Their names are both using the letter X. Which one is Sikorksky X2, others named Eurocopter X3.
Both helicopters are capable of flying faster than ordinary helicopters.
Using the body Eurocopter Dauphin, X3 has several modifications from its predecessor's.
As quoted from the site Physorg, X3 adds an extra engine that is used to drive two extra propellers located on the short wing on either side of its body.
Although only a single additional machine, but the plane is now still at the experimental stage that can run faster than ordinary helicopters.
When the regular heli usually fly between 240-260 km per hour (kph), capable of flying as fast as the X3 430 kph with the stable. This speed puts the X3 to be one of the world's fastest helicopter.
This helicopter is projected to be used for purposes of search and rescue mission search and rescue, coast guard duties, border patrol missions, offshore operations, up to intercity transportation.
As for military purposes, this heli can be used for special forces operations, search and rescue, transporting troops, as well as medical evacuation.
But the X3 is still losing speed by Sikorsky X2 helicopter, which is currently also still in the pilot phase. On trial 15 September 2010, Sikorsky X2 successfully drove at speeds up to 460 kph in stable flight.
Even helicopters can travel 480 kph on a flight at an angle slightly decreased.
Unlike the X3 Eurocopter, Sikorsky X2 coaxial rotor use with dual propellers and reinforced with extra blades in the tail.
This helicopter uses a variety of new technologies, including systems Fly-by-Wire system that lets the engine operate efficiently.
With the speed achieved during the trial, X2 has managed an unofficial record as the world's fastest helicopter.