Performance Class A (CS-25): Approach and Landing Theory

032-04-06Pablo Asensio Martínez2026-04-011 min

Climb Requirements

Approach Climb (OEI)

During an approach (one engine inoperative), if a Go-Around is initiated:

  • Configuration: Approach Flaps, Gear Up, OEI, Take-off Thrust.
  • Gradient Requirement:
    • Two Engines: 2.1%.
    • Three Engines: 2.3%.
    • Four Engines: 2.4%.

Landing Climb (AEO)

Also known as "Balked Landing" (Go-Around from very low altitude/touchdown).

  • Configuration: Landing Flaps, Gear Down, AEO, Take-off Thrust.
  • Gradient Requirement: 3.2% (for all aircraft types).
  • This ensures the aircraft can climb away safely even in full landing configuration.

Landing Distance Required (LDR)

The horizontal distance from a screen height of 50 ft to a complete stop.

Operational Factors (Dispatch)

At the planning stage (Dispatch), the aircraft must be able to land within a fraction of the available runway density (LDA).

  • Dry Runway: LDR $\le 60\%$ of LDA (or LDA $\ge 1.67 \times$ LDR).
  • Wet Runway: LDR $\le 60\%$ of LDA, then multiply the required distance by 1.15.
    • Result: LDA $\ge 1.92 \times$ LDR Dry.

In-Flight Calculation

Once in flight, for the actual landing, the "In-Flight" or "Advisory" landing distance is used (often called ALD or OLD). This removes the large 1.67 safety factor but adds a smaller operational margin (e.g., +15%).

Factors Affecting LDR

  • Mass: Higher mass $\rightarrow$ higher $V_{REF}$ $\rightarrow$ longer distance. ($Distance \propto Mass^2$).
  • Altitude: Higher density altitude $\rightarrow$ higher TAS for same IAS $\rightarrow$ longer distance.
  • Wind: Tailwind increases distance significantly.
  • Slope: Downslope increases distance.
  • Surface: Water/Ice/Snow reduces braking action, increasing distance.