Unexpected aircraft motion at gate after PIC sets parking brake. Flight crew vigilance required.

Attributes
ACN	306572
Time
Date	199506
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dsm
State Reference	IA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument pilot : atp
Experience	flight time last 90 days : 225 flight time total : 17000 flight time type : 250
ASRS Report	306572
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : commercial pilot : cfi pilot : atp pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 7000 flight time type : 200
ASRS Report	307331
Events
Anomaly	aircraft equipment problem : less severe non adherence other other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

After setting the parking brake at dsm and checking that the brakes were set by observing that the park brake light was on with normal hydraulic brake pressure and slight hand pressure to the top of the park brake handle, I ordered both engines shutdown. The first officer observed 'parking brake' on EICAS. Next, I turned the seat belt sign off, then continued my SOP. While I was going through my shutdown procedures the first officer yelled 'the airplane is moving.' we both immediately applied brakes with the aircraft stopping abruptly. There was no physical contact with the jetway or any ground equipment or ground personnel. So there was no aircraft damage and I do not believe there were any passenger injured. Supplemental information from acn 307331: when I looked up to get the checklist I noticed the airplane was moving. I then yelled out, 'the airplane is moving' and got on the brakes.

Original NASA ASRS Text

Title: UNEXPECTED ACFT MOTION AT GATE AFTER PIC SETS PARKING BRAKE. FLC VIGILANCE REQUIRED.

Narrative: AFTER SETTING THE PARKING BRAKE AT DSM AND CHKING THAT THE BRAKES WERE SET BY OBSERVING THAT THE PARK BRAKE LIGHT WAS ON WITH NORMAL HYD BRAKE PRESSURE AND SLIGHT HAND PRESSURE TO THE TOP OF THE PARK BRAKE HANDLE, I ORDERED BOTH ENGS SHUTDOWN. THE FO OBSERVED 'PARKING BRAKE' ON EICAS. NEXT, I TURNED THE SEAT BELT SIGN OFF, THEN CONTINUED MY SOP. WHILE I WAS GOING THROUGH MY SHUTDOWN PROCS THE FO YELLED 'THE AIRPLANE IS MOVING.' WE BOTH IMMEDIATELY APPLIED BRAKES WITH THE ACFT STOPPING ABRUPTLY. THERE WAS NO PHYSICAL CONTACT WITH THE JETWAY OR ANY GND EQUIP OR GND PERSONNEL. SO THERE WAS NO ACFT DAMAGE AND I DO NOT BELIEVE THERE WERE ANY PAX INJURED. SUPPLEMENTAL INFO FROM ACN 307331: WHEN I LOOKED UP TO GET THE CHKLIST I NOTICED THE AIRPLANE WAS MOVING. I THEN YELLED OUT, 'THE AIRPLANE IS MOVING' AND GOT ON THE BRAKES.

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.