maintenance-penetrant-inspection-part-two- The crack was large enough to detect it during the last FPI of the operator before the flight accident. - There are serious questions regarding the reliability of the drying process ("flash drying") used to remove rinsing water out of the cracks. Water that remains in the cracks prevents the testing fluid from entering them, thereby making crack detection difficult or impossible. - Better techniques are necessary in order to ensure complete coverage of the bore wall with developing powder.- There was no system for the time control of the FPI process. This is a major shortcoming.- The FPI findings and their recognizability react sensitively to the handling, fastening, and bracing of the parts. This can prevent the inspector from noticing certain areas of the part.- One or more problems during cleaning and drying in the FPI process by the operator could have prevented detection of the crack. - These problems may also be present in other overhaul operations, and could be the reason that cracks remained undetected in other cases, as well. - There were no human or physical factors that prevented the inspector from finding the crack. - The apparenty failure of the inspector to seek systematic verifying subsequent tests, and to apply these to all surfaces of the disk if necessary, may have led to the crack being overlooked.- A low expectation of finding cracks in this part type may have prevented the FPI inspectors from registering the crack indicators and/or correctly evaluating them. - The duration of the inspection and the time requirements of subsequent steps may have affected the effectiveness of the inspector. - The great potential danger of an overlooked crack in a critical part requires the testing of FPI personnel with regard to their ability to recognize and document flaws. - The overlooking of the crack by the operator is either due to an error during cleaning and the FPI process, an failure by the inspector to recognize the crack, or a combination of these influences. - Previous finishing and the inspection process by the operator do not guarantee that titanium alloy rotor parts will be flaw-free over their entire life span. All critical titanium rotor parts are susceptible to finishing cracks. Subsequent crack growth during operation can lead to catastrophic accidents.