# Performance Class B (CS-23): Climb, Cruise, and Descent Theory

> En-route performance requirements for Class B aircraft, including single-engine ceilings.

- **Subject:** 032 — Performance
- **Section:** 032-02 — C2-23-Applicable Operational Requirements Performance Class B - Theory
- **Topic code:** 032-02-04
- **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/climb-cruise-and-descent/

---

## En-Route Climb (AEO)

All Class B aircraft must be able to climb to a safe cruising altitude.
*   **Minimum Gradient**: typically **300 ft/min** rate of climb at sea level or a specified gradient at a higher altitude (e.g., 5,000 ft or MSA).

## En-Route (One Engine Inoperative - OEI)

### Single-Engine Aircraft
*   If the engine fails, the aircraft will descend.
*   **Requirement**: The flight must be planned such that, in the event of engine failure, the aircraft can glide to a suitable landing site.
*   **Cloud Ceiling**: Operations on top of clouds are restricted if the pilot cannot descend visually in an emergency.

### Multi-Engine Aircraft
*   Must be able to continue flight or land safely.
*   **Service Ceiling (OEI)**: The altitude where the rate of climb is **50 ft/min**.
*   **Route Requirement**: The aircraft must be able to maintain an altitude above the Minimum Safe Altitude (MSA) along the route, usually 1,000 ft above terrain (2,000 ft in mountainous areas).
*   If the aircraft cannot maintain MSA on one engine, it must obey restrictions similar to single-engine aircraft (visual contact with terrain, proximity to divert fields).

## Descent and Landing

The descent planning must account for:
*   **Wind**: Headwinds increase the descent angle relative to the ground.
*   **Power**: Descent is usually powered to manage engine temperatures (avoiding shock cooling).
*   **Landing Mass**: Must be below the Maximum Structural Landing Mass (MSLM) and the Performance Limited Landing Mass (PLLM) at the destination.

---

Free study notes from pilotsyllabus.com. Not a substitute for training at an approved ATO.