---
title: "CS 25.1027 Propeller feathering system — CS-25 · Avioverse"
description: "(See AMC 25.1027.) (a) If the propeller feathering system depends on engine oil, there must be means to trap an amount of oil in the tank if the supply…"
url: "https://avioverse.aero/regulations/easa/cs-25/subpart-e/cs-25-1027"
---

# CS 25.1027 Propeller feathering system

Large Aeroplanes (CS-25) · CS-25 · EAR revision 26 Jan 2023

IR Implementing rule

## CS 25.1027 Propeller feathering system

(See AMC 25.1027.)

(a) If the propeller feathering system depends on engine oil, there must be means to trap an amount of oil in the tank if the supply becomes depleted due to failure of any part of the lubricating system other than the tank itself.

(b) The amount of trapped oil must be enough to accomplish the feathering operation and must be available only to the feathering pump. (See AMC 25.1027(b).)

(c) The ability of the system to accomplish feathering with the trapped oil must be shown. This may be done on the ground using an auxiliary source of oil for lubricating the engine during operation.

(d) Provision must be made to prevent sludge or other foreign matter from affecting the safe operation of the propeller feathering system.

IR · CS 25.1027 — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMC Acceptable means of compliance

## AMC 25.1027 Inadvertent Propeller Feathering

The design of the propeller feathering system should be such that it is possible to complete the feathering and the unfeathering operation under all normal operating conditions.

AMC · AMC 25.1027 — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMC Acceptable means of compliance

## AMC 25.1027(b) Propeller Feathering

The amount of trapped oil should be sufficient to cover one feathering operation; taking into account the maximum oil leakage in the feathering system due to wear and deterioration in service.

AMC · AMC 25.1027(b) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

[All rules in SUBPART E – POWERPLANT](https://avioverse.aero/regulations/easa/cs-25/subpart-e)

Consolidated from the EASA Easy Access Rules (revision 26 Jan 2023, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.