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).

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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