Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD would require repetitive inspections to detect cracks in the vertical beam webs of the body station (BS) 178 bulkhead, and corrective actions if necessary. This proposed AD also would require a terminating modification for the repetitive inspections. This proposed AD results from reports of numerous cracks in the vertical beam webs. We are proposing this AD to prevent fatigue cracks in certain vertical beam webs, which could result in loss of structural integrity of the BS 178 bulkhead, and consequently could impair the operation of the control cables for the elevators, speed brakes, and landing gear, or could cause the loss of cabin pressure.