E6B

The E6B flight computer, nicknamed the "whiz wheel", is a form of circular slide rule used in aviation and one of a very few analog computers in widespread use in the 21st century.

They are mostly used in flight training, because these flight computers have been replaced with electronic planning tools or software and websites that make these calculations for the pilots. These flight computers are used during flight planning (on the ground before takeoff) to aid in calculating fuel burn, wind correction, time en route, and other items. In the air, the flight computer can be used to calculate ground speed, estimated fuel burn and updated estimated time of arrival. The back is designed for wind vector solutions, i.e., determining how much the wind is affecting one's speed and course. See wind triangle and dead reckoning.

They are usually made out of cardboard and plastic, or aluminum and plastic, with lettering and markings either printed or engraved into the metal. Pivots of metal models (metal with plastic grommet) will wear out the plastic grommet prematurely, causing the wheels to spin freely. This is not beneficial when computing while flying. The cardboard models (except when becoming wet) will outlast the metal versions for most people, and will not develop the "free wheel" even after years of use.

Electronic versions are also produced, resembling calculators, rather than manual slide rules. Aviation remains one of the few places that the slide rule still is in widespread use. Manual E6Bs/CRP-1s remain popular with some users and in some environments rather than the electronic ones because they are lighter, smaller, less prone to break, easy to use one-handed, quicker, and do not require electrical power.

In flight training for a private pilot or instrument rating mechanical flight computers are still often used to teach the fundamental computations. This is in part also due to the complex nature of some trigonometric calculations which would be comparably difficult to perform on a conventional scientific calculator. The graphic nature of the flight computer also helps catching many errors which in part explains their continued popularity. The ease of use of electronic calculators means typical flight training literature does not cover the use of calculators or computers at all. In the ground exams for numerous pilot ratings, programmable calculators or calculators containing flight planning software are permitted to be used.

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Wikipedia