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Grob G 103 Twin Astir
The Grob G 103 Twin Astir is a two-seat sailplane developed in Germany in the mid 1970s based on the single-seat standard class Astir CS. Construction throughout is similar, although the wings were given a slight forward sweep (changed to a straight wing in later models).
To counter the space restrictions created by the second seat, Grob devised a novel gear retraction system for the Twin Astir. The single wheel was designed to rotate 90° sideways before retracting "flat" under the rear seat. This was only incorporated in early examples, later on, the wheel was fixed. The wheel is located ahead of the center of gravity with a tailskid in the back. Options included flight instruments for the front cockpit and water ballast.
Production continued until around 1980, when it was replaced by the Twin II, a new design not directly related to the 103.
How It Flies
The Twin Astir was designed to provide high performance for a two seat sailplane to be used in a training role and allow basic aerobatics.
Being a twin, the Astir is heavier than most of its single seat counterparts and earlier trainers, which is reflected in more inertia and stability. Its roll rate is not exceptional, even for a glider, a characteristic which was addressed in later models with improved ailerons.
When I was checking out in the Twin Astir we were doing some high angle of bank turns when a noticeable thump echoed though out the plane. I went straight and level while my instructor and I tried to figure out what had happened. Nothing seemed wrong.
Back in the landing pattern I reached down to lower the gear. It was already down. Only then did it occur to me that the thump was the gear dropping down because of the handle not being firmly in the detent.