A line mechanic reports the APU and #2 engine fire bottles were inadvertently discharged; even with ...

Narrative:

At shift change; [I] received a gate call for a B737 aircraft with numerous items to be addressed. Last item; due to wheel well fault; had to change fire control unit (FCU). Called for paper work; pulled FCU; verified proper part number (P/north) to stores. Part arrived before paperwork arrived. And being pressed for time; had pulled circuit breaker prior to removal; and thought powering down aircraft would negate any electrical power to FCU. Swapped out FCU's and preformed operations check; operations good; then discovered light plate was missing. [I] powered down aircraft battery switch to 'off'. While installing light plate had to slightly move APU and #2 engine fire handles for installation of light plate. [I] verified discharge [of fire bottles]. Pilot refused to take aircraft or have an MEL issued for [crew] oxygen (O2) at 1;000 psi for jump seat riders standing by. [I] serviced O2 to full level. Finished all other maintenance items except FCU; and were at least 30-minute into [departure] delay. Aircraft temporarily taken out of service; and all involved sent for drug and alcohol [tests]. Suggest [that] regardless of delay; wait for paperwork to arrive to start job.

Original NASA ASRS Text

Title: A Line Mechanic reports the APU and #2 engine fire bottles were inadvertently discharged; even with the battery switch 'OFF'; when he was transferring a lighted faceplate from a malfunctioning Fire Control Panel (FCP) to a replacement FCP on the P-8 Center Control console of a B737 aircraft.

Narrative: At shift change; [I] received a gate call for a B737 aircraft with numerous items to be addressed. Last item; due to wheel well fault; had to change Fire Control Unit (FCU). Called for paper work; pulled FCU; verified proper Part Number (P/N) to Stores. Part arrived before paperwork arrived. And being pressed for time; had pulled circuit breaker prior to removal; and thought powering down aircraft would negate any electrical power to FCU. Swapped out FCU's and preformed operations check; operations good; then discovered light plate was missing. [I] powered down aircraft battery switch to 'OFF'. While installing light plate had to slightly move APU and #2 engine fire handles for installation of light plate. [I] verified discharge [of fire bottles]. Pilot refused to take aircraft or have an MEL issued for [crew] oxygen (O2) at 1;000 PSI for jump seat riders standing by. [I] serviced O2 to full level. Finished all other maintenance items except FCU; and were at least 30-minute into [departure] delay. Aircraft temporarily taken out of service; and all involved sent for drug and alcohol [tests]. Suggest [that] regardless of delay; wait for paperwork to arrive to start job.

Data retrieved from NASA's ASRS site as of July 2013 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	993461
Time
Date	201202
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Dusk
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Fire Protection System
Person 1
Function	Technician
Qualification	Maintenance Powerplant Maintenance Airframe
Experience	Maintenance Technician 25
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

A line mechanic reports the APU and #2 engine fire bottles were inadvertently discharged; even with the battery switch 'off'; when he was transferring a lighted faceplate from a malfunctioning fire control panel (fcp) to a replacement fcp on the P-8 center control console of a B737 aircraft.