What is RA on Boeing 737? (Radio Altitude)

The Boeing 737 is one of the most popular and widely used commercial aircraft models in the world. It has undergone numerous upgrades and improvements over the years to enhance its performance, safety, and efficiency. One of the crucial instruments in the cockpit of a Boeing 737 is the Radio Altitude (RA) system. In this article, we will explore what Radio Altitude is, its importance, and how it functions within the context of the Boeing 737.

The Role of Radio Altitude on Boeing 737

The Radio Altitude system on the Boeing 737 is a critical tool that provides accurate altitude information to the pilot and other flight systems. It measures the vertical distance between the aircraft’s altitude above the terrain or an obstacle by using radio waves. This information is crucial during takeoff, approach, and landing phases of the flight.

The Radio Altitude system aids in determining the aircraft’s height above the ground, particularly during low visibility conditions such as fog, snow, or heavy rain. It allows the pilot to make informed decisions, maintain proper clearance from the ground, and ensure a safe approach and landing.

Radio Altitude is displayed to the pilot through the Radio Altimeter Indicator, which is usually located on the primary flight display or the instrument panel. The indicator displays the altitude in feet or meters and provides a visual reference for the pilot.

How Does the Radio Altitude System Work?

The Radio Altitude system on the Boeing 737 works by sending and receiving radio waves. It consists of a radio altimeter antenna located on the fuselage underside. This antenna emits radio frequency waves towards the ground and measures the time it takes for the waves to travel from the aircraft to the ground and back.

The system then calculates the altitude based on the duration of the round trip of the radio waves. By using the speed of light as a constant, the time difference between transmission and reception is converted into altitude, which is then displayed on the Radio Altimeter Indicator.

The accuracy of the Radio Altitude system is vital for the safe operation of the aircraft. It must account for factors such as speed, temperature, and atmospheric conditions to provide precise altitude measurements. The system is also calibrated regularly to ensure optimal accuracy and reliability.

Advantages of the Radio Altitude System

The Radio Altitude system brings several advantages to the Boeing 737 and its flight operations. Here are some key benefits:

  • Enhanced Safety: The Radio Altitude system provides crucial information to the pilot during low visibility conditions, enabling them to maintain a safe distance from the ground and avoid potential obstacles.
  • Improved Landing Precision: By accurately measuring the aircraft’s height above the ground, the system assists the pilot in executing precise landings, especially in challenging environments or on short runways.
  • Increased Situational Awareness: The Radio Altitude system enhances the pilot’s situational awareness by providing a real-time display of the aircraft’s altitude above the ground, even when visibility is poor.


The Radio Altitude system plays a critical role in ensuring the safety, performance, and efficiency of the Boeing 737 aircraft. By providing accurate altitude information, it enables pilots to make informed decisions during critical phases of flight. The system’s ability to measure the aircraft’s height above the ground accurately is especially valuable during low visibility conditions. Overall, the Radio Altitude system enhances the pilot’s situational awareness and contributes significantly to the safe operation of the aircraft.

For more information about the Boeing 737 and its systems, you can refer to the official Boeing website here.

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