The Duo Discus replaced the Janus as Schempp Hirth's high performance two seater trainer. Although it shares its name with the highly successful Standard Class Discus, any resemblance is only superficial. It first flew in 1993 and is still in production at the factory in Orlican in the Czech Republic. It has a 20 metre four piece wing that is slightly swept forward so that the rear pilot is close to the centre of gravity. Its best glide ratio was measured as 44:1. An optional 'turbo' retractable 2-stroke engine can be specified for extended gliding sessions. Over 500 Duo Discuses had been built by August 2007. Its chief rival is now the DG Flugzeugbau DG-1001. In U.S. Air Force service it is known as the TG-15A.
A revised model the Duo Discus X was announced in 2005. This has landing flaps incorporated into the movement of the airbrake lever to improve its approach control, giving steeper and slower approaches, it also has winglets to improve thermal flying and a sprung and lower retractable undercarriage. This makes it slightly harder to get in because the distance between the cockpit and ground is increased but the wings have a slightly higher angle of attack.
The Duo Discus XL is the latest version. It shares the same fuselage as the Schempp-Hirth Arcus and the Schempp-Hirth Nimbus 4D. The cockpit is now 10 cm longer to improve seat comfort, security, space and ergonomics. The airbrake system has been moved 4cm towards the leading edge and now extends 18mm higher. The XL is certified for simple aerobatics including spinning. It can also be flown entirely from the back seat.