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Aircraft hydraulic system 'a' became inadvertently pressurized during tow bar disconnect following pushback. Tow bar broken by hydraulic pressure. No injuries.
| Attributes | |
| ACN | 117469 |
| Time | |
| Date | 198907 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : iad |
| State Reference | VA |
| 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 | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | ground : preflight other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : cfi pilot : flight engineer |
| Experience | flight time last 90 days : 200 flight time total : 7000 flight time type : 200 |
| ASRS Report | 117469 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | other flight crewa other other : unspecified |
| Resolutory Action | none taken : insufficient time |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
Aircraft was an medium large transport. APU deferred inoperative. Scheduled flight from iad-sav. Started #1 engine at gate with ground electrics and pneumatics. #1 generator placed on line and aircraft pushed back. Brakes are set and mechanic attempts to remove tow bar from nose gear. At that moment the #1 generator quits. Unknown to us, the battery was dead and we lost all electrical power (company just recently removed procedure for checking battery during short stopovers). With the #1 engine running and no electrical power, the 'a' hydraulic system pressurized. With the tow bar still connected, and unable to talk to anyone, the tow bar to aircraft linkage snapped. Later we checked into how long the APU had been deferred inoperative. Our 'beef' is that such an important piece of aircraft equipment should not be allowed to be deferred for days at a time. If our APU had been repaired at an earlier maintenance opportunity, this never would have happened.
Original NASA ASRS Text
Title: ACFT HYDRAULIC SYSTEM 'A' BECAME INADVERTENTLY PRESSURIZED DURING TOW BAR DISCONNECT FOLLOWING PUSHBACK. TOW BAR BROKEN BY HYDRAULIC PRESSURE. NO INJURIES.
Narrative: ACFT WAS AN MLG. APU DEFERRED INOP. SCHEDULED FLT FROM IAD-SAV. STARTED #1 ENGINE AT GATE WITH GND ELECTRICS AND PNEUMATICS. #1 GENERATOR PLACED ON LINE AND ACFT PUSHED BACK. BRAKES ARE SET AND MECHANIC ATTEMPTS TO REMOVE TOW BAR FROM NOSE GEAR. AT THAT MOMENT THE #1 GENERATOR QUITS. UNKNOWN TO US, THE BATTERY WAS DEAD AND WE LOST ALL ELECTRICAL POWER (COMPANY JUST RECENTLY REMOVED PROC FOR CHECKING BATTERY DURING SHORT STOPOVERS). WITH THE #1 ENGINE RUNNING AND NO ELECTRICAL POWER, THE 'A' HYDRAULIC SYSTEM PRESSURIZED. WITH THE TOW BAR STILL CONNECTED, AND UNABLE TO TALK TO ANYONE, THE TOW BAR TO ACFT LINKAGE SNAPPED. LATER WE CHECKED INTO HOW LONG THE APU HAD BEEN DEFERRED INOP. OUR 'BEEF' IS THAT SUCH AN IMPORTANT PIECE OF ACFT EQUIPMENT SHOULD NOT BE ALLOWED TO BE DEFERRED FOR DAYS AT A TIME. IF OUR APU HAD BEEN REPAIRED AT AN EARLIER MAINT OPPORTUNITY, THIS NEVER WOULD HAVE HAPPENED.
Data retrieved from NASA's ASRS site as of August 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.