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 of 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.
Aviation

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.

What is a Ram Air Turbine?

By Paul Scott
Updated: May 23, 2024

A ram air turbine (RAT) is a small airflow driven engine that supplies emergency electrical or hydraulic power to aircraft or, in the case of crop dusters, powers ancillary equipment. These turbines are stowed away behind closed panels during normal flight and are generally only deployed in the case of total loss of power due to multiple engine failures. RATs are standard parts of the redundancy backup systems on larger commercial, military, and many crop dusting aircraft. The average ram air turbine on a passenger aircraft can generate over 50 kilowatts (kW) of power and have a propeller several feet in diameter. Older RAT designs featured twin bladed propellers although newer examples generally have multi-bladed, ducted fans.

Most larger aircraft generate the power needed to run all their systems with generators driven by ancillary gearboxes on the engines or via an auxiliary power unit (APU) while the engines are not running. Should a failure occur during flight where none of these power sources are available, a propeller driven ram air turbine may be deployed to generate power from the air flowing past the aircraft. These small generators are situated behind bays or panels on the fuselage which are remotely operated from the flight deck. Should the need arise, the pilots will deploy the RAT and the bay will open, thus swinging the turbine propeller into the airflow past the aircraft.

In some cases, such as aircraft used in crop dusting operations a ram air turbine is used during normal operation to power chemical spray pumps. This lowers the demand on the aircraft's engine and allows the pump to be located as low on the airframe as possible, thereby making the spray system far simpler and more efficient. The ram air turbine used on these aircraft usually has a fairly small propeller and generates between 500 watts and 5 kilowatts. The RATs on commercial aircraft are obviously far larger with the Airbus A380 ram air turbine measuring five and a quarter feet (1.63 m) across. The average RAT is a little smaller, at approximately 2.6 feet (80 cm) in diameter.

These large commercial ram air turbines are capable of delivering between 25 and 70 kW of peak power to the aircraft systems. This will reduce when the aircraft's speed drops and is a factor which pilots have to contend with during emergency procedures. Older RATs had standard two or four bladed propellers similar in design to those used to drive propeller aircraft. Modern variants have multiblade propellers with shorter, duct enclosed blades which greatly increase efficiency.

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.

Related Articles

Discussion Comments
Share
WikiMotors, in your inbox

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

WikiMotors, in your inbox

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