AD 52-28-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Scotts-Bell 47 Inc | 47B | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47B3 | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D1 | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
Unsafe Condition
Tail rotor pinion shaft, P/N 30-613-361, may have damage or cracks originating from the keyway or fillet area, leading to failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Magnetically inspect the tail rotor pinion shaft for damage or cracks. Replace immediately if worn, damaged, cracked, or fails inspection. If acceptable, rework recesses at each side of bearing boss with a 1/8-inch grinding wheel to create 0.030 to 0.040 inch radius at recess bottoms, ensuring reworked diameters do not drop below 0.763 inch and 0.604 inch respectively, and recess widths do not exceed 0.140 inch.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
as soon as possible, but not later than January 10, 1953
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Affected Aircraft
Bell Model 47B, 47B3, 47D and 47D1 Helicopters (Prior to Serial Number 477)
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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