---
title: "CS 25.393 Loads parallel to hinge line — CS-25 · Avioverse"
description: "(See AMC 25.393) (a) Control surfaces and supporting hinge brackets must be designed for inertia loads acting parallel to the hinge line."
url: "https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-393"
---

# CS 25.393 Loads parallel to hinge line

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

IR Implementing rule

## CS 25.393 Loads parallel to hinge line

(See AMC 25.393)

(a) Control surfaces and supporting hinge brackets must be designed for inertia loads acting parallel to the hinge line. (See AMC 25.393(a).)

(b) In the absence of more rational data, the inertia loads may be assumed to be equal to KW, where –

(1) K = 24 for vertical surfaces;

(2) K = 12 for horizontal surfaces; and

(3) W = weight of the movable surfaces.

\[Amdt 25/18]

IR · CS 25.393 — CS-25 · ED Decision 2016/010/R · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMC Acceptable means of compliance

## AMC 25.393(a) Loads parallel to hinge line

The loads parallel to the hinge line on primary control surfaces and other movable surfaces, such as tabs, spoilers, speedbrakes, flaps, slats and all-moving tailplanes, should take account of axial play between the surface and its supporting structure in complying with CS 25.393(a). For the rational analysis, the critical airframe acceleration time history in the direction of the hinge line from all flight and ground design conditions (except the emergency landing conditions of CS 25.561) should be considered. The play assumed in the control surface supporting structure, should include the maximum tolerable nominal play and the effects of wear.

AMC · AMC 25.393(a) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

[All rules in SUBPART C – STRUCTURE](https://avioverse.aero/regulations/easa/cs-25/subpart-c)

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.