Letov ST-4 Aztek

The Letov ST-4 Aztek (Aztec) is a Czech microlight aircraft that was designed and produced by Letov Kbely of Prague - Letňany, in the 1990s. When it was available, the aircraft was supplied as a complete ready-to-fly aircraft, or as a kit for amateur construction.

In January 2014, the ST-4 was no longer listed as a product of the company.

Design and development
The aircraft was designed to comply with the Fédération Aéronautique Internationale microlight category, including the category's maximum gross weight of 450 kg. The ST-4 Aztek features a strut-braced high-wing, a two-seats-in-side-by-side configuration enclosed cockpit, fixed tricycle landing gear with wheel pants, a small tailskid and a single engine in tractor configuration.

The aircraft is made from aluminum tubing with fairings made from fibreglass and its flying surfaces are covered in Dacron sailcloth. Its 10.40 m span wing mounts flaps and has a wing area of 15.21 m2. The wings are supported by V-struts with jury struts and the empennage is cable-braced. The acceptable power range is 45 to 50 hp and the standard engine used is the 50 hp Rotax 503 two-stroke powerplant. The engine is mounted high above the cockpit on the front end of the aluminum tube that acts as the tailboom.

The ST-4 Aztek has a typical empty weight of 220 kg and a gross weight of 450 kg, giving a useful load of 230 kg. With full fuel of 57 L the payload for pilot, passenger and baggage is 189 kg.

The manufacturer estimated the construction time from the supplied kit as 80 hours.

Operational history
By 1998 the company reported that 26 kits had been sold, and that 15 aircraft were completed and flying.