What is HDG on Boeing 777? (Heading)

The Boeing 777, commonly referred to as the B777, is a wide-body twin-engine airplane manufactured by Boeing Commercial Airplanes. It is one of the most widely used aircraft in the world, serving as both a passenger and a cargo carrier. With its impressive range and advanced technology, the Boeing 777 has revolutionized long-haul flights. In this article, we will explore the heading system on the Boeing 777 and understand its significance in ensuring a safe and efficient flight.

Understanding HDG: The Heading Mode

The heading mode, often abbreviated as HDG, is an integral part of the autopilot system in the Boeing 777. It allows the aircraft to maintain a specific heading or direction during flight. By setting the desired heading, the pilots can ensure that the aircraft stays on course and follows the intended flight plan.

The HDG mode uses various sensors and systems on the aircraft to determine its current heading and make corrections as necessary. One such system is the heading reference system (HRS), which consists of magnetometers that measure the Earth’s magnetic field and provide information about the aircraft’s heading relative to magnetic north. This information is then fed into the autopilot system, allowing it to make adjustments to maintain the desired heading.

In addition to the HRS, the Boeing 777 also utilizes the Attitude and Heading Reference System (AHRS) to provide accurate heading information. The AHRS combines data from multiple sources, including inertial measurement units (IMUs), accelerometers, and gyroscopes, to calculate the aircraft’s orientation and heading. This information is crucial for the HDG mode to function effectively.

During flight, the pilots can engage the HDG mode by selecting it on the autopilot panel. Once engaged, the autopilot system will use the heading information from the HRS or AHRS to maintain the selected heading. If the aircraft deviates from the desired heading, the autopilot will adjust the control surfaces, such as the ailerons and rudder, to bring it back on track.

The HDG mode also works in conjunction with other autopilot modes, such as the lateral navigation (LNAV) mode. When the LNAV mode is engaged, the autopilot will not only maintain the selected heading but also follow the lateral navigation path programmed in the flight management computer (FMC). This integration ensures that the aircraft not only stays on the correct heading but also follows the designated route.

Benefits of the Heading Mode on the Boeing 777

The heading mode plays a crucial role in the safe and efficient operation of the Boeing 777. Here are some of the key benefits it offers:

1. Improved Navigation: By using the HDG mode, pilots can maintain the aircraft’s heading with precision, ensuring that it stays on the planned route. This improves navigation accuracy, especially during long-haul flights where small deviations from the intended path can result in significant changes in fuel consumption and flight time.

2. Enhanced Safety: The HDG mode helps in preventing the aircraft from drifting off course due to factors like wind gusts, turbulence, or minor navigation errors. By automatically making corrections to the heading, the autopilot reduces the workload on the pilots and enhances overall flight safety.

3. Fuel Efficiency: Maintaining the desired heading with precision not only ensures that the aircraft follows the most efficient route but also allows for better fuel planning and optimization. By minimizing deviations from the planned path, the Boeing 777 can save fuel and reduce carbon emissions, contributing to a greener aviation industry.


The heading mode, abbreviated as HDG, is an essential component of the autopilot system on the Boeing 777. It allows pilots to maintain a specific heading during flight, enhancing navigation accuracy, safety, and fuel efficiency. By integrating with other autopilot modes, such as LNAV, the HDG mode ensures that the aircraft not only stays on the correct heading but also follows the programmed lateral navigation path. With its advanced heading system and cutting-edge technology, the Boeing 777 continues to be a reliable and efficient workhorse in the aviation industry.

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