Hang gliders are essentially very large kites that can hold a man aloft in midair. Though the device had been invented over a thousand years ago, it is one of only two common forms of natural flight that remains. For this type of flight, the most important statistics are:
§ Pilot skill level
§ Glider stall speed
§ Minimum Sink Speed (Min S/S)
§ Maximum Lift-to-drag Ratio (Max L/D)
§ Maximum Structural Speed (Max. S/S)
Hang gliders that require little skill generally also have a low Max L/D and a slow stall speed. With gliders of this type, it's hard to lose control of the glider, hard to stall. However, they do not fly very far, and they cannot execute high degree turns. Gliders that require a high skill level, on the other hand, are difficult to launch and make high degree of turns with only the slightest input from the pilot. In the proper hands, these gliders can stay aloft for a very long time and are highly maneuverable. The ability to ride columns of rising air is called "thermaling," while staying aloft using air currents deflected off a geological structure (such as a mountain) is called "ridge soaring." With thermaling, it is theoretically possible to attain a height of 18,000 feet. Definitions of the common hang gliding terms are listed below.
A hang glider is able to fly only when it's inherent aerodynamics are able to overcome wind resistance and gravity. At a hang glider's maximum lift-to-drag ratio, the wing surface is at its most efficient point. The L/D ratio is a mathematical representation of how many feet it can fly forward before losing a foot of altitude to gravity and drag. Thus a glider with a Max L/D of 6:1 would be able to fly twice as far as a glider whose Max L/D was 3:1, given identical wind conditions and location.
While the Max L/D of a hang glider determines the maximum flight distance, the Minimum Sink Speed determines the maximum airtime of a flight. So Max L/D gives the pilot the longest time in the air and the slowest descent.
This is a speed less than minimum sink speed, where the glider stops flying and starts falling out of the sky. Whereas some entry-level gliders act like clumsy parachutes at this point, many times the glider simply begins spiraling out of control, resulting in an accident. To recover from a stall, the pilot must make a hang-gliding proficiency check at -4 in order to recover the glider from a stall.
This is the maximum speed the glider can withstand without breaking. If the maximum speed is violated, the hang glider structure must make a successful item save versus crushing blow, each round, and penalized at -1 for every 3// above maximum speed. If the hang glider fails its structural integrity check, the keel or the crossbar breaks, causing the leading edge to collapse (and, or course, causing an accident.)