# AD 48-50-01: Cylinder Base Flange

- Type: Airworthiness directive
- Status: Current
- Products: Wytwornia Sprzetu Komunikacyjnego 6A4-150-B3 and 6A4-150-B31
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Registered aircraft: 623 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/BC648FB6AADECCCC8625682B006138B3.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/48-50-01

## The airworthiness directive

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.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E-238](https://openairdocs.org/tcds/E-238): Franklin Sp. z.o.o.; names 2 of 7 models: 6A4-150-B3, 6A4-150-B31

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 623 (0 by airframe model, 623 by engine model)
- Makers: Stinson 479, Bellanca 102, Universal Stinson 36, Cessna 1, Consolidatedvultee Acft 1, Fletcher 1, Groelz 1, Interstate 1, Stits Playboy 1

Models with the most aircraft:

- [Franklin 6A4150 series](https://openairdocs.org/engine/franklin-6a4150-series): 623 aircraft (engine model)

All 1 models: https://openairdocs.org/ad/48-50-01/models.md
Every aircraft: https://openairdocs.org/ad/48-50-01/aircraft.md

Its text cites no advisory circulars or STCs.

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