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

032-02-04Pablo Asensio Martínez2026-04-011 min

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.