AD 51-20-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | UH-12 | Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft |
| aircraft | Hiller Aviation | UH-12A | Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft |
Unsafe Condition
Protrusion of the bushings from the collective pitch ballast system bracket P/N 31125-1, leading to reduced main rotor blade pitch range and restricted controllability.
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Required Actions
Visually inspect the collective pitch ballast system bracket P/N 31125-1 for protrusion of bushings P/N 31120-1 as soon as possible but not later than September 1, 1951, and every 25-hour inspection period thereafter. If protrusion occurs, rework the assembly by installing set screws per United Helicopters Mandatory Bulletin No. 19. Discontinue inspections after rework is completed.
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Compliance Time
As soon as possible but not later than September 1, 1951, and at each 25-hour inspection period thereafter
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Affected Aircraft
Hiller Models UH-12 (Serial Numbers 105 to 135, Inclusive) and UH-12A (Serial Numbers 136 to 176, Inclusive, and 178, 180 and 181) with the Collective Pitch Ballast System.
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Federal Register Abstract
Collective Pitch Ballast System Bracket
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_51-20-03.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-20-03 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft Subject: Collective Pitch Ballast System Bracket Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Hiller Aviation Model: UH-12 | UH-12A Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 51-20-03 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-20-03 SUBJECT HEADING: Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-20-03 HILLER: Applies to the following Aircraft: Model UH-12, Serial Numbers 105 to 135, Inclusive. (Incorporating the Collective Pitch Ballast System); Model UH-12A, Serial Numbers 136 to 176, Inclusive, and 178, 180 and 181. Compliance required as noted below. In order to preclude the possibility of protrusion of the bushings from the collective pitch ballast system bracket with resultant reduction of the pitch range of the main rotor blades and restricted controllability, the following should be accomplished: (a) As soon as possible but not later than September 1, 1951, and at each 25-hour inspection period thereafter, visually inspect the collective pitch ballast system bracket P/N 31125-1 for protrusion of either upper or lower bushing P/N 31120-1. Particular inspection should follow each application of grease to the bracket. (b) If the bushing(s) are found to be protruding, the assembly should be reworked by installing set screws in accordance with United Helicopters Mandatory Bulletin No. 19. (c) Inspection of the bracket as specified in part (a) may be discontinued after the rework described in part (b) has been accomplished. (Hiller Helicopters Mandatory Service Bulletin No. 19 covers this same subject.) FOOTER:
Document Text
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AD Final Rules - DRS_51-20-03.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-20-03 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft Subject: Collective Pitch Ballast System Bracket Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Hiller Aviation Model: UH-12 | UH-12A 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: 51-20-03 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-20-03 SUBJECT HEADING: Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-20-03 HILLER: Applies to the following Aircraft: Model UH-12, Serial Numbers 105 to 135, Inclusive. (Incorporating the Collective Pitch Ballast System); Model UH-12A, Serial Numbers 136 to 176, Inclusive, and 178, 180 and 181. Compliance required as noted below. In order to preclude the possibility of protrusion of the bushings from the collective pitch ballast system bracket with resultant reduction of the pitch range of the main rotor blades and restricted controllability, the following should be accomplished: (a) As soon as possible but not later than September 1, 1951, and at each 25-hour inspection period thereafter, visually inspect the collective pitch ballast system bracket P/N 31125-1 for protrusion of either upper or lower bushing P/N 31120-1. Particular inspection should follow each application of grease to the bracket. (b) If the bushing(s) are found to be protruding, the assembly should be reworked by installing set screws in accordance with United Helicopters Mandatory Bulletin No. 19. (c) Inspection of the bracket as specified in part (a) may be discontinued after the rework described in part (b) has been accomplished. (Hiller Helicopters Mandatory Service Bulletin No. 19 covers this same subject.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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