1、Lessons Learned Entry: 0504Lesson Info:a71 Lesson Number: 0504a71 Lesson Date: 1994-07-12a71 Submitting Organization: LARCa71 Submitted by: Bernard LewisSubject: Improper Handling of a Test Item Ultimately Resulted in Test Failure Description of Driving Event: On January 15, 1991, a failure occurred
2、 in the 8 Transonic pressure tunnel during testing of a model wing with attached flap. During the test run, the flap peeled away from the wing, broke free, and proceeded down the tunnel. Extensive damage resulted.It is hypothesized that the east wall flap fitting pin was damaged when the flap was al
3、lowed to bend during installation. These pins are stainless steel and approximately 0.38“ square. They are inserted into square holes in the tunnel side plates. When the model was installed, the flap was lifted to complete the attachment, was left unsupported during the attachment process, and defle
4、cted in the center. This deflection could have caused the square flap fitting pin to become overstressed. The Metallic Materials Branch did, in fact, identify an area of tensile fracture related to a single load incident, but was unable to conclusively establish when the fracture occurred. In any ca
5、se, engineering should strive to use the lowest stress concentration configuration feasible. In this instance, a round pin on the flap end fitting would have reduced the stress concentrations from the level present on the square pins and perhaps prevented test failure.Lesson(s) Learned: Improper han
6、dling of a test item likely contributed to overstressing a fitting pin, leading to a tensile fracture of the pin and its subsequent failure, which ultimately resulted in test failure.Recommendation(s): Proper handling procedures were subsequently observed and there was no further failure attributed
7、to this cause.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Ground Operationsa71 Test FacilityAdditional Info: Approval Info: a71 Approval Date: 1997-04-02a71 Approval Name: Elijah C. Kenta71 Approval Organization: 421a71 Approval Phone Number: 757-864-3345Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
