14 CFR § 25.393 - Loads parallel to hinge line.

---
identifier: "/us/cfr/t14/s25.393"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "14 CFR § 25.393 - Loads parallel to hinge line."
title_number: 14
title_name: "Aeronautics and Space"
section_number: "25.393"
section_name: "Loads parallel to hinge line."
chapter_name: "FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "C"
subchapter_name: "AIRCRAFT"
part_number: "25"
part_name: "AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "49 U.S.C. 106(f), 106(g), 40113, 44701, 44702 and 44704; Pub. L. 115-254, 132 Stat 3281 (49 U.S.C. 44903 note)."
regulatory_source: "Docket No. 5066, 29 FR 18291, Dec. 24, 1964, unless otherwise noted."
cfr_part: "25"
---


# 25.393 Loads parallel to hinge line.

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

(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.