hey tfq, did you ever get that answer you were looking for?
In general, lift coefficient varies depending on the type of airfoil you decide to use. A good approximation, though, is that for an airfoil (an infinitely long wing), the lift curve slope will be about .11/deg of AoA. Generally, a positively cambered wing will have a zero lift coefficient at about -2 degrees AoA or so... but again, that varies from airfoil to airfoil.
Also, when you look at a real wing instead of an airfoil, the aspect ratio plays a role. Aspect ratio is wingspan divided by average chord length-- b/c-- or for a curved wing you can use wingspan squared divided by planform area-- b^2/S. Basically a measure of how long and skinny the wing is. The longer and skinnier the wing, the less lift is lost at the wingtips. That's one reason why gliders have VERY high aspect ratio wings.
Anyway, the coefficient of lift curve flattens for a real wing, depending on aspect ratio. The lower the aspect ratio, the flatter the lift curve slope. For a 757, for example, the aspect ratio is about 7.8. For an Airbus 310 its about 8.8. For a Boeing 767 its about 7.99. So you could probably use "8" as a good reference for a general airliner.
If you note the picture I've attached, a "typical" airline wing might have a lift curve slope of about .7 to .9/degree.
Now, the last factor: Angle of Attack. The biggest variation in coefficient of lift is Angle of attack. This is controlled by the pilot, and his limits are generally from the zero-lift angle of attack (typically around -2 degrees) to the stall angle of attack (typically between 12-20 degrees).
This means that an airliner (or ANY airplane for that matter) will not have 1 coefficient of lift... they'll have a range of coefficients of lift that vary with angle of attack (which in turn varies with airspeed). This range yields coefficients of lift in general between about 0 and about 1.2 or so. But the airplane could use ANY coefficient of lift in that range depending on the speed (and hence the angle of attack) it's pilot wished to fly.
Does that help?
