What is the critical parameter for airspeed at 1,000ft HAT during approach?

The critical parameter for airspeed at 1,000 feet Height Above Terrain (HAT) during approach is to maintain an airspeed that is within +15/-5 knots of the approach speed (denoted as Vap). This range ensures a safe and stable approach while allowing for slight variations in airspeed that may occur due to environmental factors, changes in aircraft configuration, or pilot inputs.

Maintaining the airspeed within this controlled range is essential for ensuring the aircraft's performance during the approach phase, as it directly affects the lift and aircraft handling characteristics. If the airspeed is too low, it could lead to a stall, while being too high may lead to difficulties in controlling the descent rate or managing landing configurations.

Having an accurate airspeed allows the pilot to make informed decisions and adjust for any needed corrections, fostering a smoother and safer approach to landing. The defined parameters serve as guidelines to enhance safety and optimize aircraft performance during this critical phase of flight.