# AD 47-21-05: Propeller Control Friction Lock

- Type: Airworthiness directive
- Status: Current
- Products: Sierra Hotel Aero Navion (Army L-17A)
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 373 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/4FD20F470740278386256A56006E11F2.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/47-21-05

## The airworthiness directive

47-21-05 NAVION: (Was Mandatory Note 4 of AD-782-3.) Applies to Serial Numbers NAV-4-11 Through 21 and 44 Through 47.

To be accomplished not later than August 1, 1947.

Replace the original propeller control with one that incorporates a positive friction lock in accordance with NAA Kit Drawing 145-89011.

(NAA Field Service Bulletin No. 5 covers this change.)

## 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 1 of 8 models: Navion (Army L-17A)

## 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: 373 (373 by airframe model, 0 by engine model)
- Makers: North American 203, Ryan 170

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)

All 3 models: https://openairdocs.org/ad/47-21-05/models.md
Every aircraft: https://openairdocs.org/ad/47-21-05/aircraft.md

Its text cites no advisory circulars or STCs.

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