# Federal Register #2026-21664

FAA safety directive requires inspection and possible replacement of MD Helicopters drive shaft couplings

**Buyer:** Federal Aviation Administration (FAA)
**Posted:** October 23, 2026
**Identifier:** 2026-21664

The Federal Aviation Administration issued a safety directive for certain MD Helicopters aircraft; this is a regulatory requirement, not a solicitation for products or services.
- **Government agency:** U.S. Department of Transportation, Federal Aviation Administration (FAA); no specific office is identified.
- **OEMs named:** **MD Helicopters, LLC**, manufacturer of the affected helicopters and coupling; Boeing is mentioned only in connection with a separate Boeing 787 directive correction.
- **Affected aircraft and part:** MD Helicopters Model 369D, 369E, 369F, 369FF, 369H, and 500N helicopters equipped with main transmission drive shaft coupling P/N 369H5660, serial numbers 8564-0001 through 8564-0308. The FAA estimates 568 U.S.-registered helicopters are affected.
- **Required action:** Inspect each affected coupling once for spline cracks using a bright light and 10X magnification. Complete inspection within 50 hours time-in-service or six months, whichever comes first.
  - If cracks are found, replace the coupling before further flight.
  - If no cracks are found, replace the coupling within 300 hours time-in-service.
- **Procurement status:** No products or services are being solicited, and no purchase quantity or contract value is specified.

### Description

The FAA is adopting a final rule for certain MD Helicopters, LLC Model 369D, 369E, 369F, 369FF, 369H, and 500N helicopters with specified main transmission drive shaft couplings. The rule requires a one-time visual inspection of the couplings for spline cracks within 50 hours time-in-service or six months after the effective date, whichever comes first. If cracks are found, the affected coupling must be replaced before further flight; if no cracks are found, replacement is required within 300 hours time-in-service after the effective date. The FAA estimates the rule affects 568 U.S.-registered helicopters.

[View original listing](https://www.federalregister.gov/documents/2026/10/23/2026-21664/airworthiness-directives-md-helicopters-llc-helicopters)