O texto diz que uma das limitações do helicóptero refere-se

     The ability of a helicopter to hover and land almost anywhere makes it an enormously useful machine. But helicopters have their limitations, particularly when it comes to flying fast. In a recent series of test flights, a new type of chopper has begun smashing speed records.
     The x2 is an experimental helicopter being developed by Sikorsky, an American company, which hopes it will be zipping along at more than 460kph. The company, however, is interested in more than just breaking speed records. It plans to use the technology developed for the x2 in commercial helicopters.
     Sikorsky reckons that future helicopters built using the x2 technology would be extremely versatile machines. They would dash to and from a medical emergency a lot faster. They would also be very agile in flight, which would increase their capabilities in combat.

(Adapted from The Economist September 11, 2010, page 98)