I changed my wall paper recently to this shot of a UPS 767 and today I caught a little detail I hadn’t noticed before.
See that little blur between the main gear? That’s the ram air turbine or RAT. It’s a small turbine that is connected to either a hydraulic pump or electrical generator and is used to generate power.
A RAT on a Boeing 757
RATs are generally only used in an emergency situation where power cannot be provided from the aircraft’s main engines or auxiliary power unit (APU).
Probably the most famous incident involving the use of a RAT was Air Canada Flight 143, commonly referred to as the Gimli Glider. That aircraft, a 767-200, ran out of fuel due to a mathematical error during a flight from Montreal to Edmonton and had to glide its way down from 41,000 feet to make an emergency landing at a former military base. The flight crew successfully used the RAT to provide power to control the aircraft during its descent.
The Gimli Glider post-retirement at Mojave Airport & Spaceport