AD 51-15-02

final rule

FRANKLIN Model 6A4-165-B3 Engines

AD Number
51-15-02
Status
final_rule
Effective Date
Product Category
engine
Docket
Unknown
FR Citation
This information is not available.
Technical illustration of an aircraft turbine engine assembly
Problem area Engine

Applicability

TypeManufacturerModelDetails
engine Wytwornia Sprzetu Komunikacyjnego 6A4-165-B3 FRANKLIN Model 6A4-165-B3 Engines

Unsafe Condition

Cracks in the crankcase webbing near the main journal area and at the main bearing stud hole, which could lead to crankcase fracture and engine failure.

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

Required Actions

Inspect the crankcase webbing near the main journal area for cracks. Replace crankcases with fractures or advanced cracks with P/N 18925 assembly. Inspect at 250-hour intervals if no cracks found, or 50-hour intervals if surface cracks or cracks near main bearing stud hole are detected.

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

Compliance Time

by July 15, 1951. Effective on and after this date, inspections required for engines with 500 hours of operation since new or 250 hours since last overhaul.

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

Affected Aircraft

Franklin Model 6A4-165-B3 Engines serial numbers 33046 and below with original crankcase assembly P/N 18553 (left half No. 18305; right half No. 18306).

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

Federal Register Abstract

Crankcase

Applicability Source Text

Show captured applicability text from the source AD
AD Final Rules - DRS_51-15-02.html
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Details
AD Number:
51-15-02
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
FRANKLIN Model 6A4-165-B3 Engines
Subject:
Crankcase
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
Make:
Wytwornia Sprzetu Komunikacyjnego
Model:
6A4-165-B3
Product Type:
Engine
Product Subtype:
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 51-15-02
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:  

AD NUMBER:   51-15-02

SUBJECT HEADING:   FRANKLIN Model 6A4-165-B3 Engines

ACTION:  

SUMMARY:  

DATES:  

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:   51-15-02 FRANKLIN: Applies to All Franklin 6A4-165-B3 Engines Serially Numbered 33046 and Below Incorporating Original Crankcase (Left Half No. 18305; Right Half No. 18306). These Two Parts Form Crankcase Assembly, P/N 18553. The Number of Each Crankcase Half is Located on Each Casting Below the Number 1 and 6 Cylinder Location.
To be accomplished by July 15, 1951.
Effective on and after this date, all applicable crankcases with 500 hours of operation since new or 250 hours since last overhaul should be inspected as follows: Remove crankcase cover and visually inspect the webbing near the main journal area for cracks.
(1) Crankcases found to be free of cracks should be inspected at 250-hour intervals thereafter. In the event that the conditions described in (2) and (3) are detected, the provisions of (2) and (3) will apply.
(2) Crankcases found with (a) surface indications, hairline cracks, or small wall cracks and (b) cracks starting at main bearing stud hole on the opposite side from main bearing support, may be operated further at the option of the owner. Such crankcases should be inspected at 50-hour intervals thereafter to determine progress of cracks.
(3) Crankcases found fractured or with cracks that have progressed to the extent that they enter the main bearing supports (usually from back near (a) main bearing stud hole and (b) drilled oil hole) indicate that a complete break soon will occur. Such crankcases should be replaced with the reinforced crankcase assembly, P/N 18925, at which time no further inspection is required.
Crankcase assembly P/N 18925 may be identified by casting No. 18905 appearing below No. 1 cylinder location and casting No. 18906 appearing below No. 6 cylinder location.
(Franklin Service News No. 10 also covers this subject.)

FOOTER:

Document Text

Show stored source text (verify against official source)
AD Final Rules - DRS_51-15-02.html
Copy URL
Print/Save as PDF
Document Versions
 Feedback
Details
AD Number:
51-15-02
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
FRANKLIN Model 6A4-165-B3 Engines
Subject:
Crankcase
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
Make:
Wytwornia Sprzetu Komunikacyjnego
Model:
6A4-165-B3
Product Type:
Engine
Product Subtype:
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 51-15-02
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:  

AD NUMBER:   51-15-02

SUBJECT HEADING:   FRANKLIN Model 6A4-165-B3 Engines

ACTION:  

SUMMARY:  

DATES:  

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:   51-15-02 FRANKLIN: Applies to All Franklin 6A4-165-B3 Engines Serially Numbered 33046 and Below Incorporating Original Crankcase (Left Half No. 18305; Right Half No. 18306). These Two Parts Form Crankcase Assembly, P/N 18553. The Number of Each Crankcase Half is Located on Each Casting Below the Number 1 and 6 Cylinder Location.
To be accomplished by July 15, 1951.
Effective on and after this date, all applicable crankcases with 500 hours of operation since new or 250 hours since last overhaul should be inspected as follows: Remove crankcase cover and visually inspect the webbing near the main journal area for cracks.
(1) Crankcases found to be free of cracks should be inspected at 250-hour intervals thereafter. In the event that the conditions described in (2) and (3) are detected, the provisions of (2) and (3) will apply.
(2) Crankcases found with (a) surface indications, hairline cracks, or small wall cracks and (b) cracks starting at main bearing stud hole on the opposite side from main bearing support, may be operated further at the option of the owner. Such crankcases should be inspected at 50-hour intervals thereafter to determine progress of cracks.
(3) Crankcases found fractured or with cracks that have progressed to the extent that they enter the main bearing supports (usually from back near (a) main bearing stud hole and (b) drilled oil hole) indicate that a complete break soon will occur. Such crankcases should be replaced with the reinforced crankcase assembly, P/N 18925, at which time no further inspection is required.
Crankcase assembly P/N 18925 may be identified by casting No. 18905 appearing below No. 1 cylinder location and casting No. 18906 appearing below No. 6 cylinder location.
(Franklin Service News No. 10 also covers this subject.)

FOOTER:

Source: Official FAA Source ↗

Retrieved: Apr 8, 2026

Rights: U.S. Government Public Domain

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