AD 78-21-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-58BT | Airworthiness Directives; Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-58DT | Airworthiness Directives; Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-58ET | Airworthiness Directives; Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-58FT | Airworthiness Directives; Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-58HT | Airworthiness Directives; Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-58JT | Airworthiness Directives; Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT Helicopters |
Unsafe Condition
Tail rotor instability due to insufficient abrasion protection on tail rotor blades and inadequate control rod assembly.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install improved abrasion strips using Sikorsky Modification Kit 58070-10008-011 on specified tail rotor blades and install Sikorsky control rod assembly P/N 58400-64010-101.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
within 200 hours time in service or three months, whichever comes first, after the effective date of this AD
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Affected Aircraft
Sikorsky Models S-58BT, S-58DT, S-58ET, S-58FT, S-58HT, and S-58JT helicopters certificated in all categories.
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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