The Sikorsky UH-60 Black Hawk is a four-bladed, twin-engine, medium-lift utility helicopter manufactured by Sikorsky Aircraft. Sikorsky submitted the S-70 design for the United States Army's Utility Tactical Transport Aircraft System (UTTAS) competition in 1972. The Army designated the prototype as the YUH-60A and selected the Black Hawk as the winner of the program in 1976, after a fly-off competition with the Boeing Vertol YUH-61.
The UH-60A entered service with the U.S. Army in 1979, to replace the Bell UH-1 Iroquois as the Army's tactical transport helicopter. This was followed by the fielding of electronic warfare and special operations variants of the Black Hawk. Improved UH-60L and UH-60M utility variants have also been developed. Modified versions have also been developed for the U.S. Navy, Air Force, and Coast Guard. In addition to U.S. Army use, the UH-60 family has been exported to several nations. Black Hawks have served in combat during conflicts in Grenada, Panama, Iraq, Somalia, the Balkans, Afghanistan, and other areas in the Middle East.
http://en.wikipedia.org/wiki/Sikorsky_UH-60_Black_Hawk
A machine gun is a fully automatic mounted or portable firearm, usually designed to fire bullets in quick succession from an ammunition belt or magazine, typically at a rate of several hundred rounds per minute.
Machine guns are generally categorized as submachine guns, machine guns, or autocannons. Submachine guns are hand-held small portable automatic weapons for personal defense or short-range combat firing pistol-caliber rounds. A machine gun is often portable to a certain degree, but is generally used when attached to a mount or fired from the ground on a bipod, and generally fires a rifle cartridge. Light machine guns are small enough to be fired and are hand-held like a rifle, but are more effective when fired from a prone position. The difference between machine guns and autocannons is based on caliber, with autocannons using calibers larger than 16 mm.[1]
Another factor is whether the gun fires conventional rounds or explosive rounds. Guns firing large-caliber explosive rounds are generally considered either autocannons or automatic grenade launchers ("grenade machine guns"). In contrast to submachine guns and autocannons, machine guns (like rifles) tend to share the characteristic of a very high ratio of barrel length to caliber (a long barrel for a small caliber); indeed, a true machine gun is essentially a fully automatic rifle, and often the primary criterion for a machine gun as opposed to an automatic rifle is the presence of a quick-change barrel or other cooling system (see below).
In United States gun law, machine gun is a technical term for any fully automatic firearm, and also for any component or part that will modify an existing firearm such that it functions as a fully automatic firearm.[2]
source: wikipedia
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