What is EHSI in Aviation? (Electronic Horizontal Situation Indicator)

Aviation is a complex field that relies heavily on technology to keep flights safe and efficient. One important piece of equipment used in aircraft navigation is the Electronic Horizontal Situation Indicator, also known as the EHSI. This device provides pilots with crucial information about their position, heading, and flight path, allowing them to navigate accurately and minimize the risk of accidents. In this article, we will explore the features and functions of the Electronic Horizontal Situation Indicator, and understand its significance in aviation.

The Role of the Electronic Horizontal Situation Indicator

The Electronic Horizontal Situation Indicator, abbreviated as EHSI, is a primary navigation instrument used in modern aircraft. It displays the aircraft’s position and heading on a horizontal plane, providing pilots with essential information for situational awareness. The EHSI combines data from various onboard systems, such as the Inertial Navigation System (INS), Global Positioning System (GPS), and the aircraft’s Flight Management System (FMS), to present an accurate and real-time representation of the aircraft’s position.

Features and Functionality of the EHSI

The Electronic Horizontal Situation Indicator offers a range of features that aid pilots in navigation and flight management. Let’s explore some of the key functionalities of the EHSI:

1. Display Modes

The EHSI offers multiple display modes, allowing pilots to customize the information they receive based on their preferences and the phase of flight. The most commonly used display modes are:

  • Map Mode: This mode provides a top-down view of the aircraft’s position, similar to a map. It displays the aircraft’s current position, planned route, waypoints, and ground references. Pilots can also zoom in and out to get a better understanding of their surroundings.
  • Plan Mode: In this mode, pilots can view their flight plan in detail. It displays the various waypoints, airways, and altitude restrictions along the planned route.
  • Nav Mode: The Nav mode focuses on the aircraft’s immediate navigation. It shows the aircraft’s heading, bearing to the next waypoint, groundspeed, and distance to the next waypoint.
  • VOR Mode: This mode is specifically designed for VHF Omnidirectional Range (VOR) navigation. It displays the selected VOR station, its radial, and any deviations from the desired course.

2. Integrated Data Sources

The EHSI integrates data from various onboard systems to provide accurate and up-to-date information. It receives inputs from the aircraft’s navigation sensors, such as the GPS and INS, to determine the aircraft’s position and heading. Additionally, it interfaces with the Flight Management System (FMS) to obtain flight plan data and waypoints. By consolidating information from different sources, the EHSI ensures that pilots have a comprehensive understanding of their flight conditions.

3. Warning and Alert Systems

The Electronic Horizontal Situation Indicator incorporates warning and alert systems to enhance flight safety. It provides visual and audible alerts to pilots in case of any deviations from the planned route, altitude restrictions, or potential conflicts with other aircraft. These alerts enable pilots to take immediate corrective actions, reducing the risk of accidents and ensuring a smooth and safe flight.


The Electronic Horizontal Situation Indicator plays a vital role in aviation, providing pilots with accurate and real-time information about their position, heading, and flight path. Its various display modes, integrated data sources, and warning systems contribute to improved situational awareness and safer flying. As technology continues to advance, the EHSI will likely undergo further enhancements, making it an indispensable tool for pilots in the ever-evolving world of aviation.

For More: What is FIKI in Aviation? (Flight Into Known Icing)