AD 68-04-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Bell Helicopter Textron Canada Limited | 206A | Airworthiness Directives; Bell Model 206A Helicopters |
Unsafe Condition
Failure of the exhaust stack clamps which attach the exhaust ducts to the engine exhaust flanges could cause hazardous damage to the main rotor or the tail rotor.
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Required Actions
Replace exhaust stack clamps P/N N3657 with National Utilities Corporation P/N 4656AA. Install new clamps with studs facing outboard, tighten nuts evenly to 30 inch-pounds, and safety wire nuts using P/N MS20995C32. Repeat torque checks until torque is maintained at 30 inch-pounds after shaking the stack and tapping the clamp with a plastic mallet.
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Compliance Time
within the next 25 hours time in service after the effective date of this Airworthiness Directive
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Affected Aircraft
Bell Helicopter Textron Canada Limited Model 206A Helicopters, Serial Numbers 4 through 110, 112 through 116, 118, 119, 122, 124 through 126, 128, 129 and 133.
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Federal Register Abstract
Exhaust Stack Clamp Failure
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_68-04-02.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 68-04-02 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 206A Helicopters Subject: Exhaust Stack Clamp Failure Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 03/15/1968 Make: Bell Helicopter Textron Canada Limited Model: 206A Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 68-04-02 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-555 AD NUMBER: 68-04-02 SUBJECT HEADING: Airworthiness Directives; Bell Model 206A Helicopters ACTION: SUMMARY: DATES: Effective March 15, 1968. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 68-04-02 BELL: Amdt. 39-555. Applies to Model 206A Helicopters, Serial Numbers 4 through 110, 112 through 116, 118, 119, 122, 124 through 126, 128, 129 and 133. Compliance required within the next 25 hours time in service after the effective date of this Airworthiness Directive, unless already accomplished in accordance with Bell Helicopter Service Letter, Model 206A No. 38, dated January 10, 1968. To prevent possible hazardous damage to the main rotor or the tail rotor due to failure of the exhaust stack clamps which attach the exhaust ducts to the engine exhaust flanges, accomplish the following modification: Replace exhaust stack clamp as follows: Remove clamps, P/N N3657, from the exhaust stacks. Install two new clamps, National Utilities Corporation, P/N 4656AA, on exhaust stacks with studs facing outboard. Tighten the two nuts on each clamp evenly until each nut is finger tight. Torque nuts to 30 inch pounds. Grasp top of stack and shake, at the same time tap clamp lightly with a plastic mallet and then recheck torque. Repeat this procedure until torque can be maintained at 30 inch pounds. Safety wire nuts to stud shanks with safety wire, P/N MS20995C32. This amendment becomes effective on March 15, 1968. FOOTER:
Document Text
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AD Final Rules - DRS_68-04-02.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 68-04-02 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 206A Helicopters Subject: Exhaust Stack Clamp Failure Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 03/15/1968 Make: Bell Helicopter Textron Canada Limited Model: 206A Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 68-04-02 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-555 AD NUMBER: 68-04-02 SUBJECT HEADING: Airworthiness Directives; Bell Model 206A Helicopters ACTION: SUMMARY: DATES: Effective March 15, 1968. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 68-04-02 BELL: Amdt. 39-555. Applies to Model 206A Helicopters, Serial Numbers 4 through 110, 112 through 116, 118, 119, 122, 124 through 126, 128, 129 and 133. Compliance required within the next 25 hours time in service after the effective date of this Airworthiness Directive, unless already accomplished in accordance with Bell Helicopter Service Letter, Model 206A No. 38, dated January 10, 1968. To prevent possible hazardous damage to the main rotor or the tail rotor due to failure of the exhaust stack clamps which attach the exhaust ducts to the engine exhaust flanges, accomplish the following modification: Replace exhaust stack clamp as follows: Remove clamps, P/N N3657, from the exhaust stacks. Install two new clamps, National Utilities Corporation, P/N 4656AA, on exhaust stacks with studs facing outboard. Tighten the two nuts on each clamp evenly until each nut is finger tight. Torque nuts to 30 inch pounds. Grasp top of stack and shake, at the same time tap clamp lightly with a plastic mallet and then recheck torque. Repeat this procedure until torque can be maintained at 30 inch pounds. Safety wire nuts to stud shanks with safety wire, P/N MS20995C32. This amendment becomes effective on March 15, 1968. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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