After changing the left wing scan illumination light; mechanic tries to avoid the gate air duct whil...

Attributes
ACN	807341
Time
Date	200810
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
Qualification	technician : powerplant technician : airframe
ASRS Report	807341
Events
Anomaly	maintenance problem : improper maintenance non adherence : far non adherence : published procedure
Independent Detector	other other : 1
Resolutory Action	none taken : detected after the fact
Consequence	other other
Factors
Maintenance	performance deficiency : non compliance with legal requirements
Supplementary
Problem Areas	Maintenance Human Performance
Primary Problem	Maintenance Human Performance

Narrative:

The l-hand wing scan light was found to be not working. Being under the assumption that our manlift was still tagged out; I obtained a belt loader from the next gate to change the light. I carefully approached the side of the fuselage; raised the hand RAIL; and changed the light. During this time the gate air conditioning duct had been turned on (when this is turned on it expands and has a tendency to also extend). I lowered the hand RAIL and restarted the belt loader to back it up. Being aware of the aircraft duct; I cut the wheel to avoid crushing it. I proceeded to back up and had turned the wheel too much because I grazed the #1 engine inlet cowl at the 7 O'clock position. The damage was measured at 9 inches long; 4 inches wide; and .325 inches deep. I immediately informed my lead and supervisor of the event. At that time I found out that the manlift had been fixed the day before. I realize that I should have checked with my supervisor as to the state of the manlift before proceeding. My assumption and greater concern for gate air led to aircraft damage.

Original NASA ASRS Text

Title: AFTER CHANGING THE LEFT WING SCAN ILLUMINATION LIGHT; MECHANIC TRIES TO AVOID THE GATE AIR DUCT WHILE BACKING THE BELT LOADER; BUT GRAZES #1 ENG INLET COWL; CAUSING A NINE INCH LONG; FOUR INCH WIDE AND .325 INCH DEEP GOUGING OF INLET SKIN ON A B737.

Narrative: THE L-HAND WING SCAN LIGHT WAS FOUND TO BE NOT WORKING. BEING UNDER THE ASSUMPTION THAT OUR MANLIFT WAS STILL TAGGED OUT; I OBTAINED A BELT LOADER FROM THE NEXT GATE TO CHANGE THE LIGHT. I CAREFULLY APCHED THE SIDE OF THE FUSELAGE; RAISED THE HAND RAIL; AND CHANGED THE LIGHT. DURING THIS TIME THE GATE AIR CONDITIONING DUCT HAD BEEN TURNED ON (WHEN THIS IS TURNED ON IT EXPANDS AND HAS A TENDENCY TO ALSO EXTEND). I LOWERED THE HAND RAIL AND RESTARTED THE BELT LOADER TO BACK IT UP. BEING AWARE OF THE ACFT DUCT; I CUT THE WHEEL TO AVOID CRUSHING IT. I PROCEEDED TO BACK UP AND HAD TURNED THE WHEEL TOO MUCH BECAUSE I GRAZED THE #1 ENG INLET COWL AT THE 7 O'CLOCK POS. THE DAMAGE WAS MEASURED AT 9 INCHES LONG; 4 INCHES WIDE; AND .325 INCHES DEEP. I IMMEDIATELY INFORMED MY LEAD AND SUPVR OF THE EVENT. AT THAT TIME I FOUND OUT THAT THE MANLIFT HAD BEEN FIXED THE DAY BEFORE. I REALIZE THAT I SHOULD HAVE CHKED WITH MY SUPVR AS TO THE STATE OF THE MANLIFT BEFORE PROCEEDING. MY ASSUMPTION AND GREATER CONCERN FOR GATE AIR LED TO ACFT DAMAGE.

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.

After changing the left wing scan illumination light; mechanic tries to avoid the gate air duct while backing the belt loader; but grazes #1 engine inlet cowl; causing a nine inch long; four inch wide and .325 inch deep gouging of inlet skin on a B737.