# AD 56-01-02: Wing Spar Splice Bolt Holes

- Type: Airworthiness directive
- Status: Current
- Products: Aero Spacelines 377, 377MG and 377SGT
- Published: December 4, 1956
- Issued: December 4, 1956
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 1 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/F1B322BE72365C1B8625682A00659AFD.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/56-01-02

## The airworthiness directive

56-01-02 BOEING: Applies to All model 377 Aircraft. Compliance required as indicated. As a result of cracks discovered at wing spar splice bolt holes the following inspection and possible rework is required. At the next basic check period and subsequent thereto, at each basic check period but not to exceed an interval of 2,500 hours flight time, the No. 1 bolt hole in each rear spar Station 246 joint and Nos. 1 and 6 bolt holes in each front and rear spar Station 510 joints shall be carefully inspected by use of borescope or equivalent method. If cracks are found, the splice should be reworked in accordance with instructions contained in Boeing Service Letter No. 289. Within the next 500 flight hours, unless recently accomplished, the outboard bolt holes in each front and rear spar Station 47.75 joints shall be inspected for cracks by use of borescope or equivalent method. If cracks are found, they shall be repaired in accordance with Boeing Instructions. This supersedes AD 55-23-01.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A-812](https://openairdocs.org/tcds/A-812): Aero Spacelines Incorporated; names 3 of 3 models: 377, 377MG, 377SGT

## 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: 1 (1 by airframe model, 0 by engine model)
- Makers: Boeing 1

Models with the most aircraft:

- [Boeing 377MG](https://openairdocs.org/model/boeing-377mg): 1 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/56-01-02/models.md
Every aircraft: https://openairdocs.org/ad/56-01-02/aircraft.md

Its text cites no advisory circulars or STCs.

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