AD 99-15-14
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Helicopter Transport Services, Inc. | CH-54B | Airworthiness Directives; Sikorsky Aircraft-Manufactured Model CH-54B Helicopters |
Unsafe Condition
Failure of the main gearbox second stage lower planetary plate (plate) due to fatigue cracking, which could lead to failure of the main gearbox and subsequent loss of control of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect the main oil filter daily for magnesium contamination and replace the main gearbox assembly if found. Conduct borescope inspections of the plate every 200 hours TIS, starting within 100 hours after the effective date. Inspect, rework, or replace the plate during main gearbox overhaul including machining, shot peening, and marking per specified standards.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within 100 hours TIS after the effective date for initial borescope inspection. Daily inspections required prior to each flight.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Aircraft-manufactured Model CH-54B helicopters with main gearbox second stage lower planetary plate part number 6435-20516-101 installed.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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