LYCOS RETRIEVER 
Helicopter: Helicopters
built 660 days ago
The helicopter was put to military use almost immediately after its introduction. While it was not utilized extensively during World War II, the jungle terrain of both Korea and Vietnam prompted the helicopter's widespread use during both of those wars, and technological refinements made it a valuable tool during the Persian Gulf War as well. In recent years... private industry has probably accounted for the greatest increase in helicopter use, as many companies have begun to transport their executives via helicopter. In addition, helicopter shuttle services have proliferated, particularly along the urban corridor of the American Northeast. Still, among civilians the helicopter remains best known for its medical, rescue, and relief uses.
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The tail rotor is a smaller rotor mounted vertically or near-vertical on the tail of a traditional single-rotor helicopter. The tail rotor either pushes or pulls against the tail to counter the torque. The tail rotor drive system consists of a drive shaft powered from the main transmission and a gearbox mounted at the end of the tail boom. The drive shaft may consist of one long shaft or a series of shorter shafts connected at both ends with flexible couplings. The flexible couplings allow the drive shaft to flex with the tail boom. The gearbox at the end of the tailboom provides an angled drive for the tail rotor and may ... include gearing to adjust the output to the optimum RPM for the tail rotor.
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One problem associated with helicopter rotor blades occurs because airflow along the length of each blade differs widely. This means that lift and drag fluctuate for each blade throughout the rotational cycle, thereby exerting an unsteadying influence upon the helicopter. A related problem occurs because, as the helicopter moves forward, the lift beneath the blades that enter the airstream first is high, but that beneath the blades on the opposite side of the rotor is low. The net effect of these problems is to destabilize the helicopter. Typically, the means of compensating for these unpredictable variations in lift and drag is to manufacture flexible blades connected to the rotor by a hinge. This design allows each blade to shift up or down, adjusting to changes in lift and drag.
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WASHINGTON, March 19 /PRNewswire/ -- A Vietnam combat Huey helicopter landed on the National Mall in front of the Smithsonian's National Museum of American History, on Friday, March 19. It was the culmination of a month- long, nationwide journey that began in Fort Worth, Texas. The helicopter is slated to be the central artifact of the Vietnam War section of the museum's new exhibition, "The Price of Freedom," scheduled to open on Veterans Day, Nov. 11.
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Designs are printed on the helicopter's body. The helicopter comes with a control unit and a charger and rechargeable batteries are pre-installed in the fuselage. This recall involves toys one of the following date codes: 06XXXXHM2, 06XXXXHM8, 06XXXXHM186. The date codes are located on a sticker on the bottom of the helicopter's body and on the inside of the controller's battery compartment. Toys currently on retail shelves or having a date code ending in 386 are not included in this recall.
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In 1930, the Italian engineer Corradino D'Ascanio built his D'AT3, a coaxial helicopter. His relatively large machine had two, two-bladed, counter-rotating rotors. Control was achieved by using auxiliary wings or servo-tabs on the trailing edges of the blades,[13] a concept that was later adopted by other helicopter designers, including Bleeker and Kaman. Three small propellers mounted to the airframe were used for additional pitch, roll, and yaw control. The D'AT3 held modest FAI speed and altitude records for the time, including altitude (18 m), duration (8 minutes 45 seconds) and distance flown (1,078 m).[13]
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