Narrative:

On walkaround, the flight crew reported a small dent in the #2 engine nose cowl. Dimensions were 1.5 inches diameter, 3/32 inches deep, beyond the limits of the structural repair manual (srm). I directed the mechanic to rework the dent to meet the limits of the srm which he did. There is a discrepancy in the srm where air traffic area chapter 54 says to rework dents to srm limits and chapter 51 air traffic area says dents can be reworked of metal .063 or less. Metal on the nose cowl is .100. The srm does not say you cannot rework dents of that thickness, but it does not say you can. The dent has been reworked and is within limits. The engineering department is going to clarify the manuals after conferring with boeing. Supplemental information from acn 506195: it was determined that the damage was out of limits per srm 54-10-01 page 104. The actual damage was 7 inches long X 1 1/2 inches wide X 3/32 inches deep. To conform to srm limits, the damage needed to have a factor of 30, meaning the depth was 1/13 of the minor width. We attempted to get an engineering variance authority/authorized to defer the damage, but we were unsuccessful. Commercial maintenance organization suggested to either lessen the depth of the damage by drilling a hole and using a slide hammer to pull the dent out, or increase the width of the damage and thus increase the factor and make allowable per srm 54-10-01 page 104. I opted to do the latter. In other words, I pounded the dent and made it wider. At that point the damage was within srm 54-10-01 limits, and the damage was deferred long term, and the cowl was to be replaced at 'C' check. The captain refused the aircraft, the flight consequently canceled. On mar/xa/01 I found out that the original damage was allowable (maintenance manual 51-00-99 page 201) up to 0.25 inches deep. But, we had reworked the area which was in violation of maintenance manual 51-70-01 page 1, paragraph 2C. The aircraft maintenance ferried (non revenue) to xyz for replacement of the nose cowl.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-300 WAS REPAIRED USING CONFLICTING AND CONFUSING SRM PROCS FOR NOW COWL DENT REWORK. PIC REFUSED ACFT FOR REVENUE FLT.

Narrative: ON WALKAROUND, THE FLC RPTED A SMALL DENT IN THE #2 ENG NOSE COWL. DIMENSIONS WERE 1.5 INCHES DIAMETER, 3/32 INCHES DEEP, BEYOND THE LIMITS OF THE STRUCTURAL REPAIR MANUAL (SRM). I DIRECTED THE MECH TO REWORK THE DENT TO MEET THE LIMITS OF THE SRM WHICH HE DID. THERE IS A DISCREPANCY IN THE SRM WHERE ATA CHAPTER 54 SAYS TO REWORK DENTS TO SRM LIMITS AND CHAPTER 51 ATA SAYS DENTS CAN BE REWORKED OF METAL .063 OR LESS. METAL ON THE NOSE COWL IS .100. THE SRM DOES NOT SAY YOU CANNOT REWORK DENTS OF THAT THICKNESS, BUT IT DOES NOT SAY YOU CAN. THE DENT HAS BEEN REWORKED AND IS WITHIN LIMITS. THE ENGINEERING DEPT IS GOING TO CLARIFY THE MANUALS AFTER CONFERRING WITH BOEING. SUPPLEMENTAL INFO FROM ACN 506195: IT WAS DETERMINED THAT THE DAMAGE WAS OUT OF LIMITS PER SRM 54-10-01 PAGE 104. THE ACTUAL DAMAGE WAS 7 INCHES LONG X 1 1/2 INCHES WIDE X 3/32 INCHES DEEP. TO CONFORM TO SRM LIMITS, THE DAMAGE NEEDED TO HAVE A FACTOR OF 30, MEANING THE DEPTH WAS 1/13 OF THE MINOR WIDTH. WE ATTEMPTED TO GET AN ENGINEERING VARIANCE AUTH TO DEFER THE DAMAGE, BUT WE WERE UNSUCCESSFUL. COMMERCIAL MAINT ORGANIZATION SUGGESTED TO EITHER LESSEN THE DEPTH OF THE DAMAGE BY DRILLING A HOLE AND USING A SLIDE HAMMER TO PULL THE DENT OUT, OR INCREASE THE WIDTH OF THE DAMAGE AND THUS INCREASE THE FACTOR AND MAKE ALLOWABLE PER SRM 54-10-01 PAGE 104. I OPTED TO DO THE LATTER. IN OTHER WORDS, I POUNDED THE DENT AND MADE IT WIDER. AT THAT POINT THE DAMAGE WAS WITHIN SRM 54-10-01 LIMITS, AND THE DAMAGE WAS DEFERRED LONG TERM, AND THE COWL WAS TO BE REPLACED AT 'C' CHK. THE CAPT REFUSED THE ACFT, THE FLT CONSEQUENTLY CANCELED. ON MAR/XA/01 I FOUND OUT THAT THE ORIGINAL DAMAGE WAS ALLOWABLE (MAINT MANUAL 51-00-99 PAGE 201) UP TO 0.25 INCHES DEEP. BUT, WE HAD REWORKED THE AREA WHICH WAS IN VIOLATION OF MAINT MANUAL 51-70-01 PAGE 1, PARAGRAPH 2C. THE ACFT MAINT FERRIED (NON REVENUE) TO XYZ FOR REPLACEMENT OF THE NOSE COWL.

Data retrieved from NASA's ASRS site as of July 2007 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.