Narrative:

This aircraft; [eurocopter bk-117]; has a hole in the belly between the fuel pumps. The hole was there when we got the aircraft from the repair station in ZZZ. There is tribal knowledge that many; if not all; bk-117s have these holes. The aircraft has most likely been operating with this hole for years and years. There is a clamp on the fuel transfer tube that can seep. The hole is for access to the clamp; as opposed to removal of the cabin floor; which would otherwise be needed for access. I was informed by mechanic X that there was an issue with these holes. He told me that eurocopter had issued a 'no technical objection' (nto); requiring a daily tap test and repair in 50 hours. A daily tap test requirement indicated to mechanic X and me that this is a serious issue; so we took pictures of ours and sent to our manager for evaluation right away. We took the aircraft out of service until we received guidance from eurocopter.I do not recall ever seeing a bk-117 that did not have these holes. Our bk had this hole when it came from the repair station in ZZZ. Countless people; including [those] with far more experience than me had accepted this hole; so I did not believe that it was an improper repair until I heard from mechanic X. Nevertheless; I had signed-off the aircraft with this condition.I would suggest a service bulletin (sb) from eurocopter or possibly a maintenance bulletin from our company operations. When I talked to the [manufacturer] technical representative about our aircraft he said that there were many other aircraft having the same issue. The hole was known since october 2009. It was only identified as an issue april 2011.

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Original NASA ASRS Text

Title: Two mechanics report finding unapproved access holes in the lower belly section of the external fuselage skin of various Eurocopter BK-117 helicopters. The holes were used to access the fuel transfer tube attach clamps that tend to leak fuel when flying from warm weather to frigid winter weather states.

Narrative: This aircraft; [Eurocopter BK-117]; has a hole in the belly between the fuel pumps. The hole was there when we got the aircraft from the Repair Station in ZZZ. There is tribal knowledge that many; if not all; BK-117s have these holes. The aircraft has most likely been operating with this hole for years and years. There is a clamp on the fuel transfer tube that can seep. The hole is for access to the clamp; as opposed to removal of the cabin floor; which would otherwise be needed for access. I was informed by Mechanic X that there was an issue with these holes. He told me that Eurocopter had issued a 'No Technical Objection' (NTO); requiring a daily tap test and repair in 50 hours. A daily tap test requirement indicated to Mechanic X and me that this is a serious issue; so we took pictures of ours and sent to our Manager for evaluation right away. We took the aircraft out of service until we received guidance from Eurocopter.I do not recall ever seeing a BK-117 that did not have these holes. Our BK had this hole when it came from the Repair Station in ZZZ. Countless people; including [those] with far more experience than me had accepted this hole; so I did not believe that it was an improper repair until I heard from Mechanic X. Nevertheless; I had signed-off the aircraft with this condition.I would suggest a Service Bulletin (SB) from Eurocopter or possibly a Maintenance bulletin from our Company Operations. When I talked to the [Manufacturer] Technical Representative about our aircraft he said that there were many other aircraft having the same issue. The hole was known since October 2009. It was only identified as an issue April 2011.

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.