Every glider has an altimeter and a variometer. We need these instruments in our gliders to be able to assess our situation in flight. The airspeed indicator shows us the speed, the altimeter our altitude and the variometer how much you climb or sink per second. But unfortunately very few pilots actually know what is happening inside the instrument. According to our motto “Research, Build, Fly” we wanted to get to the bottom of this question by investigating how these instruments work. And who better to learn from than the manufacturer?
After meeting the Winter Brothers at AERO (Aviation Expo in Friedrichshafen) in April, they invited us to a guided tour of their factory. So we went with 15 people to the town of Jungingen on the 9th of May to have a look at the manufacture of aviation instruments on site.
Soon after arrival, we realized that the production of aviation instruments is absolute precision work. In airspeed meters, for example, a pressure diaphragm consisting of a three-hundredth of a millimeter sheet metal is installed. The gear wheels used are reminiscent of watches. But what impressed us the most was that each airspeed indicator is calibrated individually: First it is roughly adjusted so that the maximum values fit. Then a pencil is used every 10 km/h to draw a line. A line is then engraved on each of these markings and the corresponding number is engraved by hand. This is necessary because the pressure diaphragm varies slightly from instrument to instrument, so the scale can never be transferred to another. It was also interesting for us engineers how much experience and how little calculation there is behind these instruments – according to the motto “practice over theory”. For example, a new pressure diaphragm is needed for every new type of instrument. Sometimes, up to 20 different variants are tried out until a suitable one is found!
Overall, we were able to learn a lot about the instruments we use in our planes, as well as some maintenance tricks, the QNH adjustment of the altimeter for example..
We would like to thank the Winters and their employees, who all took a lot of time for us and were able to answer our many questions. Of course we hope that we can return the favor with some sightseeing flights in our gliders over Bartholomä and the Alb. Apparently none of the staff flies themselves…