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During preflight a B737 crew turned the 'B' hydraulic pumps off and 'a' hydraulic pumps on due to wind conditions. During engine start the tow bar broke when the 'a' system pressurized.
| Attributes | |
| ACN | 815086 |
| Time | |
| Date | 200812 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | agl single value : 0 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : sct.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-500 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : pushback |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 208 |
| ASRS Report | 815086 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 245 |
| ASRS Report | 815088 |
| Events | |
| Anomaly | non adherence : company policies non adherence : published procedure non adherence : far |
| Independent Detector | aircraft equipment other aircraft equipment : hydraulic pressure other flight crewa other flight crewb |
| Resolutory Action | none taken : detected after the fact |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Weather |
| Primary Problem | Flight Crew Human Performance |
Narrative:
Windy conditions led to an electric hydraulic pump being turned on prior to prepping the airplane for the next leg. The 'a' electric pump was turned on. During the captain's flow; I accidentally turned off the 'B' pump while leaving both 'a' pumps on. This resulted in an 'a' on and 'B' off condition. During the before start checklist; both the first officer and I saw 2 pumps on and 2 pumps off. We failed to xchk the hydraulic pressure gauge or the switch labels. When the aircraft was being pushed back; the towbar broke. There was no other damage and no one was injured. Verify correct switch position and xchk the pressure gauge. Don't rush the checklist.
Original NASA ASRS Text
Title: DURING PREFLIGHT A B737 CREW TURNED THE 'B' HYDRAULIC PUMPS OFF AND 'A' HYDRAULIC PUMPS ON DUE TO WIND CONDITIONS. DURING ENGINE START THE TOW BAR BROKE WHEN THE 'A' SYSTEM PRESSURIZED.
Narrative: WINDY CONDITIONS LED TO AN ELECTRIC HYD PUMP BEING TURNED ON PRIOR TO PREPPING THE AIRPLANE FOR THE NEXT LEG. THE 'A' ELECTRIC PUMP WAS TURNED ON. DURING THE CAPT'S FLOW; I ACCIDENTALLY TURNED OFF THE 'B' PUMP WHILE LEAVING BOTH 'A' PUMPS ON. THIS RESULTED IN AN 'A' ON AND 'B' OFF CONDITION. DURING THE BEFORE START CHKLIST; BOTH THE FO AND I SAW 2 PUMPS ON AND 2 PUMPS OFF. WE FAILED TO XCHK THE HYD PRESSURE GAUGE OR THE SWITCH LABELS. WHEN THE ACFT WAS BEING PUSHED BACK; THE TOWBAR BROKE. THERE WAS NO OTHER DAMAGE AND NO ONE WAS INJURED. VERIFY CORRECT SWITCH POS AND XCHK THE PRESSURE GAUGE. DON'T RUSH THE CHKLIST.
Data retrieved from NASA's ASRS site as of May 2009 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.