What is B/C on Boeing 737? (Back Course)

When it comes to aviation, there are numerous terminologies and phrases that can seem confusing to those who are not familiar with the industry. One such term is “Back Course” or B/C, which is often mentioned in relation to the Boeing 737 aircraft. Let’s explore what Back Course means in the context of the Boeing 737 and how it is relevant in navigation and instrument approaches.

The Function and Significance of Back Course

Back Course, in simple terms, refers to an approach to a runway from the opposite direction of normal. Normally, aircraft approach a runway in the same direction as the runway’s orientation, with the runway threshold to the pilot’s left or right. However, certain airfields and runways have specific circumstances where a Back Course approach is necessary.

Why would an aircraft need to perform a Back Course approach? One common reason is when the primary approach is being modified or undergoing maintenance. In such cases, the Back Course can provide an alternate approach path to the runway. It allows aircraft to safely land and take off, even when the usual approach path is unavailable. Back Course approaches are especially important during runway maintenance to ensure minimal disruption to airport operations.

In addition to runway maintenance, Back Course approaches can also be used as a backup option during certain weather conditions. For example, during strong crosswinds, it may be safer for an aircraft to approach the runway from the opposite direction, where the wind is less of a factor. This allows for safer landings and takeoffs in challenging weather conditions.

Back Course Navigation and Instrument Approaches

Now that we understand the purpose of Back Course approaches, let’s delve into the navigation and instrument approach procedures involved in executing them on the Boeing 737.

The Boeing 737, like many modern aircraft, utilizes a variety of navigation aids to accurately navigate and execute instrument approaches. One such aid is the Instrument Landing System (ILS), which provides precise guidance to the runway during both normal and Back Course approaches.

During a Back Course approach, the pilot selects the Back Course mode on the Flight Management Computer (FMC) or Flight Management System (FMS). The FMC/FMS then generates the appropriate flight path and displays it on the aircraft’s Primary Flight Display (PFD) and Navigation Display (ND). This allows the pilot to follow a predetermined course aligned with the runway, ensuring a safe approach and landing.

The ILS used during Back Course approaches consists of two main components: the Localizer and the Glide Slope. The Localizer provides lateral guidance, ensuring that the aircraft is properly aligned with the runway. The Glide Slope, on the other hand, provides vertical guidance, allowing the pilot to maintain the correct descent path towards the runway.

During a Back Course approach, the Localizer and Glide Slope signals are reversed compared to a normal approach. Instead of flying towards the Localizer to align with the runway, the pilot flies away from it but maintains the same lateral track. The Glide Slope, instead of guiding the aircraft on an upward descent, guides it downwards towards the runway. These reversed signals help the aircraft navigate and align with the runway threshold even when approaching from the opposite direction.


Understanding the concept of Back Course is essential for pilots operating the Boeing 737 and for those interested in aviation. Back Course approaches serve as vital alternatives to traditional approaches, allowing aircraft to land and take off when conventional methods are unavailable or unsuitable. The use of navigation aids, such as the Instrument Landing System, helps pilots safely navigate Back Course approaches and maintain precise alignment with the runway. By incorporating Back Course procedures and approaches into their training, pilots can enhance their aviation knowledge and skill set, contributing to safer and more efficient operations.

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