What is FAS in Aviation? (Final Approach Segment)

The final approach segment (FAS), also known as the final approach phase, is a crucial part of aviation procedures that pilots follow when descending toward an airport for landing. It is the final stage before touchdown, where the aircraft aligns with the landing runway, descends to the decision altitude or height, and prepares for landing. The FAS begins at the end of the instrument landing system (ILS) or the glide slope intercept point, which is typically located five miles from the threshold of the runway.

During the final approach segment, the pilot relies on various navigational aids, such as the ILS or a visual approach, to maintain the correct glide path and track the desired course. The FAS is critical for ensuring a safe and stable approach, reducing the risk of accidents and providing a predictable path for the aircraft.

Let’s delve deeper into the components and significance of the final approach segment in aviation.

Components of the Final Approach Segment

The final approach segment consists of several important components that assist pilots in executing a successful landing. These components include:

  • 1. Glideslope or Vertical Path: The glideslope or vertical path is a critical component of the FAS. It provides vertical guidance to the pilot, ensuring the aircraft descends along the correct path towards the runway. The glideslope is typically a 3-degree descent angle, which allows for a controlled descent rate and a smooth touchdown.
  • 2. Lateral Navigation: Lateral navigation refers to the guidance system that directs the aircraft along the correct horizontal track during the final approach. This can be achieved through various means, such as the localizer component of the ILS or the use of waypoints and RNAV (Area Navigation) systems.
  • 3. Decision Altitude or Height: The decision altitude (DA) or decision height (DH) is a predetermined height above the runway at which the pilot must decide to continue the approach or execute a missed approach. It serves as a safety buffer, allowing the pilot to assess the visibility and runway conditions before committing to a landing.
  • 4. Missed Approach Procedure: The missed approach procedure is a predetermined set of actions and maneuvers to be performed by the pilot in the event that landing conditions are deemed unsuitable or unsafe during the final approach segment.
  • 5. Visual Approach: In some cases, particularly during visual meteorological conditions (VMC), pilots may opt for a visual approach instead of relying solely on instrument guidance. A visual approach allows the pilot to maintain visual contact with the runway and obstacles, while still following the recommended approach path.

The combination of these components ensures a stable and controlled approach, enabling pilots to safely navigate their aircraft towards a successful landing.

Significance of the Final Approach Segment

The final approach segment plays a vital role in aviation for several reasons:

  • 1. Precision Landing: With the help of instrument guidance systems like the ILS, the final approach segment allows for precise alignment with the runway, ensuring a safe and accurate landing. This is particularly essential during adverse weather conditions or in low visibility situations.
  • 2. Safety and Avoidance of Obstacles: The final approach segment provides an established flight path that helps pilots navigate around obstacles, such as buildings, hills, or other aircraft. By adhering to the prescribed approach procedures, pilots can minimize the risk of collision or accidents during landing.
  • 3. Consistency and Predictability: Standardized final approach procedures ensure consistency and predictability for pilots, air traffic controllers, and other aviation stakeholders. Following a defined path during the final approach segment reduces confusion and enhances overall safety by providing a clear framework for communication and decision-making.
  • 4. Efficient Air Traffic Management: The final approach segment is a critical phase of flight that contributes to the efficient management of air traffic. By maintaining a predictable flow of arrivals and departures, air traffic controllers can optimize the use of airspace and runway capacity, reducing delays and improving overall operational efficiency.

Understanding the significance of the final approach segment allows pilots and aviation professionals to appreciate its role in ensuring safe, precise, and efficient landing operations.


The final approach segment (FAS) is a critical phase of aviation procedures, where pilots descend toward an airport for landing. It incorporates various components, such as glideslope guidance, lateral navigation, decision altitude, and missed approach procedures, all of which contribute to a safe and controlled approach. The significance of the final approach segment lies in its role in ensuring precision landing, safety, consistency, and efficient air traffic management.

By following the prescribed procedures and utilizing the available navigational aids, pilots can successfully navigate the final approach segment and bring their aircraft safely to the runway. The final approach segment exemplifies the meticulous planning and execution required in aviation to ensure the smooth flow of air traffic and prioritize the safety of passengers and crew members.

For more information and resources on aviation procedures and terminology, visit FAA.gov.

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