Final answer:
A step-down fix is a point where an aircraft must descend to a lower altitude on an instrument approach, necessary for safe descent and obstacle clearance. On the TALLAHASSEE, FL S-LOC RWY 27 approach, these fixes are points on the approach plate where an aircraft must descend to maintain safety and proper approach trajectory.
Step-by-step explanation:
A step-down fix in aviation is a predetermined point where an aircraft descending on an instrument approach, such as the Standard Localizer (S-LOC) approach, must descend to a lower altitude. Step-down fixes are essential for maintaining obstacle clearance and ensuring a safe, staged descent during the final approach.
Using the TALLAHASSEE, FL S-LOC RWY 27 approach as an example, a step-down fix can be identified on the approach plate indicating where the aircraft must descend to a lower altitude before reaching the runway. The approach plate will show a series of altitudes at specific distances from the runway, which the aircraft must not descend below until it reaches the step-down points. The pilot uses this information to safely navigate the approach, avoiding terrain and obstacles, and achieving the correct path to land on Runway 27.