the grob g 103 twin astir is a glass-reinforced plastic two-seat sailplane that was developed in germany in the 1970s by grob aircraft ag as a counterpart to the single-seat g 102 astir then in production. construction throughout is similar, although to preserve the centre of gravity of the design, the wings were given a slight forward sweep. while many two-seat derivatives of single-seat sailplanes have fixed undercarriage, due to the added space restrictions created by the second seat, grob devised a novel retraction system for the twin astir. the single wheel was designed to rotate 90° sideways before retracting "flat" under the rear seat, resulting in a rather unusual seating position. this was only incorporated in early examples, later on, the wheel was fixed. factory options offered to customers included whether the front seat should be equipped with flight instruments, and whether water ballast capacity should be installed.