# Proposed AD FAA-2008-0415: The Boeing Company Model 737 Airplanes

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2011-27-03
- Products: Boeing
- Product type: Aircraft
- Action: Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
- Published: April 19, 2011, 76 FR 21815
- Comments due: May 16, 2011
- Became: [AD 2011-27-03](https://openairdocs.org/ad/2011-27-03)
- Docket: FAA-2008-0415 (https://www.regulations.gov/docket/FAA-2008-0415, where comments are filed)
- Project: 2007-NM-256-AD
- FR document: 2011-9410
- Official PDF: https://openairdocs.org/files/sha256/01/f8/01f8e501c4ca908f6ca36b5babf64dcc071ffc4b2c7a2e4efd27a4792e19539b (from https://www.govinfo.gov/content/pkg/FR-2011-04-19/pdf/2011-9410.pdf)
- Federal Register: https://www.federalregister.gov/documents/2011/04/19/2011-9410/airworthiness-directives-the-boeing-company-model-737-airplanes
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/B90F69DDCD887B1686257877004970AC.0001
- Page: https://openairdocs.org/proposed/FAA-2008-0415

## Summary

We are revising an earlier proposed airworthiness directive (AD) for certain Model 737 airplanes. The original NPRM would have required repetitive inspections, lubrications, and repetitive repairs/ overhauls of the ball nut and ballscrew and attachment (Gimbal) fittings for the trim actuator of the horizontal stabilizer; various installation(s); and corrective actions if necessary; as applicable. The original NPRM resulted from a report of extensive corrosion of a ballscrew used in the drive mechanism of the horizontal stabilizer trim actuator (HSTA). This action revises the original NPRM by adding airplanes to the applicability. We are proposing this supplemental NPRM to prevent an undetected failure of the primary load path for the ballscrew in the drive mechanism of the HSTA and subsequent wear and failure of the secondary load path, which could lead to loss of control of the horizontal stabilizer and consequent loss of control of the airplane.

## Notices in this docket

- Apr 28, 2008: Notice of proposed rulemaking (NPRM). (first notice), FR document E8-9193, comments due Jun 12, 2008 (https://www.federalregister.gov/documents/2008/04/28/E8-9193/airworthiness-directives-boeing-model-737-airplanes)
- Apr 19, 2011: Supplemental notice of proposed rulemaking (NPRM); reopening of comment period., FR document 2011-9410, comments due May 16, 2011 (https://www.federalregister.gov/documents/2011/04/19/2011-9410/airworthiness-directives-the-boeing-company-model-737-airplanes)

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