Gravity drop

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Gravity drop refers to the use of gravity to deploy landing gear on an airplane in the event of hydraulic, engine, or power failure. The pilots activate a switch in the cockpit, which releases the lock of the gear door. Gravity then pulls the landing gear outside and deploys it. Once in position the landing gear is ready to use and land on.

One notable use of gravity drop was in the Gimli Glider incident, when a Boeing 767 ran out of fuel, thus losing all hydraulic power.