AD 50-09-01
final rule
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | AT-6 (SNJ-2) | Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft |
| aircraft | The Boeing Company | AT-6A (SNJ-3) | Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft |
| aircraft | The Boeing Company | AT-6B | Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft |
| aircraft | The Boeing Company | AT-6C (SNJ-4) | Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft |
| aircraft | The Boeing Company | BC-1A | Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft |
Unsafe Condition
Cracked stabilizer spar fittings and improper installation of shims may result in structural failure of the horizontal stabilizer connection.
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Required Actions
Inspect horizontal stabilizer rear spar connection for cracked fittings and shim installation. Replace cracked or preset fittings with new 24 ST or X4130 bar stock fittings. Fabricate and install 24ST shims with specified dimensions and thickness to ensure proper fit.
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Compliance Time
prior to original certification
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Affected Aircraft
North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft (Army models) and SNJ-2, SNJ-3, and SNJ-4 Aircraft (Navy models)
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Federal Register Abstract
Stabilizer Spar Fittings and Shims
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_50-09-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 50-09-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft Subject: Stabilizer Spar Fittings and Shims Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: The Boeing Company Model: AT-6 (SNJ-2) | AT-6A (SNJ-3) | AT-6B | AT-6C (SNJ-4) | BC-1A Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 50-09-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 50-09-01 SUBJECT HEADING: Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 50-09-01 NORTH AMERICAN: Applies to all Army Model BC-1A, AT-6, -6A, -6B, - 6C; Navy SNJ-2, -3 and -4 Aircraft. To be accomplished prior to original certification. Inspect the horizontal stabilizer rear spar connection for cracked fittings and the installation of shims as follows: (1) Remove the fuselage to vertical stabilizer fairing assembly and the rear fairing assemblies at the horizontal stabilizer. (2) Remove the 1/4-inch bolts which attach the rear spar connection fitting to the spar assembly. (3) Remove paint from connection fittings and inspect for cracks. Check with a machinist's square or other means to determine if fitting is preset. Replace any cracked or preset fitting and repaint all others. New fittings may be made of 24 ST or X4130 bar stock to the same dimensions as the old fittings. (4) Inspect the fit between the spar and the sides of the base fitting with a feeler gage. Also inspect the fit between fitting P/N 77-21021 and the spar. If gaps exist, shims are necessary. (5) Fabricate 24ST shims 3 1/8 inches x 15/16 inch and of necessary thickness, and place on either side of spar flanges maintaining a parallel overall dimension to fit inside of fitting P/N 77-21021 within maximum clearance of 0.010. (6) Drill holes through the shims to match those in the fitting. Remove all chips and reinstall the various parts. (North American Service Bulletin dated March 6, 1946, covers this subject also.) This supersedes AD 45-44-03. FOOTER:
Document Text
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AD Final Rules - DRS_50-09-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 50-09-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft Subject: Stabilizer Spar Fittings and Shims Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: The Boeing Company Model: AT-6 (SNJ-2) | AT-6A (SNJ-3) | AT-6B | AT-6C (SNJ-4) | BC-1A Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 50-09-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 50-09-01 SUBJECT HEADING: Airworthiness Directives; North American Models Model BC-1A, AT-6, AT-6A, AT-6B, and AT-6C Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 50-09-01 NORTH AMERICAN: Applies to all Army Model BC-1A, AT-6, -6A, -6B, - 6C; Navy SNJ-2, -3 and -4 Aircraft. To be accomplished prior to original certification. Inspect the horizontal stabilizer rear spar connection for cracked fittings and the installation of shims as follows: (1) Remove the fuselage to vertical stabilizer fairing assembly and the rear fairing assemblies at the horizontal stabilizer. (2) Remove the 1/4-inch bolts which attach the rear spar connection fitting to the spar assembly. (3) Remove paint from connection fittings and inspect for cracks. Check with a machinist's square or other means to determine if fitting is preset. Replace any cracked or preset fitting and repaint all others. New fittings may be made of 24 ST or X4130 bar stock to the same dimensions as the old fittings. (4) Inspect the fit between the spar and the sides of the base fitting with a feeler gage. Also inspect the fit between fitting P/N 77-21021 and the spar. If gaps exist, shims are necessary. (5) Fabricate 24ST shims 3 1/8 inches x 15/16 inch and of necessary thickness, and place on either side of spar flanges maintaining a parallel overall dimension to fit inside of fitting P/N 77-21021 within maximum clearance of 0.010. (6) Drill holes through the shims to match those in the fitting. Remove all chips and reinstall the various parts. (North American Service Bulletin dated March 6, 1946, covers this subject also.) This supersedes AD 45-44-03. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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