Accelerate-Go Distance
Understanding accelerate-go distance is crucial for ensuring that, even in the event of an engine failure at the most critical moment, there is enough runway to safely continue the takeoff. This knowledge underpins safe decision-making and compliance with performance regulations.
Accelerate-go distance is the runway length required for an aircraft to accelerate from standstill, experience a critical engine failure at VEF (usually close to V1), and then continue the takeoff with one engine inoperative, reaching the required screen height. This distance is vital for determining safe takeoff performance, especially for multi-engine aircraft, and directly influences runway length requirements and operational limits.
Quick Check
What does the accelerate-go distance represent in takeoff performance calculations?
Go beyond the textbook.
Explanation
What is Accelerate-Go Distance?
Accelerate-go distance, sometimes called takeoff accelerate-go or accelerate-go performance, is the total runway length needed for an aircraft to accelerate to the engine failure speed (VEF), lose one engine, and then continue the takeoff, reaching the regulatory screen height (typically 35 ft for jets, 50 ft for props) on the remaining engines. This scenario assumes the engine failure occurs at the worst possible moment for continued takeoff.
How is Accelerate-Go Distance Determined?
- The calculation starts with all engines operating from brake release.
- At VEF, a critical engine fails. The pilot continues the takeoff using only the remaining engines.
- The aircraft must reach the screen height at or above V2 (takeoff safety speed).
- The distance includes the ground roll to VEF, transition after engine failure, and the climb to screen height.
Accelerate-Go vs Accelerate-Stop
- Accelerate-go distance is compared with accelerate-stop distance (the distance to abort the takeoff and stop safely after an engine failure at VEF).
- The longer of the two distances determines the minimum required runway length for safe operations.
- A balanced field occurs when both distances are equal.
Factors Affecting Accelerate-Go Distance
- Aircraft mass: Higher mass increases the required distance.
- Runway slope and wind: Uphill slopes and tailwinds increase the distance, while downhill slopes and headwinds reduce it.
- Runway surface: Wet or contaminated runways can increase the accelerate-go distance due to reduced acceleration.
- Aircraft configuration: Flap settings, anti-ice, and other configuration changes affect performance.
Operational Use
- Pilots use accelerate-go distance to ensure the available runway is sufficient for a safe takeoff with an engine failure.
- Performance charts and tables in the AFM or provided by the operator are used to determine the required runway length for given conditions.
Exam Emphasis
- Expect questions on the definition, calculation, and comparison with accelerate-stop distance.
- Be able to interpret performance charts and understand how various factors affect accelerate-go distance.
Key Points
Exam Traps & Typical Mistakes
Example Exam Questions
Which factor increases the accelerate-go distance for a given aircraft?
How does accelerate-go distance compare to accelerate-stop distance on a balanced field?
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