AD 81-18-02

final rule

Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters

AD Number
81-18-02
Status
final_rule
Effective Date
Product Category
aircraft
Docket
Unknown
FR Citation
This information is not available.
Technical illustration of a helicopter rotor hub assembly
Problem area Rotor system

Applicability

TypeManufacturerModelDetails
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12 Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12A Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12B Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12C Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12D Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12L Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12L4 Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12E Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
aircraft Hiller Aviation | Siam Hiller Holdings, Inc. UH-12E-L Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters

Unsafe Condition

Tail rotor skin cracks and loose rivets can lead to tail rotor failure.

AI-generated summary from the source AD text. Verify against the official source before acting.

Required Actions

Visually inspect tail rotor blades for cracks or loose rivets and replace with serviceable parts if found. Inspect four vent holes in tail rotor blades for obstructions, replace blade if root vent holes are blocked, and clear tip vent holes if unblocked. Conduct pre-flight visual checks of vent holes before each flight and take corrective actions if obstructions are found.

AI-generated summary from the source AD text. Verify against the official source before acting.

Compliance Time

Prior to further flight after the effective date of this AD

AI-generated summary from the source AD text. Verify against the official source before acting.

Affected Aircraft

Hiller Aviation and Siam Hiller Holdings, Inc. models UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12L, UH-12L4, UH-12E, UH-12E-L, including military models H-23F and OH-23G

AI-generated summary from the source AD text. Verify against the official source before acting.

Federal Register Abstract

Tail Rotor Skin Cracks

Applicability Source Text

Show captured applicability text from the source AD
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AD Number:
81-18-02
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
Subject:
Tail Rotor Skin Cracks
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
09/10/1981
Make:
Hiller Aviation | Siam Hiller Holdings, Inc.
Model:
UH-12 | UH-12A | UH-12B | UH-12C | UH-12D | UH-12L | UH-12L4 | UH-12E | UH-12E-L
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: 81-18-02
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:   39-4203

AD NUMBER:   81-18-02

SUBJECT HEADING:   Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters

ACTION:  

SUMMARY:  

DATES:   Effective September 10, 1981.

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:  
81-18-02 HILLER AVIATION: Amendment 39-4203. Applies to Hiller Model UH-12 series helicopters including military models H-23F and OH-23G, certificated in all categories.

Compliance required as indicated, unless already accomplished.

To prevent tail rotor skin cracks, accomplish the following:

(a) Prior to further flight after the effective date of this AD;

1) Visually inspect the tail rotor blades for skin cracks or loose rivets. If cracks or loose rivets are found, replace with like serviceable part prior to return to service.

2) Inspect the four vent holes in the tail rotor blades for obstruction as indicated in Part 2 of Hiller Aviation Service Bulletin UH-12-55-1 dated August 11, 1981. If either of the vent holes at the root end are found to be obstructed, remove the blade from service and replace with like serviceable part. If the root vent holes are found to be unobstructed, inspect the tip vent holes and clear of any obstruction prior to return to service.

(b) Prior to each flight after the inspections required by paragraph (a) of this AD, conduct a visual check to determine that the four vent holes are clear of obstruction. If obstructions are found, perform the appropriate corrective actions of paragraph (a) of this AD prior to further flight.

NOTE: The checks required by paragraph (b) of this AD may be performed by the pilot.

NOTE: For the requirements regarding recording compliance and method of compliance with this AD in the aircraft's permanent maintenance records, see FAR 91.173.

(c) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes or helicopters to a base for the accomplishment of inspections or modifications required by this AD.

(d) Alternative inspections, modifications or other actions which provide an equivalent level of safety may be used when approved by the Chief, Engineering and Manufacturing Branch, FAA Western Region.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Hiller Aviation, 2075 W. Scranton Avenue, Porterville, California 93257, telephone (209) 781-8000. These documents may also be examined at FAA Western Region Office, 15000 Aviation Boulevard, Hawthorne, California 90261 and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. 20591. A historical file on this AD, which includes the incorporated material in full is maintained by the FAA at its headquarters in Washington, D.C. and at FAA Western Region Office.

This amendment becomes effective September 10, 1981.

FOOTER:

Document Text

Show stored source text (verify against official source)
AD Final Rules - DRS_81-18-02.html
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Print/Save as PDF
Document Versions
 Feedback
Details
AD Number:
81-18-02
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters
Subject:
Tail Rotor Skin Cracks
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
09/10/1981
Make:
Hiller Aviation | Siam Hiller Holdings, Inc.
Model:
UH-12 | UH-12A | UH-12B | UH-12C | UH-12D | UH-12L | UH-12L4 | UH-12E | UH-12E-L
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: 81-18-02
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:   39-4203

AD NUMBER:   81-18-02

SUBJECT HEADING:   Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters

ACTION:  

SUMMARY:  

DATES:   Effective September 10, 1981.

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:  
81-18-02 HILLER AVIATION: Amendment 39-4203. Applies to Hiller Model UH-12 series helicopters including military models H-23F and OH-23G, certificated in all categories.

Compliance required as indicated, unless already accomplished.

To prevent tail rotor skin cracks, accomplish the following:

(a) Prior to further flight after the effective date of this AD;

1) Visually inspect the tail rotor blades for skin cracks or loose rivets. If cracks or loose rivets are found, replace with like serviceable part prior to return to service.

2) Inspect the four vent holes in the tail rotor blades for obstruction as indicated in Part 2 of Hiller Aviation Service Bulletin UH-12-55-1 dated August 11, 1981. If either of the vent holes at the root end are found to be obstructed, remove the blade from service and replace with like serviceable part. If the root vent holes are found to be unobstructed, inspect the tip vent holes and clear of any obstruction prior to return to service.

(b) Prior to each flight after the inspections required by paragraph (a) of this AD, conduct a visual check to determine that the four vent holes are clear of obstruction. If obstructions are found, perform the appropriate corrective actions of paragraph (a) of this AD prior to further flight.

NOTE: The checks required by paragraph (b) of this AD may be performed by the pilot.

NOTE: For the requirements regarding recording compliance and method of compliance with this AD in the aircraft's permanent maintenance records, see FAR 91.173.

(c) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes or helicopters to a base for the accomplishment of inspections or modifications required by this AD.

(d) Alternative inspections, modifications or other actions which provide an equivalent level of safety may be used when approved by the Chief, Engineering and Manufacturing Branch, FAA Western Region.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Hiller Aviation, 2075 W. Scranton Avenue, Porterville, California 93257, telephone (209) 781-8000. These documents may also be examined at FAA Western Region Office, 15000 Aviation Boulevard, Hawthorne, California 90261 and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. 20591. A historical file on this AD, which includes the incorporated material in full is maintained by the FAA at its headquarters in Washington, D.C. and at FAA Western Region Office.

This amendment becomes effective September 10, 1981.

FOOTER:

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Retrieved: Apr 8, 2026

Rights: U.S. Government Public Domain

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