FAA Orders Helicopter Owners to Inspect Potentially Cracked Transmission Parts
Published Date: 10/23/2026
Rule
Summary
If you own an MD Helicopters Model 369 or 500N, listen up! The FAA found some parts in the main transmission that might be cracked and unsafe. Starting November 27, 2026, you’ll need to check these parts once and replace them if needed to keep flying safe—no surprise costs, just a quick safety check.
Analyzed Economic Effects
2 provisions identified: 1 benefits, 1 costs, 0 mixed.
Mandatory inspection and replacement schedule
If you own or operate an MD Helicopters Model 369D, 369E, 369F, 369FF, 369H, or 500N with coupling P/N 369H5660, S/N 8564-0001 through 8564-0308, you must visually inspect each main transmission drive shaft coupling within 50 hours time-in-service (TIS) or 6 months after November 27, 2026, using a bright light and 10X magnification. If you find any spline cracks, you must remove and replace the coupling before further flight; if no cracks are found, you must replace the coupling within 300 hours TIS after the effective date. The FAA estimates the inspection costs $85 per helicopter and replacement (if needed) costs up to $3,532 per coupling (2 work-hours at $85/hour plus $1,681 parts).
Reduces risk of in-flight coupling failure
This AD is intended to find and remove mechanically damaged couplings that could develop fatigue cracks and fail. The FAA says an unrepaired damaged coupling could lead to loss of power to the main rotor and possible emergency autorotational landing, so the inspections and required replacements reduce that safety risk.
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