What is MB in Aviation? (Marker Beacon)

Aviation is a fascinating industry with its own set of terminologies and jargon. One such term is the Marker Beacon (MB). If you’ve ever wondered what exactly a Marker Beacon is and how it is used in aviation, this article aims to provide you with a comprehensive understanding. From its definition to its application in the aviation world, we will explore all aspects of the Marker Beacon.

The Basics of Marker Beacons

Before delving into the details of Marker Beacons, it is important to establish a clear understanding of what they are. Marker Beacons are a type of navigation aid used in aviation that provide pilots with crucial information regarding their position during various phases of an instrument approach.

Marker Beacons emit radio signals which are received by aircraft-mounted receivers. These signals aid pilots in identifying specific points along an approach path, helping them maintain a safe and accurate flight trajectory. The term “Marker Beacon” originates from the fact that these beacons mark specific points of interest along the approach path.

The Significance of Marker Beacons in Aviation

Marker Beacons play a crucial role in aviation safety by providing pilots with essential information during instrument approaches. Let’s explore their significance in more detail.

1. Identifying Approach Fixes

During an instrument approach, pilots rely on Marker Beacons to identify approach fixes. These fixes are predetermined points along the approach path that help pilots maintain proper altitude and alignment with the runway. By receiving and interpreting the radio signals emitted by Marker Beacons, pilots can accurately determine their distance from these approach fixes, allowing them to make timely adjustments to their flight path.

2. Providing Distance and Time References

Marker Beacons also provide pilots with distance and time references, aiding them in their decision-making process during an approach. This information helps pilots gauge their progress and plan their actions accordingly. By knowing the specific distances between Marker Beacons, pilots can calculate their groundspeed and estimate their anticipated time of arrival at the runway threshold, enabling them to maintain an efficient and safe approach.

3. Indicating Decision Altitudes

Decision Altitudes (DAs) are critical points during an instrument approach where pilots must make a decision to either continue the approach or execute a missed approach. Marker Beacons play a significant role in indicating Decision Altitudes to pilots. They provide aural and visual indications, such as identifying the presence of the outer, middle, and inner markers, which help pilots determine their altitude above the runway. These markers serve as a valuable reference point, ensuring that pilots make timely decisions during instrument approaches and maintain the highest level of safety.

The Types of Marker Beacons

There are three types of Marker Beacons commonly used in aviation: the Outer Marker (OM), Middle Marker (MM), and Inner Marker (IM). Each beacon serves a specific purpose and assists pilots in different phases of their approach. Let’s take a closer look at each type.

1. Outer Marker (OM)

The Outer Marker is the farthest from the runway among the three types of Marker Beacons. Its purpose is to provide pilots with an early indication of their proximity to the runway. As the outer marker is typically located approximately four to seven miles from the runway threshold, it serves as an initial reference point for pilots to verify their aircraft’s position and adjust their approach accordingly.

2. Middle Marker (MM)

Located closer to the runway than the Outer Marker, the Middle Marker serves as an intermediate point during the approach. Pilots use the Middle Marker to confirm their position, ensuring that they are on the correct glide path and at the correct altitude for a safe landing. When the Middle Marker is activated, pilots are alerted by an aural tone and a visual indicator on their instruments.

3. Inner Marker (IM)

The Inner Marker is the closest Marker Beacon to the runway, generally located approximately 1000 feet before the runway threshold. Its main function is to provide pilots with a final reference point before landing. When the Inner Marker is activated, pilots know that they are approaching the runway threshold and should be preparing to transition from the instrument approach to visual reference for landing.

It is important to note that while these distances may vary depending on the airport and instrument approach procedure, the general purpose and functionality of each Marker Beacon remain consistent across the aviation industry. Pilots rely on these beacons to enhance their situational awareness and ensure a safe approach and landing.


Marker Beacons, abbreviated as MB, are essential navigation aids that assist pilots during instrument approaches. They play a crucial role in identifying approach fixes, providing distance and time references, and indicating decision altitudes. With the three types of Marker Beacons – Outer Marker, Middle Marker, and Inner Marker – pilots can accurately navigate their aircraft and make informed decisions throughout their approach.

Understanding the significance and functionality of Marker Beacons is vital for all aviation enthusiasts and professionals. By familiarizing ourselves with these navigation aids, we contribute to a safer and more efficient aviation industry.

For More: What is NPA in Aviation? (Non-Precision Approach)