATTRIBUTED THIS PERCEPTION TO THE FACT THAT THE JETWAY WAS MOVING. I THEN CHKED THE GND TO MY R AND IT BECAME CLR THAT WE WERE, IN FACT, ROLLING BACKWARD. I IMMEDIATELY APPLIED THE BRAKES TO STOP THE ACFT AND THE CAPT RESET THE PARKING BRAKE. THE LEAD FLT ATTENDANT (AND I BELIEVE SEVERAL PAX) WERE KNOCKED OVER BY THE STOP, BUT NO ONE RPTED BEING INJURED. THE CAPT OPENED HIS WINDOW TO FIND OUT WHAT HAD HAPPENED AND WE THINK WE HEARD A SNIPPET OF THE CONVERSATION BTWN A RAMP AGENT AND THE RAMP LEAD INDICATING THAT THE AGENT ONLY HAD 1 CHOCK (AND OUR BAD LUCK, HE APPARENTLY PUT IT IN FRONT OF THE WHEEL), INSTEAD OF AT LEAST TWO. IT LOOKED LIKE THE LEAD IMMEDIATELY REALIZED THE FAULT WAS THEIRS, AS HE WENT QUICKLY TO GET THE TOWBAR SINCE WE WERE NO LONGER POSITIONED PROPERLY AT THE JETWAY. THEY TOWED THE ACFT BACK INTO POS AND PROPERLY CHOCKED IT.

Data retrieved from NASA's ASRS site as of July 2007 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.

A B737 after parking on a gate and receiving the 'chocks in' the captain released the parking brake. Aircraft rolled backwards. When brakes were applied cabin attendant and passenger were knocked over. No injuries.