This invention relates to the safe, reliable, and repeatable testing under external load of the Extraction Force Transfer Coupling (EFTC) currently used in the extraction of airdrop platforms from both the C-17 and C-130 cargo transport aircraft. The invention enables functional testing of the EFTC at various loading angles and load magnitudes, as well as in different hardware configurations, to verify its performance in both nominal and off-nominal extraction scenarios.

The invention was created as part of the investigation into the failure of an EFTC to function during a NASA airdrop of an instrumented platform from a C-130 aircraft on February 9, 2010. The platform was destroyed because the EFTC coupling link assembly did not release the three-point link. This failure to release prevented the parachutes on the platform from deploying. A novel method to test the EFTC under external loading had to be invented in order to isolate the cause of the failure.

The test rig setup and operation include not only the EFTC, but also the transfer cable and External Force Transfer Actuator (EFTA). The transfer cable routing configuration along the platform was simulated, and a linear actuator attached to a Type XXVI nylon strap was used to load the threepoint link through a range of angles and magnitudes, both vertically and horizontally. The test rig included redundant Vectran lines that attenuated the energy imparted to the threepoint link after it released, and also restrained it from damaging itself or the surroundings.

The method enabled the ability to actuate the mechanism, apply an off-axis load, and repeatedly deploy and capture the three-point link. The nature of the test failure included loading conditions where the pull force was off-axis. This required that the test setup permit full deployment of the three-point link from the coupling link assembly in order to understand the dynamics of the mechanism release, and also a restraint system to prevent the link from becoming a projectile. A bumper absorbed the energy during the spring-back of the coupling link assembly.

This work was done by John Zipay of Johnson Space Center and Dale Jennings, Amber Newport, and Satish Reddy of Jacobs Technology. MSC-25041-1

NASA Tech Briefs Magazine

This article first appeared in the November, 2014 issue of NASA Tech Briefs Magazine.

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