Glider Winch Launch Profiles using GPS

Larry Bogan
Bluenose Soaring Club - Stanley, Nova Scotia, Canada

Using a GPS (Garmin Legend) with capability of recording height along with position and time, the following profiles of a winch launch were captured. The wire 5000 ft of 1/8 inch armored cable pulled in by a gasoline engine powered winch. The measurements on the K7 launch are spaced 2 seconds apart while those for the Ka6e were 4 seconds apart. Those of the Ka6e were taken with a flight recorder which could not be adjusted to a shorter interval.

Schleicher Ka7

There was a thermal in the path of the launch on this flight and can be seen as the hump in the height versus distance curve. The angle of climb drops dramatically past the thermal core dispite the fact that the speed was kept reasonably constant.

K7 Height versus Distance K7 Climb Angle versus Distance K7 Speed versus Distance

Schleicher Ka6e

This was a smoother launch than the one above but there is 1/2 as many data points.

K6 Height versus Distance K6 Climb Angle versus Distance K6 Speed versus Distance

One important thing to notice in each of these lauches is that the angle of climb most of the time is 40 degrees or less. Many glider pilots believe they are climbing at 45 degrees or better but that is partly distorted by the fact that the angle of attack of the glider is around 5 degrees and the actual flight path is at a lower angle.