# AD 74-25-04: Horizontal Stabilizer

- Type: Airworthiness directive
- Status: Current
- Products: Lockheed Martin 188A and 188C
- Effective: January 3, 1975
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Amendment: 39-2032
- Registered aircraft: 4 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/589FA6E82221EA59862569750048A811.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/74-25-04

## The airworthiness directive

74-25-04 LOCKHEED: Amendment 39-2032. Applies to all Lockheed model L-188A and L-188C airplanes certificated in all categories.

Compliance is required as indicated.

To prevent possible failure of the horizontal stabilizer due to fatigue cracks in the front spar at F.S. 1167, accomplish the following:

  (a) Within 300 additional flight hours after the effective date of this A.D., unless already accomplished within the last 2200 flight hours prior to this A.D., and at intervals not to exceed 2500 flight hours thereafter 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 depicted in Lockheed Service Bulletin No. 88/SB 692 dated October 30, 1974, by figure 1, view A-A. Perform this inspection per the accomplishment instructions in S.B. 88/SB 692 dated October 30, 1974, or later FAA- approved revisions.

  (1) If crack development is noted and the crack can be removed with a .50 inch maximum diameter clean up concentric with the bolt hole, accomplish the repair instruction of paragraph 2.E (1) of Service Bulletin 692.

  (2) If crack development is noted and the crack can be removed with a .84 inch maximum diameter clean up concentric with the bolt hole, accomplish the repair instruction of paragraph 2.E (2) of Service Bulletin 692.

  (3) Any crack development in the P/N 800344-1 spar cap, which exceeds the limitations of the .84 inch maximum diameter clean up requires the replacement of the spar cap segment per accomplishment instructions of paragraph 2.E (3) of Service Bulletin 692.

  (4) If the inspections reveal no crack development, repeat the inspection thereafter at intervals not to exceed 2500 flight hours, unless the preventive rework specified in paragraph 2D of Service Bulletin 692 is accomplished.

  (5) If the repairs or preventive rework listed in items 1 thru 4 are accomplished the repeat inspections at 2500 flight hours may be discontinued.

  (b) Equivalent inspections and installations may be approved by the Chief, Aircraft Engineering Division, FAA Western Region.

  (c) Aircraft may be operated per FARs 21.197 and 21.199 to a base for accomplishment of maintenance per this A.D.

This amendment is effective January 3, 1975.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 4A22](https://openairdocs.org/tcds/4A22): Lockheed Martin Corporation; names 2 of 2 models: 188A, 188C

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 4 (4 by airframe model, 0 by engine model)
- Makers: Lockheed 4

Models with the most aircraft:

- [Lockheed 188C](https://openairdocs.org/model/lockheed-188c): 3 aircraft (airframe model)
- [Lockheed 188A](https://openairdocs.org/model/lockheed-188a): 1 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/74-25-04/models.md
Every aircraft: https://openairdocs.org/ad/74-25-04/aircraft.md

Its text cites no advisory circulars or STCs.

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