But it does. At a higher wing loading the same lift drag ratio (glide angle) is obtained at a higher airspeed than for a lower gross weight.
Think about the vectors involving thrust, weight, lift and drag. At a steady glide angle all vectors form an equilibrium. Without any thrust, the forward force to overcome drag is provided by gravity and the aircraft is moving downwards with respect to the air around it. The forward motion also provides the lift to overcome the weight. If the gross weight is increased then the amount of lift needed can only be obtained at a higher airspeed. This higher airspeed can only be obtained by descending faster, and results in more drag. Interestingly, for most low drag aircraft, the best Lift:drag ratio remains the same, but is obtained at a higher airspeed for a higher gross weight. This is why gliders carry water ballast in strong conditions. The best Lift:drag ratio is obtained at a higher speed and hence gives better penetration into the wind.
Last edited by Ka6crpe; 17th August 2013 at 12:16.