What is RAD ALT in Aviation? (Radio Altitude)

When it comes to aviation, there are numerous terms and acronyms that may seem overwhelming to those unfamiliar with the industry. One such term is Radio Altitude, commonly known as Rad Alt. Radio Altitude refers to the altitude above the ground or the height of an aircraft above a certain point, as measured by an onboard radio altimeter. This crucial piece of equipment provides pilots with essential information during takeoff, approach, and landing phases of flight.

Understanding Radio Altitude

Radio Altitude is a significant value for pilots as it differs from barometric altitude, which is measured using atmospheric pressure. The radio altimeter measures the distance between an aircraft and the terrain directly below using radio waves. It accomplishes this by transmitting a radio signal towards the ground and then measuring the time it takes for the signal to return to the aircraft. Based on this time interval, the radio altimeter calculates the height above the ground and provides a precise reading to the pilot.

During various flight phases, pilots rely on the radio altitude to make critical decisions. For example, during takeoff, the radio altitude helps determine the moment the aircraft has left the ground. Similarly, during landing, the radio altitude assists the pilot in making a smooth touchdown by indicating the exact height above the runway. It is vital to note that radio altitude is not affected by barometric pressure changes, making it an accurate measure of a plane’s height above the ground.

The Importance of Radio Altitude

In aviation, precision and accuracy are of utmost importance, and this is where radio altitude plays a crucial role. By providing pilots with real-time information about their height above the ground, it enhances situational awareness and aids in decision-making. Let’s explore the key reasons why radio altitude is vital in aviation:

Safety and Collision Avoidance

In crowded airspace, knowing the exact altitude above the ground is essential for maintaining safe distances between aircraft. By using radio altitude, pilots can adhere to predefined separation standards when flying in close proximity to other aircraft. They can also ensure they remain at a safe altitude when passing over obstacles such as buildings, mountains, or towers. Additionally, during approaches to airports, the radio altitude helps pilots make precise decisions about descending and stabilizing the aircraft for a safe landing.

The radio altitude system also aids in the detection and prevention of potential collisions. When approaching an airport, the radio altitude provides pilots with valuable information to determine whether they are at the correct altitude for a safe landing. If the radio altimeter detects an abnormal descent rate, which could indicate an imminent collision with the ground, it triggers audible warnings, alerting the pilot to take immediate action. This safety feature can be a lifesaver in critical situations.

Precision during Landing

One of the most critical phases of flight is landing, and radio altitude plays a vital role in ensuring a smooth touchdown. The radio altimeter provides pilots with accurate height information as they descend towards the runway. This enables them to gauge the aircraft’s height above the ground more precisely, allowing for adjustments in the rate of descent and potentially avoiding a hard landing.

During poor weather conditions such as fog, low visibility, or darkness, the radio altimeter becomes even more crucial. It assists pilots in maintaining the correct glide path and descent rate, ensuring they stay on track for a safe landing. By relying on the radio altitude, pilots can maintain a stabilized approach and minimize the chances of runway contact before the designated touchdown point.

Enhanced Helicopter Operations

Radio altitude holds particular significance for helicopter operations, as these aircraft often fly at much lower altitudes than fixed-wing planes. Helicopters frequently perform operations such as low-level flights, hovering, and landing in confined spaces. The radio altimeter provides pilots with accurate information about their height above the ground during these maneuvers, ensuring safe and precise operations.

Furthermore, the radio altimeter assists pilots in certain specialized operations, such as hover taxiing and hovering above water or other surfaces. In these scenarios, maintaining a specific height above the ground is crucial, and radio altitude provides the necessary data to execute these maneuvers with precision.


Radio altitude, or Rad Alt, is a fundamental component of aviation that provides pilots with accurate information about their height above the ground. This measurement system enhances safety, assists in collision avoidance, and ensures precision during critical flight phases such as takeoff, approach, and landing. Whether it’s maintaining safe distances between aircraft, executing precise landings, or conducting specialized operations, radio altitude plays a vital role in the success and safety of aviation.

For More: What is ATSAW in Aviation? (Airborne Traffic Situational Awareness)