# AD 49-28-01: Unsatisfactory Spinner

- Type: Airworthiness directive
- Status: Current
- Products: Sierra Hotel Aero Navion (Army L-17A) and Navion A (Army L-17B and L-17C)
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 633 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D2CB6EECE0E1157686256A56006F9191.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/49-28-01

## The airworthiness directive

49-28-01 NAVION: Applies to All Airplanes Equipped With Product Techniques, Inc., Propeller Spinners.

To be accomplished as specified below:

In order to preclude the possibility of continued use of any unsatisfactory spinners which may be in existence, the following steps must be taken:

1. Spinners not previously installed on an aircraft must be inspected before installation for the thickness of the bulkhead. This may be accomplished by measuring the thickness of the bulkhead at the perimeter; measurements should be taken about 1/2 inch from the edge for best accuracy. The manufacturing process used in fabricating the bulkheads reduces the gage of the material about 0.012 inch at the perimeter. Bulkheads measuring less than 0.045 inch at this point must be replaced with heavier gage steel bulkheads.

2. Spinners which have partially completed the inspections previously required by AD 49-01-01 may continue in service until the next 10-hour inspection at which time thebulkhead should be gaged as specified above and replace if under 0.045-inch thickness.

3. Spinners having satisfactorily passed the five inspection periods required by AD 49-01-01 must be inspected for bulkhead thickness, as specified above, within the next 50 hours of flight, and replaced if under 0.045-inch thickness.

It has been determined that bulkheads of 0.058-inch and 0.064-inch cadmium plated steel are satisfactory and do not require the periodic inspections previously specified in AD 49-01-01. However, bulkheads made of thinner gage steel, or of aluminum, are unsatisfactory.

This supersedes AD 49-01-01.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A-782](https://openairdocs.org/tcds/A-782): Sierra Hotel Aero Inc.; names 2 of 8 models: Navion (Army L-17A), Navion A (Army L-17B and L-17C)

## 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: 633 (633 by airframe model, 0 by engine model)
- Makers: Ryan 285, North American 249, Navion 99

Models with the most aircraft:

- [North American NAVION](https://openairdocs.org/model/north-american-navion): 203 aircraft (airframe model)
- [Ryan NAVION](https://openairdocs.org/model/ryan-navion): 170 aircraft (airframe model)
- [Ryan NAVION A](https://openairdocs.org/model/ryan-navion-a): 115 aircraft (airframe model)
- [Navion NAVION A](https://openairdocs.org/model/navion-navion-a): 99 aircraft (airframe model)
- [North American NAVION A](https://openairdocs.org/model/north-american-navion-a): 46 aircraft (airframe model)

All 6 models: https://openairdocs.org/ad/49-28-01/models.md
Every aircraft: https://openairdocs.org/ad/49-28-01/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.