Parking brake failed, aircraft rolled into ground power unit and destroyed it.

Attributes
ACN	275851
Time
Date	199406
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mco
State Reference	FL
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Jetstream 32
Operating Under FAR Part	Part 135
Flight Phase	ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 230 flight time total : 4200 flight time type : 230
ASRS Report	275851
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 279 flight time total : 2750 flight time type : 982
ASRS Report	275850
Events
Anomaly	conflict : ground critical other anomaly other anomaly other
Independent Detector	other flight crewa other other : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

We were marshalled to a point on the ramp about 3 ft from a ground power unit. The aircraft came to a complete stop using the toe brakes. I set the parking brake and announced to first officer þcool down (of engines) complete, parking brake is set,' our company calls required to initiate engine shutdown. The first officer pushed engine stop switches. Our company procedure requires monitoring of engine RPM gauges by both crew members with special crew actions at 50 percent RPM and 10 percent RPM. While we were watching engine gauges, we had a parking brake failure and the aircraft started to roll. We did not sense aircraft movement. As the left propeller was still winding down, it contacted the ground power unit. The ground power unit was destroyed, propellers bent, and pieces of ground power unit put 2 holes in aircraft skin. Factors contributing: 1) placement of ground power unit before aircraft is parked rather than after. 2) wheels were not chocked as soon as aircraft completely stopped with toe brakes. 3) company procedure required both crew to 'look inside' at exact time incident occurred. 4) small congested ramp area. 5) landing gear recently changed on aircraft. 6) parking brake locking mechanism discovered to be inoperative as discovered during investigation post incident. Supplemental information from acn 275850: the ground power unit was preparked in front of our left engine and was fairly close to the aircraft. The captain is also looking inside to place the engines on the start locks. At this time the parking brake failed and the aircraft rolled into the ground power unit.

Original NASA ASRS Text

Title: PARKING BRAKE FAILED, ACFT ROLLED INTO GND PWR UNIT AND DESTROYED IT.

Narrative: WE WERE MARSHALLED TO A POINT ON THE RAMP ABOUT 3 FT FROM A GND PWR UNIT. THE ACFT CAME TO A COMPLETE STOP USING THE TOE BRAKES. I SET THE PARKING BRAKE AND ANNOUNCED TO FO þCOOL DOWN (OF ENGS) COMPLETE, PARKING BRAKE IS SET,' OUR COMPANY CALLS REQUIRED TO INITIATE ENG SHUTDOWN. THE FO PUSHED ENG STOP SWITCHES. OUR COMPANY PROC REQUIRES MONITORING OF ENG RPM GAUGES BY BOTH CREW MEMBERS WITH SPECIAL CREW ACTIONS AT 50 PERCENT RPM AND 10 PERCENT RPM. WHILE WE WERE WATCHING ENG GAUGES, WE HAD A PARKING BRAKE FAILURE AND THE ACFT STARTED TO ROLL. WE DID NOT SENSE ACFT MOVEMENT. AS THE L PROP WAS STILL WINDING DOWN, IT CONTACTED THE GND PWR UNIT. THE GND PWR UNIT WAS DESTROYED, PROPS BENT, AND PIECES OF GND PWR UNIT PUT 2 HOLES IN ACFT SKIN. FACTORS CONTRIBUTING: 1) PLACEMENT OF GND PWR UNIT BEFORE ACFT IS PARKED RATHER THAN AFTER. 2) WHEELS WERE NOT CHOCKED AS SOON AS ACFT COMPLETELY STOPPED WITH TOE BRAKES. 3) COMPANY PROC REQUIRED BOTH CREW TO 'LOOK INSIDE' AT EXACT TIME INCIDENT OCCURRED. 4) SMALL CONGESTED RAMP AREA. 5) LNDG GEAR RECENTLY CHANGED ON ACFT. 6) PARKING BRAKE LOCKING MECHANISM DISCOVERED TO BE INOP AS DISCOVERED DURING INVESTIGATION POST INCIDENT. SUPPLEMENTAL INFO FROM ACN 275850: THE GND PWR UNIT WAS PREPARKED IN FRONT OF OUR L ENG AND WAS FAIRLY CLOSE TO THE ACFT. THE CAPT IS ALSO LOOKING INSIDE TO PLACE THE ENGS ON THE START LOCKS. AT THIS TIME THE PARKING BRAKE FAILED AND THE ACFT ROLLED INTO THE GND PWR UNIT.

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.