AD 74-25-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Lockheed Martin Corporation | 188A | LOCKHEED Model L-188A and L-188C Airplanes |
| aircraft | Lockheed Martin Corporation | 188C | LOCKHEED Model L-188A and L-188C Airplanes |
Unsafe Condition
Failure of the horizontal stabilizer due to fatigue cracks in the front spar at F.S. 1167.
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Required Actions
Perform a visual or eddy current inspection with dye penetrant confirmation of the front spar upper cap bolt hole at B.L. 28 L&R as per Lockheed Service Bulletin No. 88/SB 692. Depending on crack severity, repair or replace the spar cap segment per specified paragraphs of the service bulletin. Repeat inspections at intervals not exceeding 2500 flight hours unless preventive rework is done.
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Compliance Time
Within 300 additional flight hours after January 3, 1975, unless already accomplished within the last 2200 flight hours prior to this AD, and at intervals not to exceed 2500 flight hours thereafter.
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Affected Aircraft
Lockheed Model L-188A and L-188C airplanes certificated in all categories.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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