Mechanic called out to look at a forward cargo door for dents on B737-900 aircraft; used the length ...

Attributes
ACN	812857
Time
Date	200811
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
Qualification	technician : airframe technician : powerplant
Experience	maintenance technician : 6
ASRS Report	812857
Events
Anomaly	aircraft equipment problem : less severe maintenance problem : improper documentation non adherence : far non adherence : published procedure
Independent Detector	other other : 1
Resolutory Action	none taken : detected after the fact
Consequence	other
Factors
Maintenance	performance deficiency : logbook entry
Supplementary
Problem Areas	Maintenance Human Performance Aircraft
Primary Problem	Maintenance Human Performance

Narrative:

On aircraft X I was called out to look at a forward cargo door for dents. My measures were 1.1 inch by 2.5 inches by .040 inch deep. Per the srm; my width/depth must be 30 or more. I used the wrong measurement in my formula. (I used 2.5 inches/.040=62.5) my formula should have been 1.1 feet/.040-27. I placed the dent on maintenance history rather than deferred item reference srm allowable damage section. I have already closed the maintenance history and opened the correct deferred item in reference with srm allowable damage section. New general srm with maximum width versus classic minor axis. Just used the wrong measure. Callback conversation with reporter revealed the following information: reporter stated the next gen B737-700/800/900 structural repair manual (srm) uses the letter 'west'; meaning width; for the damage criteria formula west/Y; to determine if the aircraft damage requires immediate repair; or can be deferred under certain categories. The 'Y' factor represents the depth of the dent. Reporter stated the classic B737-300/400/500 srm's continue to use the letter 'a' for the width formula when determining their a/Y damage criteria. He just used the length measurement; instead of the width; for the damage calculations.

Original NASA ASRS Text

Title: MECHANIC CALLED OUT TO LOOK AT A FORWARD CARGO DOOR FOR DENTS ON B737-900 AIRCRAFT; USED THE LENGTH MEASUREMENT INSTEAD OF THE WIDTH MEASUREMENT; WHEN HE APPLIED THE W/Y FORMULA IN THE SRM FOR DETERMINING ALLOWABLE DAMAGE.

Narrative: ON ACFT X I WAS CALLED OUT TO LOOK AT A FORWARD CARGO DOOR FOR DENTS. MY MEASURES WERE 1.1 INCH BY 2.5 INCHES BY .040 INCH DEEP. PER THE SRM; MY WIDTH/DEPTH MUST BE 30 OR MORE. I USED THE WRONG MEASUREMENT IN MY FORMULA. (I USED 2.5 INCHES/.040=62.5) MY FORMULA SHOULD HAVE BEEN 1.1 FEET/.040-27. I PLACED THE DENT ON MAINT HISTORY RATHER THAN DEFERRED ITEM REF SRM ALLOWABLE DAMAGE SECTION. I HAVE ALREADY CLOSED THE MAINT HISTORY AND OPENED THE CORRECT DEFERRED ITEM IN REF WITH SRM ALLOWABLE DAMAGE SECTION. NEW GENERAL SRM WITH MAX WIDTH VERSUS CLASSIC MINOR AXIS. JUST USED THE WRONG MEASURE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE NEXT GEN B737-700/800/900 STRUCTURAL REPAIR MANUAL (SRM) USES THE LETTER 'W'; MEANING WIDTH; FOR THE DAMAGE CRITERIA FORMULA W/Y; TO DETERMINE IF THE AIRCRAFT DAMAGE REQUIRES IMMEDIATE REPAIR; OR CAN BE DEFERRED UNDER CERTAIN CATEGORIES. THE 'Y' FACTOR REPRESENTS THE DEPTH OF THE DENT. REPORTER STATED THE CLASSIC B737-300/400/500 SRM'S CONTINUE TO USE THE LETTER 'A' FOR THE WIDTH FORMULA WHEN DETERMINING THEIR A/Y DAMAGE CRITERIA. HE JUST USED THE LENGTH MEASUREMENT; INSTEAD OF THE WIDTH; FOR THE DAMAGE CALCULATIONS.

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.

Mechanic called out to look at a forward cargo door for dents on B737-900 aircraft; used the length measurement instead of the width measurement; when he applied the west/Y formula in the srm for determining allowable damage.