# AD T85-21-51: Airframe Self-Locking Nuts

- Type: Airworthiness directive
- Status: Historical
- Products: Boeing 767 Series (all)
- Superseded by: [AD 85-21-51](https://openairdocs.org/ad/85-21-51)
- Product type: Aircraft, Large airplane
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1C0DD96119B4C18F862568AA005DFFA0.0001
- DRS record last changed: August 7, 2025
- Page: https://openairdocs.org/ad/T85-21-51

## The airworthiness directive

T85-21-51 BOEING: Telegram issued October 25, 1985. Applicable to Boeing 767 series airplanes certificated in any category.

To prevent loss of certain critical airframe self-locking nuts accomplish the following unless previously accomplished:

A. Within 35 landings or 10 days after the effective date of this AD whichever occurs first inspect the horizontal elevator self-locking nuts in accordance with Boeing Alert Service Bulletin 767-27A0064 dated 10/25/85 or later FAA-approved revision. Self-locking nuts found to be insecure in accordance with the criteria specified in the service bulletin must be replaced before further flight with serviceable self-locking nuts.

B. Within 50 landings or 20 days after the effective date of this AD whichever occurs first, inspect the inboard aft trailing edge flap self-locking nuts and the outboard wing spoiler actuator self-locking nuts in accordance with Boeing Alert Service Bulletin 767-27A0064 dated 10/25/85 or later FAA-approved revision. Self-locking nuts found to be insecure in accordance with the criteria specified in the service bulletin must be replaced before further flight with serviceable self-locking nuts.

C. Alternate means of compliance which provide an acceptable level of safety may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.

The Boeing service bulletin specified in this directive may be obtained upon request to the Boeing Company, P.O. Box 3707, Seattle, Washington 98124.

This airworthiness directive becomes effective upon receipt.

## Registered aircraft it may apply to (OpenAirDocs)

No registered aircraft matched the models it names.

## Related documents

- [AD 85-21-51](https://openairdocs.org/ad/85-21-51): Elevator Actuator Rod End Bolt Retaining Nuts · Boeing 767-200 Series. Effective Feb 24, 1986. Supersedes this AD

Its text cites no advisory circulars or STCs.

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