# AD 56-17-03: Valve Tube

- Type: Airworthiness directive
- Status: Current
- Products: Hartzell Propeller HC-12X20-1, HC-12X20-2, HC-12X20-3, HC-12X20-4, HC-12X20-5, HC-12X20-6, HC-12X20-7, HC-12X20-8 and HC-12X20-9
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/B0FAD8F97356F6EB86256965004AF22A.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/56-17-03

## The airworthiness directive

56-17-03 HARTZELL: Applies to All Model HC-12X20 Reversing Propellers Installed on Downer (Republic) RC-3 Aircraft Having B-55 Valve Assembly.

Compliance required as soon as possible but not later than next 25 hours of operation and each 100 hours flight time thereafter.

There have been two reported instances of broken valve tube A-57. These failures were due to vibration of the valve assembly and the weakening effect of the valve porthole. Failure of this part will allow the propeller to go into reverse under certain conditions, forcing the airplane to land. In view of the possible serious consequences resulting from inadvertent reversal of the propeller, disassemble the valve and inspect the A-57 valve tube around the valve port with a magnifying glass or with magnetic inspection equipment. If no cracks are found, the sharp edges at the sides of the porthole should be rounded slightly, using a fine round file.

This inspection is not required for valve assembly B-299.

(Hartzell Service Bulletin No. 38 dated June 16, 1956, covers the same subject.)

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS P-845](https://openairdocs.org/tcds/P-845): Hartzell Propeller Inc.; names 9 of 9 models: HC-12X20-7, HC-12X20-5, HC-12X20-6, HC-12X20-4, HC-12X20-9, HC-12X20-3, HC-12X20-2, HC-12X20-1…

## Registered aircraft it may apply to (OpenAirDocs)

No registered aircraft matched the models it names.

Its text cites no advisory circulars or STCs.

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