Some Briefs From the Federal Register and ADs. See source Links for full texts.
2002. Inadequate Level Of Safety - lap Joints.
AD- 2002-07-08. 737-200, -200C, -300, -400, and -500 series airplanes having line numbers 292 through 2565 inclusive
that currently requires repetitive inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage
also requires modification of the fuselage lap joints at certain locations,
. This amendment is prompted by the FAA's determination that, in light of additional crack findings, certain modifications of the fuselage lap joints do not provide an adequate level of safety. Compliance; before the accumulation of 50,000 total flight cycles or within 2,250 flight cycles after the effective date of this AD, whichever comes later. Locations; lower skin at the lower row of fasteners in the lap joints of the fuselage, - stringers 4R and 10R
Source;
http://www.airweb.faa.gov/Regulatory...ILE/020708.pdf
2005. Fuselage Structure Tests Failures at 21,000 cycles.
AD- 2005-13-27. 737-300, -400, and -500 series airplanes.
. repetitive inspections for cracking of the crown area of the fuselage skin,
.. prompted by a Model 737 fuselage structure test and fatigue analysis that indicate fuselage skin cracking could occur between 21,000 and 42,000 total flight cycles.. . Within 4,500 cycles. Effective August 1, 2005.
Source;
http://www.airweb.faa.gov/Regulatory...2005-13-27.pdf
2006. 757s. Countersinks Too Deep.
2006-20-11. 757-200, -200PF, and -200CBs.
.requires doing initial and repetitive detailed or high frequency eddy current inspections for cracks around the rivets at the upper fastener row of the skin lap splice of the fuselage, and repairing any crack found. This AD results
from a report indicating that certain rivets were incorrectly installed in some areas of the skin lap splices during production because
they were drilled with a countersink that was too deep. Boeing states that the production rivets are commonly referred to as ''Briles'' rivets, and are manufactured with a 120-degree, modified shear head.
Effective 11/8/2006.
Source;
http://www.airweb.faa.gov/Regulatory...2006-20-11.pdf
2008. Missing Or Loose Fasteners or Milled Steps.
AD- 2008-12-04. 737- 600, -700, -700C, -800, and -900 series airplanes.
.requires various repetitive inspections to detect cracks along the chemically milled steps of the fuselage skin or missing or loose fasteners in the area of the preventative modification or repairs,
. This AD results from a fatigue test that revealed numerous cracks in the upper skin panel at the
chemically milled step above the lap joint. Compliance per the Service Bulletin. Within 36 months. Effective July 16, 2008.
Source; http://www.airweb.faa.gov/Regulatory...2008-12-04.pdf
2011. 100 ADs - Widespread Fatigue Damage .
Since 1988, the FAA has issued approximately 100 airworthiness directives to address WFD
Widespread Fatigue Damage in airplanes. Approximately 25 percent of these airworthiness directives were too urgent to allow the public an opportunity to comment in advance. These airworthiness directives required inspections, and the FAA later superseded the majority of them to expand the inspections or require modifications because inspections were not enough to preclude WFD. Effective January 14, 2011. Source; Federal Register;
http://www.regulations.gov/#!documentDetail;D=FAA-2006-24281-0088.