We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is a Ground Proximity Warning System?

By John Markley
Updated May 23, 2024
Our promise to you
WikiMotors is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WikiMotors, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A ground proximity warning system, or GPWS, is a type of equipment carried by airplanes to warn pilots if they are at a dangerously low altitude and in danger of crashing. The main purpose of these systems is to prevent what is called a controlled flight into terrain crash, or CFIT, an accident in which an aircraft crashes into the ground, the water, or an obstacle such as a mountain or building despite being properly crewed and airworthy. This can be the result of factors such as navigation errors, pilot fatigue or disorientation, or reduced visibility owing to weather conditions. CFIT incidents have become dramatically less frequent since ground proximity warning systems entered widespread use in the 1970s. The use of a GPWS in large aircraft is required by law in many countries.

The aircraft's altitude is monitored by a ground proximity warning system with a radar altimeter, which transmits radio waves downward from the plane to determine how far away the ground is. Most radar altimeters carried by commercial aircraft are short-range devices with ranges of less than a mile (about 1.6 km). The information from the radar is monitored and analyzed by a computer that can identify hazardous situations and trends in the data, such as a dangerously rapid rate of descent, dangerously close ground during, or unexpected loss of altitude. If hazardous conditions are detected, the ground proximity warning system gives visual and audio warning signals to the pilot.

The primary limitation of standard ground proximity warning system designs is that it looks only directly below the aircraft. It can detect when the airplane is too low or losing altitude, but if the terrain itself rises steeply, the GPWS won't be able to inform the pilot until the aircraft is already over the rising terrain. Such a warning may come too late, especially if darkness or weather conditions have obscured the ground. In civilian aircraft, this weakness was addressed by the development of the enhanced ground proximity warning system (EGPWS), an advance made possible by the creation of the global positioning system (GPS). The EGPWS contains an electronic terrain database and maintains constant contact with the GPS to track the aircraft's own location, allowing it to provide pilots with accurate data on terrain beyond the range of its own radar.

The limitations of a conventional GPWS become a far graver problem in a high-speed military aircraft flying at low altitudes. If such an aircraft is approaching terrain that presents a collision hazard, such as a hill or mountain, any warning of the aircraft's distance from the ground that doesn't come until the plane is actually over the rising slope will arrive mere fractions of a second before collision. Thus, some modern military aircraft, such as the the American F-16 Fighting Falcon, the French Mirage 2000, and the Eurofighter Typhoon, are equipped with a more sophisticated array of equipment that combines the radar altimeter, digital terrain maps, and GPS link used in an EPGWS, with additional data from the aircraft's flight control and inertial navigation systems. This allows the aircraft to project its current flight path miles ahead and check it against its elevation maps to give the pilot more advanced warning of possible collisions.

WikiMotors is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

By anon249108 — On Feb 20, 2012

Nice article. It was very helpful. I learned a lot about flight safety/collision prevention and this article also triggered my thoughts about a few aspects of human behavior which can be compared with ground proximity warning system. Thanks for the article.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.