Editing Heading Alignment Cone

[[Image:STS-117 approach path.gif|thumb|200px|right|The HAC is cleary shown on the flight path of STS-117.]]
[[Image:Definition Spiral HAC.png|thumb|200px|right|NASA definition of the spiral HAC used for the shuttle]]
A '''Heading Alignment Cone (HAC)'''  is a virtual truncated cone, used to guide NASA's [[Space Shuttle]] onto the centerline of a runway for landing. Some publications also name it ''Heading Alignment Cylinder'', but that is not the official NASA terminology. The radius of a HAC is about 18,000 feet in  22 NM altitude. 

For alignment with the runway, the surface of the '''HAC''' is followed by the [[Shuttle]] orbiter until runway alignment is achieved, with the point, where the final glide path meets the '''HAC''', being called ''Nominal Energy Point'' (NEP).
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 For alignment with the runway, the surface of the '''HAC''' is followed by the [[Shuttle]] orbiter until runway alignment is achieved, with the point, where the final glide path meets the '''HAC''', being called ''Nominal Energy Point'' (NEP).
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