Mind you, this answer is not grounded in the SR4 rules - I haven't played SR since 1E - but I've flow some gliders.
The key element of a glider is (usually, but not always) the lack of an engine. Most gliders have a 15:1 or better glide ratio - that is, for every 15m forward, it drops by 1m. This is usually at the cruising speed, and going faster doesn't actually improve it much, but going slower can lower it a lot. 30:1 for high performance sailplanes, and up to 65:1 for the highest performance ones. It's likely that a cargo glider would be getting near 40:1 when near empty, and 20:1 when totally filled, but you can easily increase those numbers for game purposes. (For comparison, a Cessna 172 is about 7.2:1 with the engine off, and the 747 has a peak of 17.7:1. cite) Note that hang gliders run typically in the 15:1 to 22:1 ratio at present.
Getting to altitude is the big issue. On a hot, sunny day, once you get to 100m, you can climb the rest by use of thermals even in a 15:1 glide slope aircraft. In a 30:1, like the SGS 2-32, a good hot day can cause the thermal air currents to make it hard to land! My last flight, we released at 5000', and by riding thermals in lazy (4 minute) spirals, we soon hit 10,000'. We gained 10-20' just crossing the (6-lane) highway on base-leg. (Altitude was only a few hundred feet, but when you're nose down and climbing...)
There are several launch methods in common use: cliff-launch, catapult launch, kite launch, truck tow, aircraft tow.
- In cliff-launching, you simply push it over a cliff. This is normal for hang-gliders.
- Catapult launching uses a high speed yank, and often an automatic release, to drag the airplane to launch speed. Used mostly in combination with a cliff, and mostly for sailplanes; the most frequent use is for powered aircraft off of carriers. There are several kinds, including cable & drum, pneumatic/steam ram, and magnetic accelerator. Magnetics are not yet commercially available, but are seeing US Navy use.
- Kite Launch involves high wind, a rope, and the rope being secured to the ground. As long as the wind is high enough to exceed the stall speed for the aircraft's loaded weight (including the cable weight), then you get it up to 100m or more as if it were a kite, and once the rope is tuaght and near-vertical, you pull the release, find a thermal, and go from there.
- Truck tow is a variation on kite launch. You have a truck get you to above the stall speed, so the wind is less important. Otherwise, it's the same as a kite launch.
- Airplane tow - a 10-40m cable and a friendly airplane... the airplane pulls you into the air, and you try to stay behind and just below the tow-plane. Typical release is between 3,000 and 5,000', but releases as high as 10,000' are not hard, and even 18,000 feet is doable with the right tow-plane. (Any higher requires supplemental oxygen for both, and even at 12,000', it's a good idea.)
Now, I mentioned before that not all gliders are unpowered. Some models have folding propellers, and at least 2 models have used rocket-powered launch, 3 if you count the Space Shuttle. One experimental I've seen used a motorcycle as it's ground launch (put it nose down to 90+ kts, then rotate, and hope to hit a thermal before the time you stall at 30 kts). Typically, a self-powered aircraft has enough fuel and motor to make it to about 350m (about 1000') on motor, and then glides at 20:1 or so from there.
Note also, turning does reduce the glide ratio. Not a lot, but it does.
So, to recap:
- glider glide ratio of possibly 40:1 empty, 20:1 full
- first number is forward
- second is drop, and may be omitted.
- maximum climb at speeds of about 54kph (or about 1.5m/s, or 90m/min)
- needs to be towed or kited to at least 100m
- needs a hot spot of ground to generate an updraft
- climb rates of 10-90m/minute in a good thermal
- loss to glide of 6m/min for poor (15:1) to 2.25m/min (good sailplane).