Occupant Physical Environment

FAR 23.2320 — Occupant Physical Environment

FAR 23.2320 sets Part 23 design rules for cabin environment: communication, windshield impact, breathable air, pressurization, and oxygen systems.

In Plain English

FAR 23.2320 is a Part 23 airworthiness design standard that tells manufacturers how to protect occupants inside the cabin. While you won't be tested on it like an operating rule, understanding it helps explain why your airplane is built the way it is.

The applicant (manufacturer) must design the airplane to:

Allow clear communication between flightcrew and passengers
Protect the pilot and flight controls from propellers
Protect occupants from serious injury caused by damage to windshields, windows, and canopies

For Level 4 airplanes, the windshield and its supporting structure directly in front of the pilot must withstand a two-pound bird strike at the airplane's maximum approach flap speed without penetration.

The cabin must provide every occupant with air at a breathable pressure, free of hazardous gases, vapors, or smoke — both in normal ops and likely failure scenarios.

If a pressurization system is installed, it must guard against decompression to an unsafe level and against excessive differential pressure. If an oxygen system is installed, it must effectively prevent hypoxia and be free from hazards in its design, operation, or effect on other systems.

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Regulation Text

14 CFR § 23.2320

§ 23.2320 Occupant physical environment. (a) The applicant must design the airplane to— (1) Allow clear communication between the flightcrew and passengers; (2) Protect the pilot and flight controls from propellers; and (3) Protect the occupants from serious injury due to damage to windshields, windows, and canopies. (b) For level 4 airplanes, each windshield and its supporting structure directly in front of the pilot must withstand, without penetration, the impact equivalent to a two-pound bird when the velocity of the airplane is equal to the airplane's maximum approach flap speed. (c) The airplane must provide each occupant with air at a breathable pressure, free of hazardous concentrations of gases, vapors, and smoke during normal operations and likely failures. (d) If a pressurization system is installed in the airplane, it must be designed to protect against— (1) Decompression to an unsafe level; and (2) Excessive differential pressure. (e) If an oxygen system is installed in the airplane, it must— (1) Effectively provide oxygen to each user to prevent the effects of hypoxia; and (2) Be free from hazards in itself, in its method of operation, and its effect upon other components.

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Oral Exam Questions a DPE Might Ask

Q1What does FAR 23.2320 require regarding the windshield on a Level 4 airplane?

Per FAR 23.2320(b), the windshield and supporting structure directly in front of the pilot must withstand, without penetration, the impact of a two-pound bird at the airplane's maximum approach flap speed.

Q2Under FAR 23.2320, what protections must a pressurization system provide if one is installed?

FAR 23.2320(d) requires the pressurization system to be designed to protect against decompression to an unsafe level and against excessive differential pressure.

Q3What does FAR 23.2320 say about cabin air quality for occupants?

FAR 23.2320(c) requires the airplane to provide each occupant with air at a breathable pressure that is free of hazardous concentrations of gases, vapors, and smoke during normal operations and likely failures.

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Occupant protection and survivable emergency-landing conditions

§23.2310 Seaplane & Amphibian Buoyancy

80% excess buoyancy and flotation after likely hull or float flooding

§23.2335 Lightning Protection

Airplane protection from catastrophic lightning effects

§23.2500 Airplane-Level Systems

System safety requirements at the complete-airplane level

§23.2145 Stability