# Performance Class B (CS-23): Airworthiness Requirements

> Certification specifications for Performance Class B aeroplanes (CS-23).

- **Subject:** 032 — Performance
- **Section:** 032-02 — C2-23-Applicable Operational Requirements Performance Class B - Theory
- **Topic code:** 032-02-01
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/performance/c2-23-applicable-operational-requirements-performance-class-b-theory/airworthiness-requirements/

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## Certification Basis (CS-23)

Performance Class B generally covers aeroplanes certified under **CS-23** (Normal, Utility, Aerobatic, Commuter Categories).
*   **Maximum Take-Off Mass (MTOM)**: $\le$ 5,670 kg.
*   **Passenger Seating**: $\le$ 19.
*   **Engines**: Propeller-driven (Single or Multi-engine).

## Key Performance Requirements

Unlike Class A, Class B aeroplanes are **not guaranteed** to maintain performance after an engine failure.

### Stall Speed Limit
For single-engine aeroplanes, the stall speed in the landing configuration ($V_{S0}$) often must not exceed **61 knots** (CAS) to ensure a survivable forced landing speed.

### Climb Requirements (All Engines Operating)
*   Must demonstrate a steady climb gradient at sea level (ISA) of at least:
    *   **4.0%** (Single Engine).
    *   **8.3%** or specific formula (Multi-engine).

### Climb Requirements (One Engine Inoperative)
*   **Single Engine**: No requirement to climb after engine failure.
*   **Twin Engine (Commuter Category)**: Must have a measurable climb gradient at 400 ft above take-off surface.
*   **Twin Engine (Normal/Utility)**: May not have a positive climb gradient at MTOM. If they cannot climb, they must have a determined "negative climb" (drift down) path.

## Equipment
Basic instrumentation is required, but systems redundancy (like dual hydraulic or electrical sources) is less stringent than for Class A.

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