Performance values assume the threshold crossing occurs at how many feet?

Performance values assume the threshold crossing occurs at how many feet?

• A. 40 ft
• B. 50 ft
• C. 60 ft
• D. 70 ft

Answer: (B)

Performance values assume the threshold crossing occurs at fifty feet above the runway. This standard reference point gives a consistent basis for calculating landing and takeoff performance, such as the required landing distance and the energy to be dissipated on touchdown. Crossing at this height provides a realistic balance between having enough flare and clearance and not overestimating or underestimating the aircraft’s energy state at the threshold. Using a lower height would imply less energy to dissipate and underestimate required distance, while a higher height would overestimate it and lead to unnecessarily conservative results. Fifty feet is the standard assumption for these calculations.

Performance values assume the threshold crossing occurs at fifty feet above the runway. This standard reference point gives a consistent basis for calculating landing and takeoff performance, such as the required landing distance and the energy to be dissipated on touchdown. Crossing at this height provides a realistic balance between having enough flare and clearance and not overestimating or underestimating the aircraft’s energy state at the threshold. Using a lower height would imply less energy to dissipate and underestimate required distance, while a higher height would overestimate it and lead to unnecessarily conservative results. Fifty feet is the standard assumption for these calculations.