Final answer:
Rain on final approach can create visual illusions, making the pilot perceive they are higher and further away, potentially causing an undershoot of the runway. Maintaining focus on flight instrumentation and approach slope indicators is critical for a safe landing.
Step-by-step explanation:
When it is raining on final approach, it can cause the illusion of being higher and further away from the runway, causing the tendency to undershoot the approach. The visual distortions are caused by the rain altering the pilot's perception of the approach path. Especially, when pilots are flying visually, the rain reduces visibility and can distort how the runway lights and environment appear. During an instrument approach, relying on flight instruments is crucial to maintaining the correct glide path. However, for visual approaches in rain, careful attention must be paid to approach slope indicators such as PAPI or VASI, and maintaining extra vigilance is key to ensure a safe landing.