ASTS

Telemetry system for transmitting measured status variables during the winch launch

Purpose

Support for the winch operator
Improvement of winch operator training
Control of the winch tow
Improving safety
Acquisition of meteorological data
Investigation of the winch launch
Validation of theoretical models

Measured Variables (Glider)

Air speed
Altitude
GPS position
Acceleration in longitudinal and vertical direction
Rudder angle

Measured Variables (Winch)

Rope speed
Rope force

Research

Influence of towing speed, flap position and center of gravity on the towing height
Energy balance of the winch tow

Meteorology

Wind profile over altitude
Temperature profile over altitude and time

Additional Use

Mapping of thermals in the immediate vicinity of the airfield
Visualization of the aerodrome traffic

Theoretical Principles

AK-7 (Modeling of the winch launch)
Design of a fuzzy controller for winch launch (C. Wurm)

Radio Transmission

Frequency range: 869 MHz (ISM band)
Transmission power: 500 mW
Antennas: Lambda/4 antennas
Range: >2km

Details

The antenna, mounted for flight tests in the glider AK-5b (Akaflieg Karlsruhe, 1996). The transmitter unit and the pressure measuring equipment are located in the instrument panel. At the bottom right of the I-pillar there is a plug for connecting a display for calibrating the airspeed measurement and two buttons for operation. The antenna can later be fitted under the instrument panel cover or on the landing gear.

The receiver board, mounted in the AFK-3 winch (Akaflieg Karlsruhe, 1987). A similar unit is located in the aircraft as a transmitter. The receiver unit coordinates the radio traffic for several airplanes and controls the display units (see below).

The receiving antenna (cable on the right) is mounted on the roof of the winch.

Not only the direct propagation path of the radio waves is relevant for undisturbed transmission. Obstacles in an ellipsoidal area around the line of sight (Fresnel zone) also lead to losses.

The adjacent graph shows the relative loss of transmission power caused by the ground, depending on the height of the two antennas.

The display units from the winch operator’s point of view

The LED line on the right-hand side is located in the winch operator’s field of vision and displays the deviation of the towing speed from the target speed. The alphanumeric display on the left provides further information, such as the detected aircraft type and the current altitude. The target speed can also be changed manually and other settings can be made here.

An excerpt from the rule set for flight control during the climb

This is a fuzzy controller, i.e. a knowledge-based system. The designations are derived from the measured variables using a membership function (see below). Several rules can apply simultaneously.