14 CFR § 27.1435 - Hydraulic systems.

---
identifier: "/us/cfr/t14/s27.1435"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "14 CFR § 27.1435 - Hydraulic systems."
title_number: 14
title_name: "Aeronautics and Space"
section_number: "27.1435"
section_name: "Hydraulic systems."
chapter_name: "FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "C"
subchapter_name: "AIRCRAFT"
part_number: "27"
part_name: "AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT"
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, 44704."
regulatory_source: "Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted."
cfr_part: "27"
---


# 27.1435 Hydraulic systems.

(a) *Design.* Each hydraulic system and its elements must withstand, without yielding, any structural loads expected in addition to hydraulic loads.

(b) *Tests.* Each system must be substantiated by proof pressure tests. When proof tested, no part of any system may fail, malfunction, or experience a permanent set. The proof load of each system must be at least 1.5 times the maximum operating pressure of that system.

(c) *Accumulators.* No hydraulic accumulator or pressurized reservoir may be installed on the engine side of any firewall unless it is an integral part of an engine.