Narrative:

Three out of four of my past flights now have had significant delays due the known issue of 'wheel well vapor barrier cracking.' I have personally found the first evidence of this in two aircraft in our fleet with this cracking issue. It is referred to and repaired in accordance with (in accordance with) boeing structural repair manual (srm) 57-10-10-1a2. Maintenance control advises we have now at least 24; B737 aircraft with this cracking issue. I am fully aware of the non-structural pertinence of this issue. I am; though; fully aware that boeing and all carriers are waiting until cracks are found before tending to them.herein lies the issues with rather large flight delays. I strongly suggest and request more proactive involvement by our maintenance personnel to find these cracks sooner by increased inspections. The current srm quoted above allows for a crack not to exceed 16 inches. I found last week (first report I might add on this particular aircraft X) a crack 17.5 inches long. Aircraft X was allowed to fly the next day after engineering issued a line authorization. Aircraft X was taken out of service while waiting for this engineering issuance arrival. The longest crack now allowed has been extended to 17.5 inches; directly due to my discovery of this crack on aircraft X.this morning; I found aircraft Y with a crack in the left wheel well (aircraft X was in the right wheel well). Just as in aircraft X; aircraft Y had a smaller crack 7 inches [long] and my discovery was; again; the first report of vapor barrier cracking on aircraft Y. The third; aircraft Z; I found cracking had an approximately 4 inch extended crack beyond a previously repaired section. I found the crack progression on that aircraft last week. I have found that these cracks do not stop progressing until they hit the bottom of the vapor barrier and finally run almost to the top; on a 45-degree angle; running inboard and upward. An interesting thing I saw this morning on aircraft Y; that I highly recommend boeing engineers look at; is the approximate 6 x 6 inch open area of first theoretical cracking in the right wheel well; as of yet un-cracked; I noticed that this area was significantly deformed. The center of the area was 'oil canned' forward; away from the wheel well. If one would put a straight edge across the area; I estimated the distortion was on the order of approximately 3/16 of an inch. Thereby; indicating a great amount of stress in that area. It is obvious that in very short order; this area will also be cracked as the left wheel was this morning and the exact area was cracked on aircraft X.please see the following description. Note: the most displaced part of the crack running from upper left to bottom right. The physical dimension of the crack seen at this point is just over 6 inches. This is viewed from the right wheel well; standing in the center of the wheel well; facing forward. Crack is approximately; directly in front of a 6 foot tall man's right collar bone and the far outboard; lower edge of the crack; is at the bottom of the vapor barrier panel. There are three vertical rivets on a bulkhead fitting. In between the middle rivet and the next rivet to the right that is in a vertical row of six rivets on a vertical former; the upper edge of the crack can be seen as a 45-degree angle sloping down from upper left to bottom right; again just to the right of the middle left three rivets. This is the far upper left edge of the crack and ends under the bulkhead fitting. Again; this crack was objectively measured by two mechanics to be 17.5 inches long and is now the maximum allowed crack; regarding this issue; by boeing.a very descriptive service bulletin is greatly needed with inspections made routinely. Our operation is being severely effected. I am always available on my own time to assist in any way I can.

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Original NASA ASRS Text

Title: A pilot reports numerous B737 NexGen aircraft are being found with lower fuselage body fairings cracking in the vertical sections that support the left and right main wheel well vapor barrier blade seals. The blade seals are attached to the inside area of the fiberglass fairing.

Narrative: Three out of four of my past flights now have had significant delays due the known issue of 'wheel well vapor barrier cracking.' I have personally found the first evidence of this in two aircraft in our fleet with this cracking issue. It is referred to and repaired In Accordance With (IAW) Boeing Structural Repair Manual (SRM) 57-10-10-1A2. Maintenance Control advises we have now at least 24; B737 aircraft with this cracking issue. I am fully aware of the non-structural pertinence of this issue. I am; though; fully aware that Boeing and all carriers are waiting until cracks are found before tending to them.Herein lies the issues with rather large flight delays. I strongly suggest and request more proactive involvement by our Maintenance personnel to find these cracks sooner by increased inspections. The current SRM quoted above allows for a crack not to exceed 16 inches. I found last week (first report I might add on this particular aircraft X) a crack 17.5 inches long. Aircraft X was allowed to fly the next day after Engineering issued a Line Authorization. Aircraft X was taken out of service while waiting for this Engineering issuance arrival. The longest crack now allowed has been extended to 17.5 inches; directly due to my discovery of this crack on aircraft X.This morning; I found Aircraft Y with a crack in the left wheel well (aircraft X was in the right wheel well). Just as in aircraft X; aircraft Y had a smaller crack 7 inches [long] and my discovery was; again; the first report of vapor barrier cracking on aircraft Y. The third; aircraft Z; I found cracking had an approximately 4 inch extended crack beyond a previously repaired section. I found the crack progression on that aircraft last week. I have found that these cracks do not stop progressing until they hit the bottom of the vapor barrier and finally run almost to the top; on a 45-degree angle; running inboard and upward. An interesting thing I saw this morning on aircraft Y; that I highly recommend Boeing Engineers look at; is the approximate 6 x 6 inch open area of first theoretical cracking in the right wheel well; as of yet un-cracked; I noticed that this area was significantly deformed. The center of the area was 'oil canned' forward; away from the wheel well. If one would put a straight edge across the area; I estimated the distortion was on the order of approximately 3/16 of an inch. Thereby; indicating a great amount of stress in that area. It is obvious that in very short order; this area will also be cracked as the left wheel was this morning and the exact area was cracked on aircraft X.Please see the following description. Note: the most displaced part of the crack running from upper left to bottom right. The physical dimension of the crack seen at this point is just over 6 inches. This is viewed from the right wheel well; standing in the center of the wheel well; facing forward. Crack is approximately; directly in front of a 6 foot tall man's right collar bone and the far outboard; lower edge of the crack; is at the bottom of the vapor barrier panel. There are three vertical rivets on a bulkhead fitting. In between the middle rivet and the next rivet to the right that is in a vertical row of six rivets on a vertical former; the upper edge of the crack can be seen as a 45-degree angle sloping down from upper left to bottom right; again just to the right of the middle left three rivets. This is the far upper left edge of the crack and ends under the bulkhead fitting. Again; this crack was objectively measured by two mechanics to be 17.5 inches long and is now the maximum allowed crack; regarding this issue; by Boeing.A very descriptive Service Bulletin is greatly needed with inspections made routinely. Our operation is being severely effected. I am always available on my own time to assist in any way I can.

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.