Title: Understanding Airbus A/THR Approach Mode: A Pilot's Detailed Insight
As an airline professional pilot flying Airbus aircraft, it's crucial to have a comprehensive understanding of the Aircraft's Thrust Mode (A/THR) approach behavior, especially during critical phases like descent and landing. Let's delve into the intricacies of A/THR approach mode and how it optimizes aircraft performance below 3,200 feet RA (Radio Altitude).
**Optimized Behavior Below 3,200 ft RA:**
Once the aircraft is below 3,200 feet RA and configured with at least CONF 1 (Configuration 1), the A/THR system undergoes optimization to enhance its responsiveness to speed variations, ensuring smoother control during the descent and approach phase. This optimization is particularly vital as the aircraft transitions to lower altitudes, where precision and stability are paramount.
**Reduced Responsiveness Below 150 ft RA:**
Below 150 feet RA, a specific logic is implemented within the A/THR system to minimize its responsiveness to speed variations. This deliberate adjustment aims to prevent abrupt thrust increases during the latter stages of the approach, which could potentially destabilize the aircraft and lead to an extended flare (the phase where the aircraft's nose is raised just before touchdown).
**Transition to Flare Mode:**
As the aircraft descends further and passes 100 feet RA, a significant transition occurs within the flight mode. The Trimable Horizontal Stabilizer (THS) becomes frozen, and the normal flight mode seamlessly transitions into flare mode in preparation for landing. During this phase, direct stick-to-elevator law is activated, bypassing the auto trim function. This means that the pilot's inputs directly control the elevator without automatic adjustments.
**Flare Mode Characteristics:**
In flare mode, the pilot benefits from full elevator authority, empowering them to precisely control the aircraft's pitch as it descends for landing. However, it's important to note that the flare law does not compensate for ground effect or thrust variations. Instead, it relies on feedback mechanisms such as load factor and pitch rate to provide damping, enhancing control and stability during the critical moments before touchdown.
**Conclusion:**
Understanding the nuances of Airbus A/THR approach mode is essential for every professional pilot operating these advanced aircraft. By comprehending the optimized behavior below 3,200 feet RA, the reduced responsiveness below 150 feet RA, and the transition to flare mode, pilots can effectively utilize the A/THR system to ensure a safe and stable approach and landing, even during challenging conditions. This knowledge underscores the commitment of Airbus to providing cutting-edge technology that enhances flight safety and efficiency.