When is the normal law flight mode active?

Normal law flight mode is an important operational mode for the A320's fly-by-wire system, designed to enhance flight safety and performance during critical phases of flight. The correct answer specifies that normal law is active from liftoff until the flare mode engages during landing at 50 feet radio altitude (RA).

This period encompasses the aircraft's ascent after taking off and the approach phase leading up to landing. During this time, the aircraft's flight control laws prioritize safety and handling characteristics, allowing for maximum control and stability. This mode encompasses various flight parameters that regulate the aircraft’s performance, such as load factor protection, bank angle protection, and pitch limits, which are crucial for normal flight operations.

As the aircraft approaches landing, normal law remains active until the aircraft is about to transition into flare mode, which is essentially the phase just before touchdown where the pilots reduce the descent rate and prepare for landing on the runway. Thus, the definition and extent of normal law’s operation aligns perfectly with option B.

The other options either extend the active phase of normal law unnecessarily, such as suggesting it operates from engine start to shutdown or throughout the entire flight without recognizing the transition to landing phases, or they misrepresent the engagement parameters related to the flare.