# Performance Class A (CS-25): Take-off Theory

> Detailed analysis of take-off speeds, distances, and engine failure scenarios for Class A aircraft.

- **Subject:** 032 — Performance
- **Section:** 032-04 — CS-25-Applicable Operational Requirements Performance Class A – Theory
- **Topic code:** 032-04-01
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/performance/cs-25-applicable-operational-requirements-performance-class-a-theory/take-off/

---

## Key Speeds

Class A performance is defined by critical speeds:
*   **$V_1$ (Decision Speed)**: The maximum speed at which the pilot must take the first action to stop the aircraft within the accelerate-stop distance. It is also the minimum speed at which the aircraft can continue the take-off following an engine failure.
*   **$V_R$ (Rotation Speed)**: The speed at which rotation is initiated. $V_R \ge V_1$.
*   **$V_2$ (Take-off Safety Speed)**: The target speed to be reached at the screen height (35 ft) with one engine inoperative. It ensures climb performance and controllability.
*   **$V_{MCG}$ (Min Controllability Speed Ground)**: Minimum speed to maintain directional control on the ground using only aerodynamic controls (rudder) after an engine failure. $V_1 \ge V_{MCG}$.
*   **$V_{MCA}$ (Min Controllability Speed Air)**: Minimum speed to maintain directional control in the air. $V_2 \ge 1.1 V_{MCA}$.

## Distances Required

![Declared Distances Diagram](https://upload.wikimedia.org/wikipedia/commons/0/04/Aim_fig_4-3-5_Declared_Distances_with_Full-Standard_Runway_Safety_Areas%2C_Runway_Object_Free_areas%2C_and_Runway_Protection_Zones.jpg)

### Take-Off Distance Required (TODR)
The horizontal distance from brake release to the point where the aircraft reaches a screen height of **35 ft**.
*   **Condition**: The longer of:
    1.  **OEI (One Engine Inoperative)**: Distance with critical engine failure at $V_{EF}$ (just before $V_1$).
    2.  **AEO (All Engines Operating)**: Distance with all engines operating $\times 1.15$.

### Accelerate-Stop Distance Required (ASDR)
The distance to accelerate to $V_1$, experience an engine failure, recognize it (1 second), and bring the aircraft to a complete stop.
*   **Condition**: The longer of:
    1.  **OEI**: Stop with one engine failed and reverse thrust (if credited, usually not on dry runway).
    2.  **AEO**: Stop with all engines operating (Rejected Take-off for other reasons).

### Take-Off Run Required (TORR)
The distance to accelerate to lift-off plus a portion of the airborne distance up to the screen height.
*   Relevant when the runway has a **Clearway** (area beyond the runway free of obstacles).
*   **OEI**: Run to midpoint between LOF (Lift Off) and 35 ft.
*   **AEO**: Run to midpoint between LOF and 35 ft $\times 1.15$.

## Balanced Field Length
A condition where **TODR = ASDR**.
*   This occurs at a specific $V_1$ value.
*   If $V_1$ is lower, ASDR is shorter but TODR is longer.
*   If $V_1$ is higher, TODR is shorter but ASDR is longer.
*   Balanced Field Length is the minimum field length required for a given weight if $V_1$ is optimized.

---

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