Minutes
From 2 July ART Meeting 1:
The
Tracker ART met 2 July via telecom. The
review process has been segmented into three fundamental steps:
1.
Understand the failure, data available, analysis results, probable cause's)
2.
Review & concur on likely cause's), review candidate corrective actions
3.
Review selected corrective action plan, evaluate associated risks &
mitigations
The
objective of the first meeting was to focus on Step 1. Robert Johnson reviewed the sequence of
events related to the Tracker Pre-engineering-Model Proto-Flight Tower-Module
Testing as documented in LAT-TD-00793.
The ART
requested additional information on available test data (LAT-TD-00788) and
results from insert pull out tests.
Significant discussion occurred with respect to manufacturing processes
associated with the carbon-carbon material as well as design practices
associated with the use of inserts and design load path redundancy.
The ART
also questioned whether we were sure that the AMES Test facility provided the
expected input for each test. The tracker Team has reviewed the test set-up and it is understood
that the Test environment was as expected.
The ART
questioned whether a Stress Factor of 2.1 was appropriate for the selected
material, this question will be reviewed again as part of the corrective action
recommendations
The ART
concluded that the ability to analytically reproduce the failure scenario
during the test(s) was unlikely due to the unknowns in structure condition
during the failure for the first test (as screws backed out) and the going in
structural integrity of the Pre-Engineering Model for the second test due to
the known crack. In addition, it was
agreed that no further information could be extracted from the existing test
data.
The ART
is considering a recommendation for further analysis by HYTEC to evaluate
Tracker Load paths with various non-participating inserts. The concern is that industry experience
indicates that tolerance build-ups can result in one or more attach points not
carrying the expected load resulting in increased loads at other points, this
may have been a contributing factor in the failure.
The ART
members are requested to email any summary concerns, issues, comments from this
first meeting to Dick Horn for inclusion in the ART report.
The ART
concluded that the primary objectives of the meeting were satisfied with
respect to understanding the failure and data available. The next meeting will be focused on
probably/likely cause(s) and review of candidate corrective actions.
Action
Items:
ART-1: Provide ART with test result data from
Vibration Tests (LAT-TD-00788) - Horn Closed (See Attachment)
ART-2: Provide ART results of insert pull out tests
- Johnson - Open (ECD NLT 8 July)
ART-3: Provide ART the properties for the
carbon-carbon material - Johnson - Open (ECD NLT 8 July)
ART-4: Provide a recommendation for design practice
and analysis cases for redundant load path considerations - Rodini - Open (ECD
NLT 8 July)
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Please
provide any corrections to these minutes and Action Item responses to Dick Horn