Changes

[[Image:Helicopter.jpg|400px|thumbnail|right|A [[helicopter]]]]

[[Image:Helicopter.jpg|400px|thumbnail|right|A [[helicopter]]]]

'''Aircraft''' are machines that locomote through the atmosphere. The earliest aircraft were [[kite]]s and hot air balloons. [[Dirigible]]s filled with hydrogen proved airworthy, but there was always the problem of combustion (see [[Hindenburg]] disaster).  

'''Aircraft''' are machines that locomote through the atmosphere. The earliest aircraft were [[kite]]s and hot air balloons. [[Dirigible]]s filled with [[hydrogen]] proved airworthy, but there was always the problem of combustion (see [[Hindenburg]] disaster).  

Rapid flight is made possible with a wing shape which forces the air over the wing to move faster than the air underneath. This creates a difference in air pressure, and with enough wing area a pressure differential of even one pound per square inch can add up to enough force to keep a glider in the air. The only problem then is that gliders must soon return to the earth. For an extended flight, something must pull the aircraft through the air.

Rapid flight is made possible with a wing shape which forces the air over the wing to move faster than the air underneath. This creates a difference in air pressure, and with enough wing area a pressure differential of even one pound per square inch can add up to enough force to keep a glider in the air. The only problem then is that gliders must soon return to the earth. For an extended flight, something must pull the aircraft through the air.