1、Lessons Learned Entry: 1262Lesson Info:a71 Lesson Number: 1262a71 Lesson Date: 2002-07-01a71 Submitting Organization: LARCa71 Submitted by: Grant WatsonSubject: Pre-test Analysis Considered Only Static Loads, but Dynamic Loads Were Thought to Contribute to the Mishap Description of Driving Event: Wh
2、ile testing at Mach 0.8 in the 16-ft Transonic Tunnel (16 TT), a full-scale F-15 inlet model separated from the sting. The model traveled downstream and impacted the catch screen and turning vanes. The impact resulted in total loss of the model and damage to the screen. Some debris passed through th
3、e screen and damaged the wind tunnel blades. The sting was also damaged. An investigation team concluded that the aerodynamic loads on the model resulted in sting loads that exceeded the ultimate strength of the sting. Possible reasons the large loads occurred are: operating at a Mach Number not in
4、the original test envelope, F-15 cowl traveled past intended angle, sting deflection, and dynamic loads. Lesson(s) Learned: The pre-test analysis only considered static loads. The mishap investigation team concluded that the nature of the model/mount configuration required a dynamic analysis.Recomme
5、ndation(s): A method/analysis that accounts for dynamic loads should be used. Evidence of Recurrence Control Effectiveness: An electronic countermeasures device called a Model Protection Shutdown System (MPSS) is now in place at the facility. This PC-based instrumentation data gathering system monit
6、ors the actual static and dynamic loads on the model “real time“ via the six component strain gage balance. The Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-balance is the primary aerodynamic load path through the model/mount system. Preset warnin
7、g and interlock limits are determined during the pre-test phase of the test process and implemented prior to the first test runs. If combined static and dynamic load limits are experienced during the test runs, the MPSS will initiate an interlock or “trip“ that automatically reduces aerodynamic forc
8、es on the model. The branch has implanted new policy guidelines, which define specifically the operator and test engineer response to these limits.Documents Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Test FacilityAdditional Info: Approval Info: a71 Approval Date: 2002-07-22a71 Approval Name: Leslie J. Johnsona71 Approval Organization: LARCa71 Approval Phone Number: 757-864-9409Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
