AD 98-21-17
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-100 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B SUD Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200B Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200C Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200F Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-300 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400D Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400F Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
Unsafe Condition
Fatigue cracking of the spring beams on the outboard struts could result in loss of an outboard strut.
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Required Actions
Perform a detailed visual inspection to detect fatigue cracking of the spring beams on the outboard struts, and replace cracked spring beams with new or serviceable ones. Replace all spring beams with new improved spring beams in accordance with Boeing Service Bulletin 747-54-2177 to terminate repetitive inspections.
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Compliance Time
Prior to the accumulation of 10,000 total flight cycles, or within 18 months after the effective date of this AD, whichever occurs later.
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Affected Aircraft
Boeing Model 747 series airplanes, line numbers 202 through 396 inclusive, equipped with Pratt & Whitney Model JT9D-70 engines.
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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