The ability to take off and land vertically, and to hover, makes helicopters useful machines. Unfortunately, because they lack fixed wings to help provide lift, they are also expensive to operate. Helicopters need powerful engines to drive their rotors, and that means they use a lot of fuel. So could they benefit from one of the developments being used to make car engines more efficient-a switch to diesel fuel? eads, Europe's aerospace giant, seems to think they could. One of its subsidiaries, Eurocopter, has begun work on a diesel-powered helicopter.
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