A line mechanic reports a tow lug on the nose landing gear of a B737-500 had broken during pushback....

Narrative:

I went out to aircraft remote ramp. While doing preflight checklist; turned on aircraft electric power and both hydraulic pumps to check for leaks. After completing checklist; I turned off both hydraulic pumps and waited on remote ramp. The tow crew showed up and I completed tow checklist; and turned on 'B' hydraulic pump for towing. While pushing back onto tango taxiway the tow shear pin broke; and we then returned to tango parking; at which point I discovered that 'a' hydraulic pump was 'on' and not the 'B' hydraulic pump. I was then notified by the ramp crew that the tow lug was broken and they could not move the aircraft any further; we were clear of taxiway tango; so I had them chock the aircraft there.

Original NASA ASRS Text

Title: A Line Mechanic reports a tow lug on the Nose Landing gear of a B737-500 had broken during pushback. Mechanic had turned the 'B' Electric Hydraulic pump 'Off'; instead of the 'A' Electric Hydraulic pump.

Narrative: I went out to aircraft remote Ramp. While doing Preflight Checklist; turned on aircraft electric power and both Hydraulic pumps to check for leaks. After completing Checklist; I turned off both Hydraulic pumps and waited on remote Ramp. The Tow Crew showed up and I completed Tow Checklist; and turned on 'B' Hydraulic pump for towing. while pushing back onto Tango Taxiway the Tow shear pin broke; and we then returned to Tango parking; at which point I discovered that 'A' Hydraulic pump was 'On' and not the 'B' Hydraulic pump. I was then notified by the Ramp Crew that the Tow lug was broken and they could not move the aircraft any further; we were clear of Taxiway Tango; so I had them chock the aircraft there.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	868279
Time
Date	200912
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Component
Aircraft Component	Nosewheel Steering
Person 1
Function	Technician
Qualification	Maintenance Powerplant Maintenance Airframe
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

A line mechanic reports a tow lug on the nose landing gear of a B737-500 had broken during pushback. Mechanic had turned the 'B' electric hydraulic pump 'off'; instead of the 'a' electric hydraulic pump.