FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes
One of the inspection checklist items:<p><i>Measure the clearance between the flapper bushings at both locations on each engine bleed air 5th stage check valve. If the clearance between the flapper bushings is a minimum of 0.004 inch (0.102 mm) at both locations, the engine bleed air 5th stage check valve at that location has passed this inspection.</i><p>I knew that aviation engineering dealt with tight tolerances, but boy, it must be difficult to make a call like that when you&#x27;re dealing with thousandths of an inch. Do field technicians have dependable tools and methods of measuring with such high degrees of precision?