| 11. | American Airlines, 284 planes, one jackscrew lacked lubricant, relubed.
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| 12. | Jackscrews are rarely replaced, the NTSB's Benjamin Berman said.
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| 13. | The jackscrew's threads were found to be stripped.
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| 14. | A jackscrew or car jack is a familiar mechanical actuator.
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| 15. | The last two are the ones with jackscrew problems.
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| 16. | The failure of the jackscrew was unprecedented as a cause of a crash.
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| 17. | The jackscrews on its jets showed surprising little wear.
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| 18. | Spokespeople for Northwest and Delta Air Lines also reported residue on their jackscrews.
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| 19. | The nut is kept still and mechanics see how far the jackscrew can wiggle.
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| 20. | Readings in excess of above are cause for replacement of acme jackscrew and nut.
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