48-50-01: Cylinder Base Flange
FAA order 48-50-01 is an airworthiness directive. The FAA's subject line: Cylinder Base Flange. System: engine.
What it applies to as the FAA lists it
- Kind of product
- Engine
- Makes
- Wytwornia Sprzetu Komunikacyjnego
- Models
- 6A4-150-B3, 6A4-150-B31
Dates and paperwork
- Docket
- Unknown
- Status
- Current
- The FAA's document
- Read the order on the FAA's site
The order itself the regulatory text, as published
Show the full text (1,014 characters)
48-50-01 FRANKLIN: Applies to All Bellanca 14-13, 14-13-2 and Universal (Stinson) 108, 108-1 Aircraft Equipped With Franklin Model 6A4-150-B3 and B31 Engines With Serial Numbers 11000 to 14000 Inclusive.
Compliance required after each 25 hours of operation.
To prevent possible cylinder base flange failure, visual inspection for cracks just above the base flange should be made every 25 hours of operation on the early type cylinders until replaced by the later type cylinders. Early type cylinders have a flat section which extends 3/8 inch to 7/8 inch from the outer edge of the base flange. On later type cylinders the flat section has been practically eliminated by extending the ribbed section close to the edge of the flange.
It is urgently recommended that early type cylinders be replaced at the earliest opportunity.
(Franklin Service Bulletin No. 69 covers this same subject and offers special discounts effective through January 1949, for cylinder replacements).
This supersedes AD 48-47-02.
Source: FAA Dynamic Regulatory System, airworthiness directives. The FAA's document is the authority; the register counts are this site's, from the FAA register of November 6, 2026. Connections as data: /graph/directive/48-50-01.json · aircraft systems.