Structural Protection

FAR 23.2255 — Structural Protection

FAR 23.2255 requires Part 23 airplanes to protect structure from deterioration, provide ventilation and drainage, and allow access for maintenance.

In Plain English

FAR 23.2255 is a Part 23 airworthiness standard that tells designers of small airplanes how to keep the airframe — down to individual fasteners — durable over the life of the airplane. It has three core requirements:

Protection from deterioration: Every part of the airplane, including small parts like fasteners, must be protected against deterioration or loss of strength from anything likely to happen in the expected operating environment (corrosion, moisture, abrasion, UV, chemicals, temperature, etc.).
Ventilation and drainage: Each part must have adequate provisions for ventilation and drainage, so trapped moisture and contaminants can escape rather than sit and corrode the structure.
Maintainability: For any part needing maintenance, preventive maintenance, or servicing, the design must include a means (access panels, inspection points, removability) to actually accomplish that work.

Why it matters operationally: this is the certification basis behind drain holes you find on wings and fuselages, the corrosion-resistant finishes on hardware, and the access panels you open during preflight or annual inspections. As a pilot, knowing this rule helps you appreciate why keeping drains clear, treating corrosion early, and following the maintenance manual aren't optional — they preserve the protection the airplane was certified with.

Regulation Text

14 CFR § 23.2255

§ 23.2255 Protection of structure. (a) The applicant must protect each part of the airplane, including small parts such as fasteners, against deterioration or loss of strength due to any cause likely to occur in the expected operational environment. (b) Each part of the airplane must have adequate provisions for ventilation and drainage. (c) For each part that requires maintenance, preventive maintenance, or servicing, the applicant must incorporate a means into the airplane design to allow such actions to be accomplished. [Doc. No. FAA-2015-1621, Amdt. 23-64, 81 FR 96689, Dec. 30, 2016, as amended by Doc. No. FAA-2022-1355, Amdt. 23-65, 87 FR 75710, Dec. 9, 2022]

Oral Exam Questions a DPE Might Ask

Q1Under Part 23 certification, what must the designer do to protect the airplane's structure from environmental damage?

Per FAR 23.2255(a), the applicant must protect every part of the airplane, including small parts like fasteners, against deterioration or loss of strength from any cause likely to occur in the expected operational environment.

Q2Why do small airplanes have drain holes in the wings and fuselage — what regulation drives that?

FAR 23.2255(b) requires that each part of the airplane have adequate provisions for ventilation and drainage, which is why drain holes and vent paths are designed into the structure to prevent trapped moisture and corrosion.

Q3How does Part 23 ensure that components needing inspection or servicing can actually be reached?

FAR 23.2255(c) requires the applicant to incorporate a means into the airplane design to allow maintenance, preventive maintenance, or servicing to be accomplished on any part that requires it — typically through access panels and inspection openings.

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